In some situations, especially when dealing with low latency on processors
supporting a variable frequency or when running inside virtual machines, each
time the process waits for an I/O using the poller, the processor goes back
to sleep or is offered to another VM for a long time, and it causes
excessively high latencies. This option provides a solution preventing the
processor from sleeping by always using a null timeout on the pollers. This
results in a significant latency reduction (30 to 100 microseconds observed)
at the expense of a risk to overheat the processor. It may even be used with
threads, in which case improperly bound threads may heavily conflict,
resulting in a worse performance and high values for the CPU stolen fields
in "show info" output, indicating which threads are misconfigured. It is
important not to let the process run on the same processor as the network
interrupts when this option is used. It is also better to avoid using it on
multiple CPU threads sharing the same core. This option is disabled by
default. If it has been enabled, it may still be forcibly disabled by
prefixing it with the "no" keyword. It is ignored by the "select" and
"poll" pollers.
This option is automatically disabled on old processes in the context of
seamless reload; it avoids too much cpu conflicts when multiple processes
stay around for some time waiting for the end of their current connections.
By default, HAProxy tries to spread the start of health checks across the
smallest health check interval of all the servers in a farm. The principle is
to avoid hammering services running on the same server. But when using large
check intervals (10 seconds or more), the last servers in the farm take some
time before starting to be tested, which can be a problem. This parameter is
used to enforce an upper bound on delay between the first and the last check,
even if the servers' check intervals are larger. When servers run with
shorter intervals, their intervals will be respected though.
Sets the maximum CPU usage HAProxy can reach before stopping the compression
for new requests or decreasing the compression level of current requests.
It works like 'maxcomprate' but measures CPU usage instead of incoming data
bandwidth. The value is expressed in percent of the CPU used by HAProxy. A
value of 100 disable the limit. The default value is 100. Setting a lower
value will prevent the compression work from slowing the whole process down
and from introducing high latencies.
Sets the maximum per-process input compression rate to <number> kilobytes
per second. For each stream, if the maximum is reached, the compression
level will be decreased during the stream. If the maximum is reached at the
beginning of a stream, the stream will not compress at all. If the maximum
is not reached, the compression level will be increased up to
tune.comp.maxlevel. A value of zero means there is no limit, this is the
default value.
Sets the maximum per-process number of concurrent connections to <number>. It
is equivalent to the command-line argument "-n". The value provided in
command-line argument via "-n" takes the precedence over the maxconn value set
in the global section. Haproxy process could be also compiled with
SYSTEM_MAXCONN compile-time variable, which is served in this case as the
system maxconn maximum. Again, the command-line "-n" argument allows at
runtime to bypass SYSTEM_MAXCONN limit, if set. Proxies will stop accepting
connections when maxconn is reached. The process soft file descriptor limit
(could be obtained with "ulimit -n" command) is automatically adjusted
according to provided maxconn. See also "
ulimit-n". Note: the "select" poller
cannot reliably use more than 1024 file descriptors on some platforms. If your
platform only supports select and reports "select FAILED" on startup, you need
to reduce the maxconn until it works (slightly below 500 in general). If
maxconn value is not set, it will be automatically calculated based on the
current file descriptors limits, reported by the "ulimit -nH" command (we take
the maximum between the hard and soft values), then automatic value will be
possibly reduced by "
fd-hard-limit" and by memory limit, if the latter was
enforced via "-m" command line option. Automatic value is also dependent from
the buffer size, memory allocated to compression, SSL cache size, and the use
or not of SSL and the associated maxsslconn (which can also be automatic).
Sets the maximum per-process number of connections per second to <number>.
Proxies will stop accepting connections when this limit is reached. It can be
used to limit the global capacity regardless of each frontend capacity. It is
important to note that this can only be used as a service protection measure,
as there will not necessarily be a fair share between frontends when the
limit is reached, so it's a good idea to also limit each frontend to some
value close to its expected share. Also, lowering tune.maxaccept can improve
fairness.
Sets the maximum per-process number of pipes to <number>. Currently, pipes
are only used by kernel-based tcp splicing. Since a pipe contains two file
descriptors, the "
ulimit-n" value will be increased accordingly. The default
value is maxconn/4, which seems to be more than enough for most heavy usages.
The splice code dynamically allocates and releases pipes, and can fall back
to standard copy, so setting this value too low may only impact performance.
Sets the maximum per-process number of sessions per second to <number>.
Proxies will stop accepting connections when this limit is reached. It can be
used to limit the global capacity regardless of each frontend capacity. It is
important to note that this can only be used as a service protection measure,
as there will not necessarily be a fair share between frontends when the
limit is reached, so it's a good idea to also limit each frontend to some
value close to its expected share. Also, lowering tune.maxaccept can improve
fairness.
Sets the maximum per-process number of concurrent SSL connections to
<number>. By default there is no SSL-specific limit, which means that the
global maxconn setting will apply to all connections. Setting this limit
avoids having openssl use too much memory and crash when malloc returns NULL
(since it unfortunately does not reliably check for such conditions). Note
that the limit applies both to incoming and outgoing connections, so one
connection which is deciphered then ciphered accounts for 2 SSL connections.
If this value is not set, but a memory limit is enforced, this value will be
automatically computed based on the memory limit, maxconn, the buffer size,
memory allocated to compression, SSL cache size, and use of SSL in either
frontends, backends or both. If neither maxconn nor maxsslconn are specified
when there is a memory limit, HAProxy will automatically adjust these values
so that 100% of the connections can be made over SSL with no risk, and will
consider the sides where it is enabled (frontend, backend, both).
Sets the maximum per-process number of SSL sessions per second to <number>.
SSL listeners will stop accepting connections when this limit is reached. It
can be used to limit the global SSL CPU usage regardless of each frontend
capacity. It is important to note that this can only be used as a service
protection measure, as there will not necessarily be a fair share between
frontends when the limit is reached, so it's a good idea to also limit each
frontend to some value close to its expected share. It is also important to
note that the sessions are accounted before they enter the SSL stack and not
after, which also protects the stack against bad handshakes. Also, lowering
tune.maxaccept can improve fairness.
Sets the maximum amount of RAM in megabytes per process usable by the zlib.
When the maximum amount is reached, future streams will not compress as long
as RAM is unavailable. When sets to 0, there is no limit.
The default value is 0. The value is available in bytes on the UNIX socket
with "show info" on the line "MaxZlibMemUsage", the memory used by zlib is
"ZlibMemUsage" in bytes.
Disables memory trimming ("malloc_trim") at a few moments where attempts are
made to reclaim lots of memory (on memory shortage or on reload). Trimming
memory forces the system's allocator to scan all unused areas and to release
them. This is generally seen as nice action to leave more available memory to
a new process while the old one is unlikely to make significant use of it.
But some systems dealing with tens to hundreds of thousands of concurrent
connections may experience a lot of memory fragmentation, that may render
this release operation extremely long. During this time, no more traffic
passes through the process, new connections are not accepted anymore, some
health checks may even fail, and the watchdog may even trigger and kill the
unresponsive process, leaving a huge core dump. If this ever happens, then it
is suggested to use this option to disable trimming and stop trying to be
nice with the new process. Note that advanced memory allocators usually do
not suffer from such a problem.
Disables the use of the "epoll" event polling system on Linux. It is
equivalent to the command-line argument "-de". The next polling system
used will generally be "poll". See also "
nopoll".
Disables the use of the event ports event polling system on SunOS systems
derived from Solaris 10 and later. It is equivalent to the command-line
argument "-dv". The next polling system used will generally be "poll". See
also "
nopoll".
Disables the use of getaddrinfo(3) for name resolving. It is equivalent to
the command line argument "-dG". Deprecated gethostbyname(3) will be used.
Disables the use of the "kqueue" event polling system on BSD. It is
equivalent to the command-line argument "-dk". The next polling system
used will generally be "poll". See also "
nopoll".
Disables the use of the "poll" event polling system. It is equivalent to the
command-line argument "-dp". The next polling system used will be "select".
It should never be needed to disable "poll" since it's available on all
platforms supported by HAProxy. See also "
nokqueue", "
noepoll" and
"
noevports".
Disables the use of SO_REUSEPORT - see socket(7). It is equivalent to the
command line argument "-dR".
Disables the use of kernel tcp splicing between sockets on Linux. It is
equivalent to the command line argument "-dS". Data will then be copied
using conventional and more portable recv/send calls. Kernel tcp splicing is
limited to some very recent instances of kernel 2.6. Most versions between
2.6.25 and 2.6.28 are buggy and will forward corrupted data, so they must not
be used. This option makes it easier to globally disable kernel splicing in
case of doubt. See also "
option splice-auto", "
option splice-request" and
"
option splice-response".
Enables ('on') or disables ('off') per-function memory profiling. This will
keep usage statistics of malloc/calloc/realloc/free calls anywhere in the
process (including libraries) which will be reported on the CLI using the
"show profiling" command. This is essentially meant to be used when an
abnormal memory usage is observed that cannot be explained by the pools and
other info are required. The performance hit will typically be around 1%,
maybe a bit more on highly threaded machines, so it is normally suitable for
use in production. The same may be achieved at run time on the CLI using the
"set profiling memory" command, please consult the management manual.
Enables ('on') or disables ('off') per-task CPU profiling. When set to 'auto'
the profiling automatically turns on a thread when it starts to suffer from
an average latency of 1000 microseconds or higher as reported in the
"avg_loop_us" activity field, and automatically turns off when the latency
returns below 990 microseconds (this value is an average over the last 1024
loops so it does not vary quickly and tends to significantly smooth short
spikes). It may also spontaneously trigger from time to time on overloaded
systems, containers, or virtual machines, or when the system swaps (which
must absolutely never happen on a load balancer).
CPU profiling per task can be very convenient to report where the time is
spent and which requests have what effect on which other request. Enabling
it will typically affect the overall's performance by less than 1%, thus it
is recommended to leave it to the default 'auto' value so that it only
operates when a problem is identified. This feature requires a system
supporting the clock_gettime(2) syscall with clock identifiers
CLOCK_MONOTONIC and CLOCK_THREAD_CPUTIME_ID, otherwise the reported time will
be zero. This option may be changed at run time using "set profiling" on the
CLI.
Sometimes it is desirable to avoid sending agent and health checks to
servers at exact intervals, for instance when many logical servers are
located on the same physical server. With the help of this parameter, it
becomes possible to add some randomness in the check interval between 0
and +/- 50%. A value between 2 and 5 seems to show good results. The
default value remains at 0.
ssl-engine <name> [algo <comma-separated list of algorithms>] Sets the OpenSSL engine to <name>. List of valid values for <name> may be
obtained using the command "openssl engine". This statement may be used
multiple times, it will simply enable multiple crypto engines. Referencing an
unsupported engine will prevent HAProxy from starting. Note that many engines
will lead to lower HTTPS performance than pure software with recent
processors. The optional command "algo" sets the default algorithms an ENGINE
will supply using the OPENSSL function ENGINE_set_default_string(). A value
of "ALL" uses the engine for all cryptographic operations. If no list of
algo is specified then the value of "ALL" is used. A comma-separated list
of different algorithms may be specified, including: RSA, DSA, DH, EC, RAND,
CIPHERS, DIGESTS, PKEY, PKEY_CRYPTO, PKEY_ASN1. This is the same format that
openssl configuration file uses:
https://www.openssl.org/docs/man1.0.2/apps/config.html
HAProxy Version 2.6 disabled the support for engines in the default build.
This option is only available when HAProxy has been built with support for
it. In case the ssl-engine is required HAProxy can be rebuild with the
USE_ENGINE=1 flag.
Adds SSL_MODE_ASYNC mode to the SSL context. This enables asynchronous TLS
I/O operations if asynchronous capable SSL engines are used. The current
implementation supports a maximum of 32 engines. The Openssl ASYNC API
doesn't support moving read/write buffers and is not compliant with
HAProxy's buffer management. So the asynchronous mode is disabled on
read/write operations (it is only enabled during initial and renegotiation
handshakes).
Sets a hard limit on the number of buffers which may be allocated per process.
The default value is zero which means unlimited. The minimum non-zero value
will always be greater than "
tune.buffers.reserve" and should ideally always
be about twice as large. Forcing this value can be particularly useful to
limit the amount of memory a process may take, while retaining a sane
behavior. When this limit is reached, streams which need a buffer wait for
another one to be released by another stream. Since buffers are dynamically
allocated and released, the waiting time is very short and not perceptible
provided that limits remain reasonable. In fact sometimes reducing the limit
may even increase performance by increasing the CPU cache's efficiency. Tests
have shown good results on average HTTP traffic with a limit to 1/10 of the
expected global maxconn setting, which also significantly reduces memory
usage. The memory savings come from the fact that a number of connections
will not allocate 2*tune.bufsize. It is best not to touch this value unless
advised to do so by an HAProxy core developer.
Sets the number of buffers which are pre-allocated and reserved for use only
during memory shortage conditions resulting in failed memory allocations. The
minimum value is 2 and is also the default. There is no reason a user would
want to change this value, it's mostly aimed at HAProxy core developers.
Sets the buffer size to this size (in bytes). Lower values allow more
streams to coexist in the same amount of RAM, and higher values allow some
applications with very large cookies to work. The default value is 16384 and
can be changed at build time. It is strongly recommended not to change this
from the default value, as very low values will break some services such as
statistics, and values larger than default size will increase memory usage,
possibly causing the system to run out of memory. At least the global maxconn
parameter should be decreased by the same factor as this one is increased. In
addition, use of HTTP/2 mandates that this value must be 16384 or more. If an
HTTP request is larger than (tune.bufsize - tune.maxrewrite), HAProxy will
return HTTP 400 (Bad Request) error. Similarly if an HTTP response is larger
than this size, HAProxy will return HTTP 502 (Bad Gateway). Note that the
value set using this parameter will automatically be rounded up to the next
multiple of 8 on 32-bit machines and 16 on 64-bit machines.
Sets the maximum compression level. The compression level affects CPU
usage during compression. This value affects CPU usage during compression.
Each stream using compression initializes the compression algorithm with
this value. The default value is 1.
Disables the data fast-forwarding. It is a mechanism to optimize the data
forwarding by passing data directly from a side to the other one without
waking the stream up. Thanks to this directive, it is possible to disable
this optimization. Note it also disable any kernel tcp splicing but also the
zero-copy forwarding. This command is not meant for regular use, it will
generally only be suggested by developers along complex debugging
sessions. For this reason it is internally marked as experimental, meaning
that "
expose-experimental-directives" must appear on a line before this
directive.
Globally disables the zero-copy forwarding of data. It is a mechanism to
optimize the data fast-forwarding by avoiding to use the channel's buffer.
Thanks to this directive, it is possible to disable this optimization. Note
it also disable any kernel tcp splicing.
Sets the number of events that may be processed at once by an asynchronous
task handler (from event_hdl API). <number> should be included between 1
and 10000. Large number could cause thread contention as a result of the
task doing heavy work without interruption, and on the other hand, small
number could result in the task being constantly rescheduled because it
cannot consume enough events per run and is not able to catch up with the
event producer. The default value may be forced at build time, otherwise
defaults to 100.
If compiled with DEBUG_FAIL_ALLOC or started with "-dMfail", gives the
percentage of chances an allocation attempt fails. Must be between 0 (no
failure) and 100 (no success). This is useful to debug and make sure memory
failures are handled gracefully. When not set, the ratio is 0. However the
command-line "-dMfail" option automatically sets it to 1% failure rate so that
it is not necessary to change the configuration for testing.
Enables ('on') or disables ('off') the edge-triggered polling mode for FDs
that support it. This is currently only support with epoll. It may noticeably
reduce the number of epoll_ctl() calls and slightly improve performance in
certain scenarios. This is still experimental, it may result in frozen
connections if bugs are still present, and is disabled by default.
Enables ('on') of disabled ('off') the zero-copy receives of data for the H1
multiplexer. It is enabled by default.
Enables ('on') of disabled ('off') the zero-copy sends of data for the H1
multiplexer. It is enabled by default.
Sets the threshold for the number of glitches on a backend connection, where
that connection will automatically be killed. This allows to automatically
kill misbehaving connections without having to write explicit rules for them.
The default value is zero, indicating that no threshold is set so that no
event will cause a connection to be closed. Beware that some H2 servers may
occasionally cause a few glitches over long lasting connection, so any non-
zero value here should probably be in the hundreds or thousands to be
effective without affecting slightly bogus servers.
Sets the HTTP/2 initial window size for outgoing connections, which is the
number of bytes the server can respond before waiting for an acknowledgment
from HAProxy. This setting only affects payload contents, not headers. When
not set, the common default value set by tune.h2.initial-window-size applies.
It can make sense to slightly increase this value to allow faster downloads
or to reduce CPU usage on the servers, at the expense of creating unfairness
between clients. It doesn't affect resource usage.
Sets the HTTP/2 maximum number of concurrent streams per outgoing connection
(i.e. the number of outstanding requests on a single connection to a server).
When not set, the default set by tune.h2.max-concurrent-streams applies. A
smaller value than the default 100 may improve a site's responsiveness at the
expense of maintaining more established connections to the servers. When the
"
http-reuse" setting is set to "always", it is recommended to reduce this
value so as not to mix too many different clients over the same connection,
because if a client is slower than others, a mechanism known as "head of
line blocking" tends to cause cascade effect on download speed for all
clients sharing a connection (keep tune.h2.be.initial-window-size low in this
case). It is highly recommended not to increase this value; some might find
it optimal to run at low values (1..5 typically).
Sets the threshold for the number of glitches on a frontend connection, where
that connection will automatically be killed. This allows to automatically
kill misbehaving connections without having to write explicit rules for them.
The default value is zero, indicating that no threshold is set so that no
event will cause a connection to be closed. Beware that some H2 clientss may
occasionally cause a few glitches over long lasting connection, so any non-
zero value here should probably be in the hundreds or thousands to be
effective without affecting slightly bogus clients.
Sets the HTTP/2 initial window size for incoming connections, which is the
number of bytes the client can upload before waiting for an acknowledgment
from HAProxy. This setting only affects payload contents (i.e. the body of
POST requests), not headers. When not set, the common default value set by
tune.h2.initial-window-size applies. It can make sense to increase this value
to allow faster uploads. The default value of 65536 allows up to 5 Mbps of
bandwidth per client over a 100 ms ping time, and 500 Mbps for 1 ms ping
time. It doesn't affect resource usage. Using too large values may cause
clients to experience a lack of responsiveness if pages are accessed in
parallel to large uploads.
Sets the HTTP/2 maximum number of concurrent streams per incoming connection
(i.e. the number of outstanding requests on a single connection from a
client). When not set, the default set by tune.h2.max-concurrent-streams
applies. A larger value than the default 100 may sometimes slightly improve
the page load time for complex sites with lots of small objects over high
latency networks but can also result in using more memory by allowing a
client to allocate more resources at once. The default value of 100 is
generally good and it is recommended not to change this value.
Sets the HTTP/2 maximum number of total streams processed per incoming
connection. Once this limit is reached, HAProxy will send a graceful GOAWAY
frame informing the client that it will close the connection after all
pending streams have been closed. In practice, clients tend to close as fast
as possible when receiving this, and to establish a new connection for next
requests. Doing this is sometimes useful and desired in situations where
clients stay connected for a very long time and cause some imbalance inside a
farm. For example, in some highly dynamic environments, it is possible that
new load balancers are instantiated on the fly to adapt to a load increase,
and that once the load goes down they should be stopped without breaking
established connections. By setting a limit here, the connections will have
a limited lifetime and will be frequently renewed, with some possibly being
established to other nodes, so that existing resources are quickly released.
It's important to understand that there is an implicit relation between this
limit and "
tune.h2.fe.max-concurrent-streams" above. Indeed, HAProxy will
always accept to process any possibly pending streams that might be in flight
between the client and the frontend, so the advertised limit will always
automatically be raised by the value configured in max-concurrent-streams,
and this value will serve as a hard limit above which a violation by a non-
compliant client will result in the connection being closed. Thus when
counting the number of requests per connection from the logs, any number
between max-total-streams and (max-total-streams + max-concurrent-streams)
may be observed depending on how fast streams are created by the client.
The default value is zero, which enforces no limit beyond those implied by
the protocol (2^30 ~= 1.07 billion). Values around 1000 may already cause
frequent connection renewal without causing any perceptible latency to most
clients. Setting it too low may result in an increase of CPU usage due to
frequent TLS reconnections, in addition to increased page load time. Please
note that some load testing tools do not support reconnections and may report
errors with this setting; as such it may be needed to disable it when running
performance benchmarks. See also "
tune.h2.fe.max-concurrent-streams".
Sets the HTTP/2 dynamic header table size. It defaults to 4096 bytes and
cannot be larger than 65536 bytes. A larger value may help certain clients
send more compact requests, depending on their capabilities. This amount of
memory is consumed for each HTTP/2 connection. It is recommended not to
change it.
Sets the default value for the HTTP/2 initial window size, on both incoming
and outgoing connections. This value is used for incoming connections when
tune.h2.fe.initial-window-size is not set, and by outgoing connections when
tune.h2.be.initial-window-size is not set. The default value is 65536, which
for uploads roughly allows up to 5 Mbps of bandwidth per client over a
network showing a 100 ms ping time, or 500 Mbps over a 1-ms local network.
Given that changing the default value will both increase upload speeds and
cause more unfairness between clients on downloads, it is recommended to
instead use the side-specific settings tune.h2.fe.initial-window-size and
tune.h2.be.initial-window-size.
Sets the default HTTP/2 maximum number of concurrent streams per connection
(i.e. the number of outstanding requests on a single connection). This value
is used for incoming connections when tune.h2.fe.max-concurrent-streams is
not set, and for outgoing connections when tune.h2.be.max-concurrent-streams
is not set. The default value is 100. The impact varies depending on the side
so please see the two settings above for more details. It is recommended not
to use this setting and to switch to the per-side ones instead. A value of
zero disables the limit so a single client may create as many streams as
allocatable by HAProxy. It is highly recommended not to change this value.
Sets the HTTP/2 maximum frame size that HAProxy announces it is willing to
receive to its peers. The default value is the largest between 16384 and the
buffer size (tune.bufsize). In any case, HAProxy will not announce support
for frame sizes larger than buffers. The main purpose of this setting is to
allow to limit the maximum frame size setting when using large buffers. Too
large frame sizes might have performance impact or cause some peers to
misbehave. It is highly recommended not to change this value.
Enables ('on') of disabled ('off') the zero-copy sends of data for the H2
multiplexer. It is enabled by default.
Sets the maximum length of captured cookies. This is the maximum value that
the "capture cookie xxx len yyy" will be allowed to take, and any upper value
will automatically be truncated to this one. It is important not to set too
high a value because all cookie captures still allocate this size whatever
their configured value (they share a same pool). This value is per request
per response, so the memory allocated is twice this value per connection.
When not specified, the limit is set to 63 characters. It is recommended not
to change this value.
Sets the maximum length of request URI in logs. This prevents truncating long
request URIs with valuable query strings in log lines. This is not related
to syslog limits. If you increase this limit, you may also increase the
'log ... len yyy' parameter. Your syslog daemon may also need specific
configuration directives too.
The default value is 1024.
Sets the maximum number of headers in a request. When a request comes with a
number of headers greater than this value (including the first line), it is
rejected with a "400 Bad Request" status code. Similarly, too large responses
are blocked with "502 Bad Gateway". The default value is 101, which is enough
for all usages, considering that the widely deployed Apache server uses the
same limit. It can be useful to push this limit further to temporarily allow
a buggy application to work by the time it gets fixed. The accepted range is
1..32767. Keep in mind that each new header consumes 32bits of memory for
each stream, so don't push this limit too high.
Enables ('on') or disables ('off') sharing of idle connection pools between
threads for a same server. The default is to share them between threads in
order to minimize the number of persistent connections to a server, and to
optimize the connection reuse rate. But to help with debugging or when
suspecting a bug in HAProxy around connection reuse, it can be convenient to
forcefully disable this idle pool sharing between multiple threads, and force
this option to "off". The default is on. It is strongly recommended against
disabling this option without setting a conservative value on "
pool-low-conn"
for all servers relying on connection reuse to achieve a high performance
level, otherwise connections might be closed very often as the thread count
increases.
Sets the duration after which HAProxy will consider that an empty buffer is
probably associated with an idle stream. This is used to optimally adjust
some packet sizes while forwarding large and small data alternatively. The
decision to use splice() or to send large buffers in SSL is modulated by this
parameter. The value is in milliseconds between 0 and 65535. A value of zero
means that HAProxy will not try to detect idle streams. The default is 1000,
which seems to correctly detect end user pauses (e.g. read a page before
clicking). There should be no reason for changing this value. Please check
tune.ssl.maxrecord below.
Normally, all "
bind" lines will create a single shard, that is, a single
socket that all threads of the process will listen to. With many threads,
this is not very efficient, and may even induce some important overhead in
the kernel for updating the polling state or even distributing events to the
various threads. Modern operating systems support balancing of incoming
connections, a mechanism that will consist in permitting multiple sockets to
be bound to the same address and port, and to evenly distribute all incoming
connections to these sockets so that each thread only sees the connections
that are waiting in the socket it is bound to. This significantly reduces
kernel-side overhead and increases performance in the incoming connection
path. This is usually enabled in HAProxy using the "
shards" setting on "
bind"
lines, which defaults to 1, meaning that each listener will be unique in the
process. On systems with many processors, it may be more convenient to change
the default setting to "by-thread" in order to always create one listening
socket per thread, or "by-group" in order to always create one listening
socket per thread group. Be careful about the file descriptor usage with
"by-thread" as each listener will need as many sockets as there are threads.
Also some operating systems (e.g. FreeBSD) are limited to no more than 256
sockets on a same address. Note that "by-group" will remain equivalent to
"by-process" for default configurations involving a single thread group, and
will fall back to sharing the same socket on systems that do not support this
mechanism. The default is "by-group" with a fallback to "by-process" for
systems or socket families that do not support multiple bindings.
Enables ('on' / 'fair') or disables ('off') the listener's multi-queue accept
which spreads the incoming traffic to all threads a "
bind" line is allowed to
run on instead of taking them for itself. This provides a smoother traffic
distribution and scales much better, especially in environments where threads
may be unevenly loaded due to external activity (network interrupts colliding
with one thread for example). The default mode, "on", optimizes the choice of
a thread by picking in a sample the one with the less connections. It is
often the best choice when connections are long-lived as it manages to keep
all threads busy. A second mode, "fair", instead cycles through all threads
regardless of their instant load level. It can be better suited for short-
lived connections, or on machines with very large numbers of threads where
the probability to find the least loaded thread with the first mode is low.
Finally it is possible to forcefully disable the redistribution mechanism
using "off" for troubleshooting, or for situations where connections are
short-lived and it is estimated that the operating system already provides a
good enough distribution. The default is "on".
This directive forces the Lua engine to execute a yield each <number> of
instructions executed. This permits interrupting a long script and allows the
HAProxy scheduler to process other tasks like accepting connections or
forwarding traffic. The default value is 10000 instructions. If HAProxy often
executes some Lua code but more responsiveness is required, this value can be
lowered. If the Lua code is quite long and its result is absolutely required
to process the data, the <number> can be increased.
Sets the maximum amount of RAM in megabytes per process usable by Lua. By
default it is zero which means unlimited. It is important to set a limit to
ensure that a bug in a script will not result in the system running out of
memory.
This is the execution timeout for the Lua sessions. This is useful for
preventing infinite loops or spending too much time in Lua. This timeout
counts only the pure Lua runtime. If the Lua does a sleep, the sleep is
not taken in account. The default timeout is 4s.
The "burst" execution timeout applies to any Lua handler. If the handler
fails to finish or yield before timeout is reached, it will be aborted to
prevent thread contention, to prevent traffic from not being served for too
long, and ultimately to prevent the process from crashing because of the
watchdog kicking in. Unlike other lua timeouts which are yield-cumulative,
burst-timeout will ensure that the time spent in a single lua execution
window does not exceed the configured timeout.
Yielding here means that the lua execution is effectively interrupted
either through an explicit call to lua-yielding function such as
core.(m)sleep() or core.yield(), or following an automatic forced-yield
(see tune.lua.forced-yield) and that it will be resumed later when the
related task is set for rescheduling. Not all lua handlers may yield: we have
to make a distinction between yieldable handlers and unyieldable handlers.
For yieldable handlers (tasks, actions..), reaching the timeout means
"
tune.lua.forced-yield" might be too high for the system, reducing it
could improve the situation, but it could also be a good idea to check if
adding manual yields at some key points within the lua function helps or not.
It may also indicate that the handler is spending too much time in a specific
lua library function that cannot be interrupted.
For unyieldable handlers (lua converters, sample fetches), it could simply
indicate that the handler is doing too much computation, which could result
from an improper design given that such handlers, which often block the
request execution flow, are expected to terminate quickly to allow the
request processing to go through. A common resolution approach here would be
to try to better optimize the lua function for speed since decreasing
"
tune.lua.forced-yield" won't help.
This timeout only counts the pure Lua runtime. If the Lua does a core.sleep,
the sleeping time is not taken in account. The default timeout is 1000ms.
Note: if a lua GC cycle is initiated from the handler (either explicitly
requested or automatically triggered by lua after some time), the GC cycle
time will also be accounted for.
Indeed, there is no way to deduce the GC cycle time, so this could lead to
some false positives on saturated systems (where GC is having hard time to
catch up and consumes most of the available execution runtime). If it were
to be the case, here are some resolution leads:
- checking if the script could be optimized to reduce lua memory footprint
- fine-tuning lua GC parameters and / or requesting manual GC cycles
(see: https://www.lua.org/manual/5.4/manual.html#pdf-collectgarbage)
- increasing tune.lua.burst-timeout
Setting value to 0 completely disables this protection.
This is the execution timeout for the Lua services. This is useful for
preventing infinite loops or spending too much time in Lua. This timeout
counts only the pure Lua runtime. If the Lua does a sleep, the sleep is
not taken in account. The default timeout is 4s.
Purpose is the same as "
tune.lua.session-timeout", but this timeout is
dedicated to the tasks. By default, this timeout isn't set because a task may
remain alive during of the lifetime of HAProxy. For example, a task used to
check servers.
Enables ('on') or disables ('off') logging the output of LUA scripts via the
loggers applicable to the current proxy, if any.
Defaults to 'on'.
Enables ('on') or disables ('off') logging the output of LUA scripts via
stderr.
When set to 'auto', logging via stderr is conditionally 'on' if any of:
- tune.lua.log.loggers is set to 'off'
- the script is executed in a non-proxy context with no global logger
- the script is executed in a proxy context with no logger attached
Please note that, when enabled, this logging is in addition to the logging
configured via tune.lua.log.loggers.
Defaults to 'auto'.
Sets the number of active checks per thread above which a thread will
actively try to search a less loaded thread to run the health check, or
queue it until the number of active checks running on it diminishes. The
default value is zero, meaning no such limit is set. It may be needed in
certain environments running an extremely large number of expensive checks
with many threads when the load appears unequal and may make health checks
to randomly time out on startup, typically when using OpenSSL 3.0 which is
about 20 times more CPU-intensive on health checks than older ones. This will
have for result to try to level the health check work across all threads. The
vast majority of configurations do not need to touch this parameter. Please
note that too low values may significantly slow down the health checking if
checks are slow to execute.
Sets the maximum number of consecutive connections a process may accept in a
row before switching to other work. In single process mode, higher numbers
used to give better performance at high connection rates, though this is not
the case anymore with the multi-queue. This value applies individually to
each listener, so that the number of processes a listener is bound to is
taken into account. This value defaults to 4 which showed best results. If a
significantly higher value was inherited from an ancient config, it might be
worth removing it as it will both increase performance and lower response
time. In multi-process mode, it is divided by twice the number of processes
the listener is bound to. Setting this value to -1 completely disables the
limitation. It should normally not be needed to tweak this value.
Sets the maximum amount of events that can be processed at once in a call to
the polling system. The default value is adapted to the operating system. It
has been noticed that reducing it below 200 tends to slightly decrease
latency at the expense of network bandwidth, and increasing it above 200
tends to trade latency for slightly increased bandwidth.
Sets the reserved buffer space to this size in bytes. The reserved space is
used for header rewriting or appending. The first reads on sockets will never
fill more than bufsize-maxrewrite. Historically it has defaulted to half of
bufsize, though that does not make much sense since there are rarely large
numbers of headers to add. Setting it too high prevents processing of large
requests or responses. Setting it too low prevents addition of new headers
to already large requests or to POST requests. It is generally wise to set it
to about 1024. It is automatically readjusted to half of bufsize if it is
larger than that. This means you don't have to worry about it when changing
bufsize.
Sets the per-thread amount of memory that will be kept hot in the local cache
and will never be recoverable by other threads. Access to this memory is very
fast (lockless), and having enough is critical to maintain a good performance
level under extreme thread contention. The value is expressed in bytes, and
the default value is configured at build time via CONFIG_HAP_POOL_CACHE_SIZE
which defaults to 524288 (512 kB). A larger value may increase performance in
some usage scenarios, especially when performance profiles show that memory
allocation is stressed a lot. Experience shows that a good value sits between
once to twice the per CPU core L2 cache size. Too large values will have a
negative impact on performance by making inefficient use of the L3 caches in
the CPUs, and will consume larger amounts of memory. It is recommended not to
change this value, or to proceed in small increments. In order to completely
disable the per-thread CPU caches, using a very small value could work, but
it is better to use "-dMno-cache" on the command-line.
Sets the size of the pattern lookup cache to <number> entries. This is an LRU
cache which reminds previous lookups and their results. It is used by ACLs
and maps on slow pattern lookups, namely the ones using the "
sub", "reg",
"dir", "dom", "end", "
bin" match methods as well as the case-insensitive
strings. It applies to pattern expressions which means that it will be able
to memorize the result of a lookup among all the patterns specified on a
configuration line (including all those loaded from files). It automatically
invalidates entries which are updated using HTTP actions or on the CLI. The
default cache size is set to 10000 entries, which limits its footprint to
about 5 MB per process/thread on 32-bit systems and 8 MB per process/thread
on 64-bit systems, as caches are thread/process local. There is a very low
risk of collision in this cache, which is in the order of the size of the
cache divided by 2^64. Typically, at 10000 requests per second with the
default cache size of 10000 entries, there's 1% chance that a brute force
attack could cause a single collision after 60 years, or 0.1% after 6 years.
This is considered much lower than the risk of a memory corruption caused by
aging components. If this is not acceptable, the cache can be disabled by
setting this parameter to 0.
Sets the maximum number of stick-table updates that haproxy will try to
process at once when sending messages. Retrieving the data for these updates
requires some locking operations which can be CPU intensive on highly
threaded machines if unbound, and may also increase the traffic latency
during the initial batched transfer between an older and a newer process.
Conversely low values may also incur higher CPU overhead, and take longer
to complete. The default value is 200 and it is suggested not to change it.
Sets the kernel pipe buffer size to this size (in bytes). By default, pipes
are the default size for the system. But sometimes when using TCP splicing,
it can improve performance to increase pipe sizes, especially if it is
suspected that pipes are not filled and that many calls to splice() are
performed. This has an impact on the kernel's memory footprint, so this must
not be changed if impacts are not understood.
This setting sets the max number of file descriptors (in percentage) used by
HAProxy globally against the maximum number of file descriptors HAProxy can
use before we start killing idle connections when we can't reuse a connection
and we have to create a new one. The default is 25 (one quarter of the file
descriptor will mean that roughly half of the maximum front connections can
keep an idle connection behind, anything beyond this probably doesn't make
much sense in the general case when targeting connection reuse).
This setting sets the max number of file descriptors (in percentage) used by
HAProxy globally against the maximum number of file descriptors HAProxy can
use before we stop putting connection into the idle pool for reuse. The
default is 20.
Enables ('on') of disabled ('off') the zero-copy forwarding of data for the
pass-through multiplexer. To be used, the kernel splicing must also be
configured. It is enabled by default.
This settings defines the maximum number of buffers allocated for a QUIC
connection on data emission. By default, it is set to 30. QUIC buffers are
drained on ACK reception. This setting has a direct impact on the throughput
and memory consumption and can be adjusted according to an estimated round
time-trip. Each buffer is tune.bufsize.
Sets the QUIC max_idle_timeout transport parameters in milliseconds for
frontends which determines the period of time after which a connection silently
closes if it has remained inactive during an effective period of time deduced
from the two max_idle_timeout values announced by the two endpoints:
- the minimum of the two values if both are not null,
- the maximum if only one of them is not null,
- if both values are null, this feature is disabled.
The default value is 30000.
Sets the QUIC initial_max_streams_bidi transport parameter for frontends.
This is the initial maximum number of bidirectional streams the remote peer
will be authorized to open. This determines the number of concurrent client
requests.
The default value is 100.
Sets the limit for which a single QUIC frame can be marked as lost. If
exceeded, the connection is considered as failing and is closed immediately.
The default value is 10.
The ratio applied to the packet reordering threshold calculated. It may
trigger a high packet loss detection when too small.
The default value is 50.
Dynamically enables the Retry feature for all the configured QUIC listeners
as soon as this number of half open connections is reached. A half open
connection is a connection whose handshake has not already successfully
completed or failed. To be functional this setting needs a cluster secret to
be set, if not it will be silently ignored (see "
cluster-secret" setting).
This setting will be also silently ignored if the use of QUIC Retry was
forced (see "
quic-force-retry").
The default value is 100.
See https://www.rfc-editor.org/rfc/rfc9000.html#section-8.1.2 for more
information about QUIC retry.
Specifies globally how QUIC connections will use socket for receive/send
operations. Connections can share listener socket or each connection can
allocate its own socket.
When default "connection" value is set, a dedicated socket will be allocated
by every QUIC connections. This option is the preferred one to achieve the
best performance with a large QUIC traffic. This is also the only way to
ensure soft-stop is conducted properly without data loss for QUIC connections
and cases of transient errors during sendto() operation are handled
efficiently. However, this relies on some advanced features from the UDP
network stack. If your platform is deemed not compatible, haproxy will
automatically switch to "listener" mode on startup. Please note that QUIC
listeners running on privileged ports may require to run as uid 0, or some
OS-specific tuning to permit the target uid to bind such ports, such as
system capabilities. See also the "
setcap" global directive.
The "listener" value indicates that QUIC transfers will occur on the shared
listener socket. This option can be a good compromise for small traffic as it
allows to reduce FD consumption. However, performance won't be optimal due to
a higher CPU usage if listeners are shared across a lot of threads or a
large number of QUIC connections can be used simultaneously.
This setting is applied in conjunction with each "
quic-socket" bind options.
If "connection" mode is used on global tuning, it will be activated for each
listener, unless its bind option is set to "listener". However, if "listener"
is used globally, it will be forced on every listener instance, regardless of
their individual configuration.
Enables ('on') of disabled ('off') the zero-copy sends of data for the QUIC
multiplexer. It is disabled by default.
For the kernel socket receive buffer size on non-connected sockets to this
size. This can be used QUIC in listener mode and log-forward on the frontend.
The default system buffers might sometimes be too small for sockets receiving
lots of aggregated traffic, causing some losses and possibly retransmits (in
case of QUIC), possibly slowing down connection establishment under heavy
traffic. The value is expressed in bytes, applied to each socket. In listener
mode, sockets are shared between all connections, and the total number of
sockets depends on the "
shards" value of the "
bind" line. There's no good
value, a good one corresponds to an expected size per connection multiplied
by the expected number of connections. The kernel may trim large values. See
also "
tune.rcvbuf.client" and "
tune.rcvbuf.server" for their connected socket
counter parts, as well as "
tune.sndbuf.backend" and "
tune.sndbuf.frontend"
for the send setting.
Forces the kernel socket receive buffer size on the client or the server side
to the specified value in bytes. This value applies to all TCP/HTTP frontends
and backends. It should normally never be set, and the default size (0) lets
the kernel auto-tune this value depending on the amount of available memory.
However it can sometimes help to set it to very low values (e.g. 4096) in
order to save kernel memory by preventing it from buffering too large amounts
of received data. Lower values will significantly increase CPU usage though.
HAProxy uses some hints to detect that a short read indicates the end of the
socket buffers. One of them is that a read returns more than <recv_enough>
bytes, which defaults to 10136 (7 segments of 1448 each). This default value
may be changed by this setting to better deal with workloads involving lots
of short messages such as telnet or SSH sessions.
Sets the maximum amount of task that can be processed at once when running
tasks. The default value depends on the number of threads but sits between 35
and 280, which tend to show the highest request rates and lowest latencies.
Increasing it may incur latency when dealing with I/Os, making it too small
can incur extra overhead. Higher thread counts benefit from lower values.
When experimenting with much larger values, it may be useful to also enable
tune.sched.low-latency and possibly tune.fd.edge-triggered to limit the
maximum latency to the lowest possible.
Enables ('on') or disables ('off') the low-latency task scheduler. By default
HAProxy processes tasks from several classes one class at a time as this is
the most efficient. But when running with large values of tune.runqueue-depth
this can have a measurable effect on request or connection latency. When this
low-latency setting is enabled, tasks of lower priority classes will always
be executed before other ones if they exist. This will permit to lower the
maximum latency experienced by new requests or connections in the middle of
massive traffic, at the expense of a higher impact on this large traffic.
For regular usage it is better to leave this off. The default value is off.
For the kernel socket send buffer size on non-connected sockets to this size.
This can be used for UNIX socket and UDP logging on the backend side, and for
QUIC in listener mode on the frontend. The default system buffers might
sometimes be too small for sockets shared between many connections (or log
senders), causing some losses and possibly retransmits, slowing down new
connection establishment under high traffic. The value is expressed in bytes,
applied to each socket. In listener mode, sockets are shared between all
connections, and the total number of sockets depends on the "
shards" value of
the "
bind" line. There's no good value, a good one corresponds to an expected
size per connection multiplied by the expected number of connections. The
kernel may trim large values. See also "
tune.sndbuf.client" and
"
tune.sndbuf.server" for their connected socket counter parts, as well as
"
tune.rcvbuf.backend" and "
tune.rcvbuf.frontend" for the receive setting.
Forces the kernel socket send buffer size on the client or the server side to
the specified value in bytes. This value applies to all TCP/HTTP frontends
and backends. It should normally never be set, and the default size (0) lets
the kernel auto-tune this value depending on the amount of available memory.
However it can sometimes help to set it to very low values (e.g. 4096) in
order to save kernel memory by preventing it from buffering too large amounts
of received data. Lower values will significantly increase CPU usage though.
Another use case is to prevent write timeouts with extremely slow clients due
to the kernel waiting for a large part of the buffer to be read before
notifying HAProxy again.
Sets the size of the global SSL session cache, in a number of blocks. A block
is large enough to contain an encoded session without peer certificate. An
encoded session with peer certificate is stored in multiple blocks depending
on the size of the peer certificate. A block uses approximately 200 bytes of
memory (based on `sizeof(struct sh_ssl_sess_hdr) + SHSESS_BLOCK_MIN_SIZE`
calculation used for `shctx_init` function). The default value may be forced
at build time, otherwise defaults to 20000. When the cache is full, the most
idle entries are purged and reassigned. Higher values reduce the occurrence
of such a purge, hence the number of CPU-intensive SSL handshakes by ensuring
that all users keep their session as long as possible. All entries are
pre-allocated upon startup. Setting this value to 0 disables the SSL session
cache.
Sets the maximum size of the buffer used for capturing client hello cipher
list, extensions list, elliptic curves list and elliptic curve point
formats. If the value is 0 (default value) the capture is disabled,
otherwise a buffer is allocated for each SSL/TLS connection.
Sets the maximum size of the Diffie-Hellman parameters used for generating
the ephemeral/temporary Diffie-Hellman key in case of DHE key exchange. The
final size will try to match the size of the server's RSA (or DSA) key (e.g,
a 2048 bits temporary DH key for a 2048 bits RSA key), but will not exceed
this maximum value. Only 1024 or higher values are allowed. Higher values
will increase the CPU load, and values greater than 1024 bits are not
supported by Java 7 and earlier clients. This value is not used if static
Diffie-Hellman parameters are supplied either directly in the certificate
file or by using the ssl-dh-param-file parameter.
If there is neither a default-dh-param nor a ssl-dh-param-file defined, and
if the server's PEM file of a given frontend does not specify its own DH
parameters, then DHE ciphers will be unavailable for this frontend.
This option disables SSL session cache sharing between all processes. It
should normally not be used since it will force many renegotiations due to
clients hitting a random process. But it may be required on some operating
systems where none of the SSL cache synchronization method may be used. In
this case, adding a first layer of hash-based load balancing before the SSL
layer might limit the impact of the lack of session sharing.
Sets the maximum amount of bytes passed to SSL_write() at any time. Default
value 0 means there is no limit. In contrast to tune.ssl.maxrecord this
settings will not be adjusted dynamically. Smaller records may decrease
throughput, but may be required when dealing with low-footprint clients.
This option activates the logging of the TLS keys. It should be used with
care as it will consume more memory per SSL session and could decrease
performances. This is disabled by default.
These sample fetches should be used to generate the SSLKEYLOGFILE that is
required to decipher traffic with wireshark.
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format
The SSLKEYLOG is a series of lines which are formatted this way:
<Label> <space> <ClientRandom> <space> <Secret>
The ClientRandom is provided by the %[ssl_fc_client_random,hex] sample
fetch, the secret and the Label could be find in the array below. You need
to generate a SSLKEYLOGFILE with all the labels in this array.
The following sample fetches are hexadecimal strings and does not need to be
converted.
SSLKEYLOGFILE Label | Sample fetches for the Secrets
--------------------------------|-----------------------------------------
CLIENT_EARLY_TRAFFIC_SECRET | %[ssl_fc_client_early_traffic_secret]
CLIENT_HANDSHAKE_TRAFFIC_SECRET | %[ssl_fc_client_handshake_traffic_secret]
SERVER_HANDSHAKE_TRAFFIC_SECRET | %[ssl_fc_server_handshake_traffic_secret]
CLIENT_TRAFFIC_SECRET_0 | %[ssl_fc_client_traffic_secret_0]
SERVER_TRAFFIC_SECRET_0 | %[ssl_fc_server_traffic_secret_0]
EXPORTER_SECRET | %[ssl_fc_exporter_secret]
EARLY_EXPORTER_SECRET | %[ssl_fc_early_exporter_secret]
This is only available with OpenSSL 1.1.1, and useful with TLS1.3 session.
If you want to generate the content of a SSLKEYLOGFILE with TLS < 1.3, you
only need this line:
"CLIENT_RANDOM %[ssl_fc_client_random,hex] %[ssl_fc_session_key,hex]"
Sets how long a cached SSL session may remain valid. This time is expressed
in seconds and defaults to 300 (5 min). It is important to understand that it
does not guarantee that sessions will last that long, because if the cache is
full, the longest idle sessions will be purged despite their configured
lifetime. The real usefulness of this setting is to prevent sessions from
being used for too long.
Sets the maximum amount of bytes passed to SSL_write() at the beginning of
the data transfer. Default value 0 means there is no limit. Over SSL/TLS,
the client can decipher the data only once it has received a full record.
With large records, it means that clients might have to download up to 16kB
of data before starting to process them. Limiting the value can improve page
load times on browsers located over high latency or low bandwidth networks.
It is suggested to find optimal values which fit into 1 or 2 TCP segments
(generally 1448 bytes over Ethernet with TCP timestamps enabled, or 1460 when
timestamps are disabled), keeping in mind that SSL/TLS add some overhead.
Typical values of 1419 and 2859 gave good results during tests. Use
"strace -e trace=write" to find the best value. HAProxy will automatically
switch to this setting after an idle stream has been detected (see
tune.idletimer above). See also tune.ssl.hard-maxrecord.
Sets the size of the cache used to store generated certificates to <number>
entries. This is a LRU cache. Because generating a SSL certificate
dynamically is expensive, they are cached. The default cache size is set to
1000 entries.
Sets the maximum interval between two automatic updates of the same OCSP
response. This time is expressed in seconds and defaults to 3600 (1 hour). It
must be set to a higher value than "
tune.ssl.ocsp-update.mindelay". See
option "
ocsp-update" for more information about the auto update mechanism.
Sets the minimum interval between two automatic updates of the same OCSP
response. This time is expressed in seconds and defaults to 300 (5 minutes).
It is particularly useful for OCSP response that do not have explicit
expiration times. It must be set to a lower value than
"
tune.ssl.ocsp-update.maxdelay". See option "
ocsp-update" for more
information about the auto update mechanism.
Sets the number of stick-counters that may be tracked at the same time by a
connection or a request via "track-sc*" actions in "
tcp-request" or
"
http-request" rules. The default value is set at build time by the macro
MAX_SESS_STK_CTR, and defaults to 3. With this setting it is possible to
change the value and ignore the one passed at build time. Increasing this
value may be needed when porting complex configurations to haproxy, but users
are warned against the costs: each entry takes 16 bytes per connection and
16 bytes per request, all of which need to be allocated and zeroed for all
requests even when not used. As such a value of 10 will inflate the memory
consumption per request by 320 bytes and will cause this memory to be erased
for each request, which does have measurable CPU impacts. Conversely, when
no "track-sc" rules are used, the value may be lowered (0 being valid to
entirely disable stick-counters).
These five tunes help to manage the maximum amount of memory used by the
variables system. "global" limits the overall amount of memory available for
all scopes. "
proc" limits the memory for the process scope, "sess" limits the
memory for the session scope, "txn" for the transaction scope, and "reqres"
limits the memory for each request or response processing.
Memory accounting is hierarchical, meaning more coarse grained limits include
the finer grained ones: "
proc" includes "sess", "sess" includes "txn", and
"txn" includes "reqres".
For example, when "
tune.vars.sess-max-size" is limited to 100,
"
tune.vars.txn-max-size" and "
tune.vars.reqres-max-size" cannot exceed
100 either. If we create a variable "txn.var" that contains 100 bytes,
all available space is consumed.
Notice that exceeding the limits at runtime will not result in an error
message, but values might be cut off or corrupted. So make sure to accurately
plan for the amount of space needed to store all your variables.
Sets the memLevel parameter in zlib initialization for each stream. It
defines how much memory should be allocated for the internal compression
state. A value of 1 uses minimum memory but is slow and reduces compression
ratio, a value of 9 uses maximum memory for optimal speed. Can be a value
between 1 and 9. The default value is 8.
Sets the window size (the size of the history buffer) as a parameter of the
zlib initialization for each stream. Larger values of this parameter result
in better compression at the expense of memory usage. Can be a value between
8 and 15. The default value is 15.
This section provides a description of each keyword and its usage.
acl <aclname> <criterion> [flags] [operator] <value> ...
Declare or complete an access list.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
This directive is only available from named defaults sections, not anonymous
ones. ACLs defined in a defaults section are not visible from other sections
using it.
Example:
acl invalid_src src 0.0.0.0/7 224.0.0.0/3
acl invalid_src src_port 0:1023
acl local_dst hdr(host) -i localhost
See
section 7 about ACL usage.
Give hints to the system about the approximate listen backlog desired size
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<conns> is the number of pending connections. Depending on the operating
system, it may represent the number of already acknowledged
connections, of non-acknowledged ones, or both.
This option is only meaningful for stream listeners, including QUIC ones. Its
behavior however is not identical with QUIC instances.
For all listeners but QUIC, in order to protect against SYN flood attacks,
one solution is to increase the system's SYN backlog size. Depending on the
system, sometimes it is just tunable via a system parameter, sometimes it is
not adjustable at all, and sometimes the system relies on hints given by the
application at the time of the listen() syscall. By default, HAProxy passes
the frontend's maxconn value to the listen() syscall. On systems which can
make use of this value, it can sometimes be useful to be able to specify a
different value, hence this backlog parameter.
On Linux 2.4, the parameter is ignored by the system. On Linux 2.6, it is
used as a hint and the system accepts up to the smallest greater power of
two, and never more than some limits (usually 32768).
For QUIC listeners, backlog sets a shared limits for both the maximum count
of active handshakes and connections waiting to be accepted. The handshake
phase relies primarily of the network latency with the remote peer, whereas
the second phase depends solely on haproxy load. When either one of this
limit is reached, haproxy starts to drop reception of INITIAL packets,
preventing any new connection allocation, until the connection excess starts
to decrease. This situation may cause browsers to silently downgrade the HTTP
versions and switching to TCP.
balance <algorithm> [ <arguments> ] Define the load balancing algorithm to be used in a backend.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<algorithm> is the algorithm used to select a server when doing load
balancing. This only applies when no persistence information
is available, or when a connection is redispatched to another
server. <algorithm> may be one of the following :
roundrobin Each server is used in turns, according to their weights.
This is the smoothest and fairest algorithm when the server's
processing time remains equally distributed. This algorithm
is dynamic, which means that server weights may be adjusted
on the fly for slow starts for instance. It is limited by
design to 4095 active servers per backend. Note that in some
large farms, when a server becomes up after having been down
for a very short time, it may sometimes take a few hundreds
requests for it to be re-integrated into the farm and start
receiving traffic. This is normal, though very rare. It is
indicated here in case you would have the chance to observe
it, so that you don't worry. Note: weights are ignored for
backends in LOG mode.
static-rr Each server is used in turns, according to their weights.
This algorithm is as similar to roundrobin except that it is
static, which means that changing a server's weight on the
fly will have no effect. On the other hand, it has no design
limitation on the number of servers, and when a server goes
up, it is always immediately reintroduced into the farm, once
the full map is recomputed. It also uses slightly less CPU to
run (around -1%). This algorithm is not usable in LOG mode.
leastconn The server with the lowest number of connections receives the
connection. Round-robin is performed within groups of servers
of the same load to ensure that all servers will be used. Use
of this algorithm is recommended where very long sessions are
expected, such as LDAP, SQL, TSE, etc... but is not very well
suited for protocols using short sessions such as HTTP. This
algorithm is dynamic, which means that server weights may be
adjusted on the fly for slow starts for instance. It will
also consider the number of queued connections in addition to
the established ones in order to minimize queuing. This
algorithm is not usable in LOG mode.
first The first server with available connection slots receives the
connection. The servers are chosen from the lowest numeric
identifier to the highest (see server parameter "id"), which
defaults to the server's position in the farm. Once a server
reaches its maxconn value, the next server is used. It does
not make sense to use this algorithm without setting maxconn.
The purpose of this algorithm is to always use the smallest
number of servers so that extra servers can be powered off
during non-intensive hours. This algorithm ignores the server
weight, and brings more benefit to long session such as RDP
or IMAP than HTTP, though it can be useful there too. In
order to use this algorithm efficiently, it is recommended
that a cloud controller regularly checks server usage to turn
them off when unused, and regularly checks backend queue to
turn new servers on when the queue inflates. Alternatively,
using "http-check send-state" may inform servers on the load.
This algorithm is not usable in LOG mode.
hash Takes a regular sample expression in argument. The expression
is evaluated for each request and hashed according to the
configured hash-type. The result of the hash is divided by
the total weight of the running servers to designate which
server will receive the request. This can be used in place of
"source", "uri", "hdr()", "url_param()", "rdp-cookie" to make
use of a converter, refine the evaluation, or be used to
extract data from local variables for example. When the data
is not available, round robin will apply. This algorithm is
static by default, which means that changing a server's
weight on the fly will have no effect, but this can be
changed using "hash-type". This algorithm is not usable for
backends in LOG mode, please use "log-hash" instead.
source The source IP address is hashed and divided by the total
weight of the running servers to designate which server will
receive the request. This ensures that the same client IP
address will always reach the same server as long as no
server goes down or up. If the hash result changes due to the
number of running servers changing, many clients will be
directed to a different server. This algorithm is generally
used in TCP mode where no cookie may be inserted. It may also
be used on the Internet to provide a best-effort stickiness
to clients which refuse session cookies. This algorithm is
static by default, which means that changing a server's
weight on the fly will have no effect, but this can be
changed using "hash-type". See also the "hash" option above.
This algorithm is not usable for backends in LOG mode.
uri This algorithm hashes either the left part of the URI (before
the question mark) or the whole URI (if the "whole" parameter
is present) and divides the hash value by the total weight of
the running servers. The result designates which server will
receive the request. This ensures that the same URI will
always be directed to the same server as long as no server
goes up or down. This is used with proxy caches and
anti-virus proxies in order to maximize the cache hit rate.
Note that this algorithm may only be used in an HTTP backend.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
This algorithm supports two optional parameters "len" and
"depth", both followed by a positive integer number. These
options may be helpful when it is needed to balance servers
based on the beginning of the URI only. The "len" parameter
indicates that the algorithm should only consider that many
characters at the beginning of the URI to compute the hash.
Note that having "len" set to 1 rarely makes sense since most
URIs start with a leading "/".
The "depth" parameter indicates the maximum directory depth
to be used to compute the hash. One level is counted for each
slash in the request. If both parameters are specified, the
evaluation stops when either is reached.
A "path-only" parameter indicates that the hashing key starts
at the first '/' of the path. This can be used to ignore the
authority part of absolute URIs, and to make sure that HTTP/1
and HTTP/2 URIs will provide the same hash. See also the
"hash" option above.
url_param The URL parameter specified in argument will be looked up in
the query string of each HTTP GET request.
If the modifier "check_post" is used, then an HTTP POST
request entity will be searched for the parameter argument,
when it is not found in a query string after a question mark
('?') in the URL. The message body will only start to be
analyzed once either the advertised amount of data has been
received or the request buffer is full. In the unlikely event
that chunked encoding is used, only the first chunk is
scanned. Parameter values separated by a chunk boundary, may
be randomly balanced if at all. This keyword used to support
an optional <max_wait> parameter which is now ignored.
If the parameter is found followed by an equal sign ('=') and
a value, then the value is hashed and divided by the total
weight of the running servers. The result designates which
server will receive the request.
This is used to track user identifiers in requests and ensure
that a same user ID will always be sent to the same server as
long as no server goes up or down. If no value is found or if
the parameter is not found, then a round robin algorithm is
applied. Note that this algorithm may only be used in an HTTP
backend. This algorithm is static by default, which means
that changing a server's weight on the fly will have no
effect, but this can be changed using "hash-type". See also
the "hash" option above.
hdr(<name>) The HTTP header <name> will be looked up in each HTTP
request. Just as with the equivalent ACL 'hdr()' function,
the header name in parenthesis is not case sensitive. If the
header is absent or if it does not contain any value, the
roundrobin algorithm is applied instead.
An optional 'use_domain_only' parameter is available, for
reducing the hash algorithm to the main domain part with some
specific headers such as 'Host'. For instance, in the Host
value "haproxy.1wt.eu", only "1wt" will be considered.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type". See also the
"hash" option above.
random
random(<draws>)
A random number will be used as the key for the consistent
hashing function. This means that the servers' weights are
respected, dynamic weight changes immediately take effect, as
well as new server additions. Random load balancing can be
useful with large farms or when servers are frequently added
or removed as it may avoid the hammering effect that could
result from roundrobin or leastconn in this situation. The
hash-balance-factor directive can be used to further improve
fairness of the load balancing, especially in situations
where servers show highly variable response times. When an
argument <draws> is present, it must be an integer value one
or greater, indicating the number of draws before selecting
the least loaded of these servers. It was indeed demonstrated
that picking the least loaded of two servers is enough to
significantly improve the fairness of the algorithm, by
always avoiding to pick the most loaded server within a farm
and getting rid of any bias that could be induced by the
unfair distribution of the consistent list. Higher values N
will take away N-1 of the highest loaded servers at the
expense of performance. With very high values, the algorithm
will converge towards the leastconn's result but much slower.
The default value is 2, which generally shows very good
distribution and performance. This algorithm is also known as
the Power of Two Random Choices and is described here :
http://www.eecs.harvard.edu/~michaelm/postscripts/handbook2001.pdf
For backends in LOG mode, the number of draws is ignored and
a single random is picked since there is no notion of server
load. Random log balancing can be useful with large farms or
when servers are frequently added or removed from the pool of
available servers as it may avoid the hammering effect that
could result from roundrobin in this situation.
rdp-cookie
rdp-cookie(<name>)
The RDP cookie <name> (or "mstshash" if omitted) will be
looked up and hashed for each incoming TCP request. Just as
with the equivalent ACL 'req.rdp_cookie()' function, the name
is not case-sensitive. This mechanism is useful as a degraded
persistence mode, as it makes it possible to always send the
same user (or the same session ID) to the same server. If the
cookie is not found, the normal roundrobin algorithm is
used instead.
Note that for this to work, the frontend must ensure that an
RDP cookie is already present in the request buffer. For this
you must use 'tcp-request content accept' rule combined with
a 'req.rdp_cookie_cnt' ACL.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type". See also the
"hash" option above.
log-hash Takes a comma-delimited list of converters in argument. These
converters are applied in sequence to the input log message,
and the result will be cast as a string then hashed according
to the configured hash-type. The resulting hash will be used
to select the destination server among the ones declared in
the log backend. The goal of this algorithm is to be able to
extract a key within the final log message using string
converters and then be able to stick to the same server thanks
to the hash. Only "map-based" hashes are supported for now.
This algorithm is only usable for backends in LOG mode, for
others, please use "hash" instead.
sticky Tries to stick to the same server as much as possible. The
first server in the list of available servers receives all
the log messages. When the server goes DOWN, the next server
in the list takes its place. When a previously DOWN server
goes back UP it is added at the end of the list so that the
sticky server doesn't change until it becomes DOWN. This
algorithm is only usable for backends in LOG mode.
<arguments> is an optional list of arguments which may be needed by some
algorithms. Right now, only "url_param", "uri" and "log-hash"
support an optional argument.
The load balancing algorithm of a backend is set to roundrobin when no other
algorithm, mode nor option have been set. The algorithm may only be set once
for each backend. In backends in LOG mode, server "
weight" is always ignored.
With authentication schemes that require the same connection like NTLM, URI
based algorithms must not be used, as they would cause subsequent requests
to be routed to different backend servers, breaking the invalid assumptions
NTLM relies on.
TCP/HTTP Examples :
balance roundrobin
balance url_param userid
balance url_param session_id check_post 64
balance hdr(User-Agent)
balance hdr(host)
balance hdr(Host) use_domain_only
balance hash req.cookie(clientid)
balance hash var(req.client_id)
balance hash req.hdr_ip(x-forwarded-for,-1),ipmask(24)
LOG backend examples:
global
log backend@mylog-rrb local0 # send all logs to mylog-rrb backend
log backend@mylog-hash local0 # send all logs to mylog-hash backend
backend mylog-rrb
mode log
balance roundrobin
server s1 udp@127.0.0.1:514 # will receive 50% of log messages
server s2 udp@127.0.0.1:514
backend mylog-hash
mode log
# extract "METHOD URL PROTO" at the end of the log message,
# and let haproxy hash it so that log messages generated from
# similar requests get sent to the same syslog server:
balance log-hash 'field(-2,\")'
# server list here
server s1 127.0.0.1:514
#...
Note: the following caveats and limitations on using the "check_post"
extension with "
url_param" must be considered :
- all POST requests are eligible for consideration, because there is no way
to determine if the parameters will be found in the body or entity which
may contain binary data. Therefore another method may be required to
restrict consideration of POST requests that have no URL parameters in
the body. (see acl http_end)
- using a <max_wait> value larger than the request buffer size does not
make sense and is useless. The buffer size is set at build time, and
defaults to 16 kB.
- Content-Encoding is not supported, the parameter search will probably
fail; and load balancing will fall back to Round Robin.
- Expect: 100-continue is not supported, load balancing will fall back to
Round Robin.
- Transfer-Encoding (RFC7230 3.3.1) is only supported in the first chunk.
If the entire parameter value is not present in the first chunk, the
selection of server is undefined (actually, defined by how little
actually appeared in the first chunk).
- This feature does not support generation of a 100, 411 or 501 response.
- In some cases, requesting "check_post" MAY attempt to scan the entire
contents of a message body. Scanning normally terminates when linear
white space or control characters are found, indicating the end of what
might be a URL parameter list. This is probably not a concern with SGML
type message bodies.
bind [<address>]:
<port_range> [, ...] [param*] bind /
<path> [, ...] [param*] Define one or several listening addresses and/or ports in a frontend.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<address> is optional and can be a host name, an IPv4 address, an IPv6
address, or '*'. It designates the address the frontend will
listen on. If unset, all IPv4 addresses of the system will be
listened on. The same will apply for '*' or the system's
special address "0.0.0.0". The IPv6 equivalent is '::'. Note
that for UDP, specific OS features are required when binding
on multiple addresses to ensure the correct network interface
and source address will be used on response. In other way,
for QUIC listeners only bind on multiple addresses if running
with a modern enough systems.
Optionally, an address family prefix may be used before the
address to force the family regardless of the address format,
which can be useful to specify a path to a unix socket with
no slash ('/'). Currently supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'udp@' -> address is resolved as IPv4 or IPv6 and
protocol UDP is used. Currently those listeners are
supported only in log-forward sections.
- 'udp4@' -> address is always IPv4 and protocol UDP
is used. Currently those listeners are supported
only in log-forward sections.
- 'udp6@' -> address is always IPv6 and protocol UDP
is used. Currently those listeners are supported
only in log-forward sections.
- 'unix@' -> address is a path to a local unix socket
- 'abns@' -> address is in abstract namespace (Linux only).
- 'fd@<n>' -> use file descriptor <n> inherited from the
parent. The fd must be bound and may or may not already
be listening.
- 'sockpair@<n>'-> like fd@ but you must use the fd of a
connected unix socket or of a socketpair. The bind waits
to receive a FD over the unix socket and uses it as if it
was the FD of an accept(). Should be used carefully.
- 'quic4@' -> address is resolved as IPv4 and protocol UDP
is used. Note that to achieve the best performance with a
large traffic you should keep "tune.quic.socket-owner" on
connection. Else QUIC connections will be multiplexed
over the listener socket. Another alternative would be to
duplicate QUIC listener instances over several threads,
for example using "shards" keyword to at least reduce
thread contention.
- 'quic6@' -> address is resolved as IPv6 and protocol UDP
is used. The performance note for QUIC over IPv4 applies
as well.
- 'rhttp@' [ EXPERIMENTAL ] -> used for reverse HTTP.
Address must be a server with the format
'<backend>/<server>'. The server will be used to
instantiate connections to a remote address. The listener
will try to maintain "nbconn" connections. This is an
experimental features which requires
"expose-experimental-directives" on a line before this
bind.
You may want to reference some environment variables in the
address parameter, see section 2.3 about environment
variables.
<port_range> is either a unique TCP port, or a port range for which the
proxy will accept connections for the IP address specified
above. The port is mandatory for TCP listeners. Note that in
the case of an IPv6 address, the port is always the number
after the last colon (':'). A range can either be :
- a numerical port (ex: '80')
- a dash-delimited ports range explicitly stating the lower
and upper bounds (ex: '2000-2100') which are included in
the range.
Particular care must be taken against port ranges, because
every <address:port> couple consumes one socket (= a file
descriptor), so it's easy to consume lots of descriptors
with a simple range, and to run out of sockets. Also, each
<address:port> couple must be used only once among all
instances running on a same system. Please note that binding
to ports lower than 1024 generally require particular
privileges to start the program, which are independent of
the 'uid' parameter.
<path> is a UNIX socket path beginning with a slash ('/'). This is
alternative to the TCP listening port. HAProxy will then
receive UNIX connections on the socket located at this place.
The path must begin with a slash and by default is absolute.
It can be relative to the prefix defined by "unix-bind" in
the global section. Note that the total length of the prefix
followed by the socket path cannot exceed some system limits
for UNIX sockets, which commonly are set to 107 characters.
<param*> is a list of parameters common to all sockets declared on the
same line. These numerous parameters depend on OS and build
options and have a complete section dedicated to them. Please
refer to section 5 to for more details.
It is possible to specify a list of address:port combinations delimited by
commas. The frontend will then listen on all of these addresses. There is no
fixed limit to the number of addresses and ports which can be listened on in
a frontend, as well as there is no limit to the number of "
bind" statements
in a frontend.
Example :
listen http_proxy
bind :80,:443
bind 10.0.0.1:10080,10.0.0.1:10443
bind /var/run/ssl-frontend.sock user root mode 600 accept-proxy
listen http_https_proxy
bind :80
bind :443 ssl crt /etc/haproxy/site.pem
listen http_https_proxy_explicit
bind ipv6@:80
bind ipv4@public_ssl:443 ssl crt /etc/haproxy/site.pem
bind unix@ssl-frontend.sock user root mode 600 accept-proxy
listen external_bind_app1
bind "fd@${FD_APP1}"
listen h3_quic_proxy
bind quic4@10.0.0.1:8888 ssl crt /etc/mycrt
Note: regarding Linux's abstract namespace sockets, HAProxy uses the whole
sun_path length is used for the address length. Some other programs
such as socat use the string length only by default. Pass the option
",unix-tightsocklen=0" to any abstract socket definition in socat to
make it compatible with HAProxy's.
Capture and log a cookie in the request and in the response.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the beginning of the name of the cookie to capture. In order
to match the exact name, simply suffix the name with an equal
sign ('='). The full name will appear in the logs, which is
useful with application servers which adjust both the cookie name
and value (e.g. ASPSESSIONXXX).
<length> is the maximum number of characters to report in the logs, which
include the cookie name, the equal sign and the value, all in the
standard "name=value" form. The string will be truncated on the
right if it exceeds <length>.
Only the first cookie is captured. Both the "
cookie" request headers and the
"
set-cookie" response headers are monitored. This is particularly useful to
check for application bugs causing session crossing or stealing between
users, because generally the user's cookies can only change on a login page.
When the cookie was not presented by the client, the associated log column
will report "-". When a request does not cause a cookie to be assigned by the
server, a "-" is reported in the response column.
The capture is performed in the frontend only because it is necessary that
the log format does not change for a given frontend depending on the
backends. This may change in the future. Note that there can be only one
"
capture cookie" statement in a frontend. The maximum capture length is set
by the global "
tune.http.cookielen" setting and defaults to 63 characters. It
is not possible to specify a capture in a "defaults" section.
Example:
capture cookie ASPSESSION len 32
Capture and log the last occurrence of the specified request header.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the name of the header to capture. The header names are not
case-sensitive, but it is a common practice to write them as they
appear in the requests, with the first letter of each word in
upper case. The header name will not appear in the logs, only the
value is reported, but the position in the logs is respected.
<length> is the maximum number of characters to extract from the value and
report in the logs. The string will be truncated on the right if
it exceeds <length>.
The complete value of the last occurrence of the header is captured. The
value will be added to the logs between braces ('{}'). If multiple headers
are captured, they will be delimited by a vertical bar ('|') and will appear
in the same order they were declared in the configuration. Non-existent
headers will be logged just as an empty string. Common uses for request
header captures include the "Host" field in virtual hosting environments, the
"Content-length" when uploads are supported, "User-agent" to quickly
differentiate between real users and robots, and "X-Forwarded-For" in proxied
environments to find where the request came from.
Note that when capturing headers such as "User-agent", some spaces may be
logged, making the log analysis more difficult. Thus be careful about what
you log if you know your log parser is not smart enough to rely on the
braces.
There is no limit to the number of captured request headers nor to their
length, though it is wise to keep them low to limit memory usage per stream.
In order to keep log format consistent for a same frontend, header captures
can only be declared in a frontend. It is not possible to specify a capture
in a "defaults" section.
Example:
capture request header Host len 15
capture request header X-Forwarded-For len 15
capture request header Referer len 15
Capture and log the last occurrence of the specified response header.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the name of the header to capture. The header names are not
case-sensitive, but it is a common practice to write them as they
appear in the response, with the first letter of each word in
upper case. The header name will not appear in the logs, only the
value is reported, but the position in the logs is respected.
<length> is the maximum number of characters to extract from the value and
report in the logs. The string will be truncated on the right if
it exceeds <length>.
The complete value of the last occurrence of the header is captured. The
result will be added to the logs between braces ('{}') after the captured
request headers. If multiple headers are captured, they will be delimited by
a vertical bar ('|') and will appear in the same order they were declared in
the configuration. Non-existent headers will be logged just as an empty
string. Common uses for response header captures include the "Content-length"
header which indicates how many bytes are expected to be returned, the
"Location" header to track redirections.
There is no limit to the number of captured response headers nor to their
length, though it is wise to keep them low to limit memory usage per stream.
In order to keep log format consistent for a same frontend, header captures
can only be declared in a frontend. It is not possible to specify a capture
in a "defaults" section.
Example:
capture response header Content-length len 9
capture response header Location len 15
Sets the maximum number of keepalive probes TCP should send before dropping
the connection on the client side.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<count> is the maximum number of keepalive probes.
This keyword corresponds to the socket option TCP_KEEPCNT. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_probes) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
Sets the time the connection needs to remain idle before TCP starts sending
keepalive probes, if enabled the sending of TCP keepalive packets on the
client side.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the time the connection needs to remain idle before TCP starts
sending keepalive probes. It is specified in seconds by default,
but can be in any other unit if the number is suffixed by the
unit, as explained at the top of this document.
This keyword corresponds to the socket option TCP_KEEPIDLE. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_time) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
Sets the time between individual keepalive probes on the client side.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the time between individual keepalive probes. It is specified
in seconds by default, but can be in any other unit if the number
is suffixed by the unit, as explained at the top of this
document.
This keyword corresponds to the socket option TCP_KEEPINTVL. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_intvl) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
Enable HTTP compression.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :algo is followed by the list of supported compression algorithms for
responses (legacy keyword)
algo-req is followed by compression algorithm for request (only one is
provided).
algo-res is followed by the list of supported compression algorithms for
responses.
type is followed by the list of MIME types that will be compressed for
responses (legacy keyword).
type-req is followed by the list of MIME types that will be compressed for
requests.
type-res is followed by the list of MIME types that will be compressed for
responses.
The currently supported algorithms are :
identity this is mostly for debugging, and it was useful for developing
the compression feature. Identity does not apply any change on
data.
gzip applies gzip compression. This setting is only available when
support for zlib or libslz was built in.
deflate same as "gzip", but with deflate algorithm and zlib format.
Note that this algorithm has ambiguous support on many
browsers and no support at all from recent ones. It is
strongly recommended not to use it for anything else than
experimentation. This setting is only available when support
for zlib or libslz was built in.
raw-deflate same as "deflate" without the zlib wrapper, and used as an
alternative when the browser wants "deflate". All major
browsers understand it and despite violating the standards,
it is known to work better than "deflate", at least on MSIE
and some versions of Safari. Do not use it in conjunction
with "deflate", use either one or the other since both react
to the same Accept-Encoding token. This setting is only
available when support for zlib or libslz was built in.
Compression will be activated depending on the Accept-Encoding request
header. With identity, it does not take care of that header.
If backend servers support HTTP compression, these directives
will be no-op: HAProxy will see the compressed response and will not
compress again. If backend servers do not support HTTP compression and
there is Accept-Encoding header in request, HAProxy will compress the
matching response.
Compression is disabled when:
* the request does not advertise a supported compression algorithm in the
"Accept-Encoding" header
* the response message is not HTTP/1.1 or above
* HTTP status code is not one of 200, 201, 202, or 203
* response contain neither a "Content-Length" header nor a
"Transfer-Encoding" whose last value is "chunked"
* response contains a "Content-Type" header whose first value starts with
"multipart"
* the response contains the "no-transform" value in the "Cache-control"
header
* User-Agent matches "Mozilla/4" unless it is MSIE 6 with XP SP2, or MSIE 7
and later
* The response contains a "Content-Encoding" header, indicating that the
response is already compressed (see compression offload)
* The response contains an invalid "ETag" header or multiple ETag headers
Note: The compression does not emit the Warning header.
Examples :
compression algo gzip
compression type text/html text/plain
Makes HAProxy work as a compression offloader only.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
The "offload" setting makes HAProxy remove the Accept-Encoding header to
prevent backend servers from compressing responses. It is strongly
recommended not to do this because this means that all the compression work
will be done on the single point where HAProxy is located. However in some
deployment scenarios, HAProxy may be installed in front of a buggy gateway
with broken HTTP compression implementation which can't be turned off.
In that case HAProxy can be used to prevent that gateway from emitting
invalid payloads. In this case, simply removing the header in the
configuration does not work because it applies before the header is parsed,
so that prevents HAProxy from compressing. The "offload" setting should
then be used for such scenarios.
If this setting is used in a defaults section, a warning is emitted and the
option is ignored.
Makes haproxy able to compress both requests and responses.
Valid values are "request", to compress only requests, "response", to
compress only responses, or "both", when you want to compress both.
The default value is "response".
May be used in the following contexts: http
cookie <name> [ rewrite | insert | prefix ] [ indirect ] [ nocache ]
[ postonly ] [ preserve ] [ httponly ] [ secure ]
[ domain <domain> ]*
[ maxidle <idle> ] [ maxlife <life> ]
[ dynamic ] [ attr <value> ]*
Enable cookie-based persistence in a backend.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the name of the cookie which will be monitored, modified or
inserted in order to bring persistence. This cookie is sent to
the client via a "Set-Cookie" header in the response, and is
brought back by the client in a "Cookie" header in all requests.
Special care should be taken to choose a name which does not
conflict with any likely application cookie. Also, if the same
backends are subject to be used by the same clients (e.g.
HTTP/HTTPS), care should be taken to use different cookie names
between all backends if persistence between them is not desired.
rewrite This keyword indicates that the cookie will be provided by the
server and that HAProxy will have to modify its value to set the
server's identifier in it. This mode is handy when the management
of complex combinations of "Set-cookie" and "Cache-control"
headers is left to the application. The application can then
decide whether or not it is appropriate to emit a persistence
cookie. Since all responses should be monitored, this mode
doesn't work in HTTP tunnel mode. Unless the application
behavior is very complex and/or broken, it is advised not to
start with this mode for new deployments. This keyword is
incompatible with "insert" and "prefix".
insert This keyword indicates that the persistence cookie will have to
be inserted by HAProxy in server responses if the client did not
already have a cookie that would have permitted it to access this
server. When used without the "preserve" option, if the server
emits a cookie with the same name, it will be removed before
processing. For this reason, this mode can be used to upgrade
existing configurations running in the "rewrite" mode. The cookie
will only be a session cookie and will not be stored on the
client's disk. By default, unless the "indirect" option is added,
the server will see the cookies emitted by the client. Due to
caching effects, it is generally wise to add the "nocache" or
"postonly" keywords (see below). The "insert" keyword is not
compatible with "rewrite" and "prefix".
prefix This keyword indicates that instead of relying on a dedicated
cookie for the persistence, an existing one will be completed.
This may be needed in some specific environments where the client
does not support more than one single cookie and the application
already needs it. In this case, whenever the server sets a cookie
named <name>, it will be prefixed with the server's identifier
and a delimiter. The prefix will be removed from all client
requests so that the server still finds the cookie it emitted.
Since all requests and responses are subject to being modified,
this mode doesn't work with tunnel mode. The "prefix" keyword is
not compatible with "rewrite" and "insert". Note: it is highly
recommended not to use "indirect" with "prefix", otherwise server
cookie updates would not be sent to clients.
indirect When this option is specified, no cookie will be emitted to a
client which already has a valid one for the server which has
processed the request. If the server sets such a cookie itself,
it will be removed, unless the "preserve" option is also set. In
"insert" mode, this will additionally remove cookies from the
requests transmitted to the server, making the persistence
mechanism totally transparent from an application point of view.
Note: it is highly recommended not to use "indirect" with
"prefix", otherwise server cookie updates would not be sent to
clients.
nocache This option is recommended in conjunction with the insert mode
when there is a cache between the client and HAProxy, as it
ensures that a cacheable response will be tagged non-cacheable if
a cookie needs to be inserted. This is important because if all
persistence cookies are added on a cacheable home page for
instance, then all customers will then fetch the page from an
outer cache and will all share the same persistence cookie,
leading to one server receiving much more traffic than others.
See also the "insert" and "postonly" options.
postonly This option ensures that cookie insertion will only be performed
on responses to POST requests. It is an alternative to the
"nocache" option, because POST responses are not cacheable, so
this ensures that the persistence cookie will never get cached.
Since most sites do not need any sort of persistence before the
first POST which generally is a login request, this is a very
efficient method to optimize caching without risking to find a
persistence cookie in the cache.
See also the "insert" and "nocache" options.
preserve This option may only be used with "insert" and/or "indirect". It
allows the server to emit the persistence cookie itself. In this
case, if a cookie is found in the response, HAProxy will leave it
untouched. This is useful in order to end persistence after a
logout request for instance. For this, the server just has to
emit a cookie with an invalid value (e.g. empty) or with a date in
the past. By combining this mechanism with the "disable-on-404"
check option, it is possible to perform a completely graceful
shutdown because users will definitely leave the server after
they logout.
httponly This option tells HAProxy to add an "HttpOnly" cookie attribute
when a cookie is inserted. This attribute is used so that a
user agent doesn't share the cookie with non-HTTP components.
Please check RFC6265 for more information on this attribute.
secure This option tells HAProxy to add a "Secure" cookie attribute when
a cookie is inserted. This attribute is used so that a user agent
never emits this cookie over non-secure channels, which means
that a cookie learned with this flag will be presented only over
SSL/TLS connections. Please check RFC6265 for more information on
this attribute.
domain This option allows to specify the domain at which a cookie is
inserted. It requires exactly one parameter: a valid domain
name. If the domain begins with a dot, the browser is allowed to
use it for any host ending with that name. It is also possible to
specify several domain names by invoking this option multiple
times. Some browsers might have small limits on the number of
domains, so be careful when doing that. For the record, sending
10 domains to MSIE 6 or Firefox 2 works as expected.
maxidle This option allows inserted cookies to be ignored after some idle
time. It only works with insert-mode cookies. When a cookie is
sent to the client, the date this cookie was emitted is sent too.
Upon further presentations of this cookie, if the date is older
than the delay indicated by the parameter (in seconds), it will
be ignored. Otherwise, it will be refreshed if needed when the
response is sent to the client. This is particularly useful to
prevent users who never close their browsers from remaining for
too long on the same server (e.g. after a farm size change). When
this option is set and a cookie has no date, it is always
accepted, but gets refreshed in the response. This maintains the
ability for admins to access their sites. Cookies that have a
date in the future further than 24 hours are ignored. Doing so
lets admins fix timezone issues without risking kicking users off
the site.
maxlife This option allows inserted cookies to be ignored after some life
time, whether they're in use or not. It only works with insert
mode cookies. When a cookie is first sent to the client, the date
this cookie was emitted is sent too. Upon further presentations
of this cookie, if the date is older than the delay indicated by
the parameter (in seconds), it will be ignored. If the cookie in
the request has no date, it is accepted and a date will be set.
Cookies that have a date in the future further than 24 hours are
ignored. Doing so lets admins fix timezone issues without risking
kicking users off the site. Contrary to maxidle, this value is
not refreshed, only the first visit date counts. Both maxidle and
maxlife may be used at the time. This is particularly useful to
prevent users who never close their browsers from remaining for
too long on the same server (e.g. after a farm size change). This
is stronger than the maxidle method in that it forces a
redispatch after some absolute delay.
dynamic Activate dynamic cookies. When used, a session cookie is
dynamically created for each server, based on the IP and port
of the server, and a secret key, specified in the
"dynamic-cookie-key" backend directive.
The cookie will be regenerated each time the IP address change,
and is only generated for IPv4/IPv6.
attr This option tells HAProxy to add an extra attribute when a
cookie is inserted. The attribute value can contain any
characters except control ones or ";". This option may be
repeated.
There can be only one persistence cookie per HTTP backend, and it can be
declared in a defaults section. The value of the cookie will be the value
indicated after the "
cookie" keyword in a "
server" statement. If no cookie
is declared for a given server, the cookie is not set.
Examples :
cookie JSESSIONID prefix
cookie SRV insert indirect nocache
cookie SRV insert postonly indirect
cookie SRV insert indirect nocache maxidle 30m maxlife 8h
Declares a capture slot.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments:<length> is the length allowed for the capture.
This declaration is only available in the frontend or listen section, but the
reserved slot can be used in the backends. The "request" keyword allocates a
capture slot for use in the request, and "response" allocates a capture slot
for use in the response.
Change default options for a server in a backend
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments:<param*> is a list of parameters for this server. The "default-server"
keyword accepts an important number of options and has a complete
section dedicated to it. Please refer to section 5 for more
details.
Example :
default-server inter 1000 weight 13
Specify the backend to use when no "
use_backend" rule has been matched.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<backend> is the name of the backend to use.
When doing content-switching between frontend and backends using the
"
use_backend" keyword, it is often useful to indicate which backend will be
used when no rule has matched. It generally is the dynamic backend which
will catch all undetermined requests.
Example :
use_backend dynamic if url_dyn
use_backend static if url_css url_img extension_img
default_backend dynamic
Describe a listen, frontend or backend.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments : string
Allows to add a sentence to describe the related object in the HAProxy HTML
stats page. The description will be printed on the right of the object name
it describes.
No need to backslash spaces in the <string> arguments.
Disable a proxy, frontend or backend.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
The "
disabled" keyword is used to disable an instance, mainly in order to
liberate a listening port or to temporarily disable a service. The instance
will still be created and its configuration will be checked, but it will be
created in the "stopped" state and will appear as such in the statistics. It
will not receive any traffic nor will it send any health-checks or logs. It
is possible to disable many instances at once by adding the "
disabled"
keyword in a "defaults" section.
Set a default server address
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<address> is the IPv4 address of the default server. Alternatively, a
resolvable hostname is supported, but this name will be resolved
during start-up.
<ports> is a mandatory port specification. All connections will be sent
to this port, and it is not permitted to use port offsets as is
possible with normal servers.
The "
dispatch" keyword designates a default server for use when no other
server can take the connection. In the past it was used to forward non
persistent connections to an auxiliary load balancer. Due to its simple
syntax, it has also been used for simple TCP relays. It is recommended not to
use it for more clarity, and to use the "
server" directive instead.
Set the dynamic cookie secret key for a backend.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : The secret key to be used.
When dynamic cookies are enabled (see the "dynamic" directive for cookie),
a dynamic cookie is created for each server (unless one is explicitly
specified on the "
server" line), using a hash of the IP address of the
server, the TCP port, and the secret key.
That way, we can ensure session persistence across multiple load-balancers,
even if servers are dynamically added or removed.
Enable a proxy, frontend or backend.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
The "
enabled" keyword is used to explicitly enable an instance, when the
defaults has been set to "
disabled". This is very rarely used.
Return a file contents instead of errors generated by HAProxy
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 200, 400, 401, 403, 404, 405, 407, 408, 410,
413, 425, 429, 500, 501, 502, 503, and 504.
<file> designates a file containing the full HTTP response. It is
recommended to follow the common practice of appending ".http" to
the filename so that people do not confuse the response with HTML
error pages, and to use absolute paths, since files are read
before any chroot is performed.
It is important to understand that this keyword is not meant to rewrite
errors returned by the server, but errors detected and returned by HAProxy.
This is why the list of supported errors is limited to a small set.
Code 200 is emitted in response to requests matching a "
monitor-uri" rule.
The files are parsed when HAProxy starts and must be valid according to the
HTTP specification. They should not exceed the configured buffer size
(BUFSIZE), which generally is 16 kB, otherwise an internal error will be
returned. It is also wise not to put any reference to local contents
(e.g. images) in order to avoid loops between the client and HAProxy when all
servers are down, causing an error to be returned instead of an
image. Finally, The response cannot exceed (tune.bufsize - tune.maxrewrite)
so that "
http-after-response" rules still have room to operate (see
"
tune.maxrewrite").
The files are read at the same time as the configuration and kept in memory.
For this reason, the errors continue to be returned even when the process is
chrooted, and no file change is considered while the process is running. A
simple method for developing those files consists in associating them to the
403 status code and interrogating a blocked URL.
Example :
errorfile 400 /etc/haproxy/errorfiles/400badreq.http
errorfile 408 /dev/null
errorfile 403 /etc/haproxy/errorfiles/403forbid.http
errorfile 503 /etc/haproxy/errorfiles/503sorry.http
Import, fully or partially, the error files defined in the <name> http-errors
section.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the name of an existing http-errors section.
<code> is a HTTP status code. Several status code may be listed.
Currently, HAProxy is capable of generating codes 200, 400, 401,
403, 404, 405, 407, 408, 410, 413, 425, 429, 500, 501, 502, 503,
and 504.
Errors defined in the http-errors section with the name <name> are imported
in the current proxy. If no status code is specified, all error files of the
http-errors section are imported. Otherwise, only error files associated to
the listed status code are imported. Those error files override the already
defined custom errors for the proxy. And they may be overridden by following
ones. Functionally, it is exactly the same as declaring all error files by
hand using "
errorfile" directives.
Example :
errorfiles generic
errorfiles site-1 403 404
Return an HTTP redirection to a URL instead of errors generated by HAProxy
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 200, 400, 401, 403, 404, 405, 407, 408, 410,
413, 425, 429, 500, 501, 502, 503, and 504.
<url> it is the exact contents of the "Location" header. It may contain
either a relative URI to an error page hosted on the same site,
or an absolute URI designating an error page on another site.
Special care should be given to relative URIs to avoid redirect
loops if the URI itself may generate the same error (e.g. 500).
It is important to understand that this keyword is not meant to rewrite
errors returned by the server, but errors detected and returned by HAProxy.
This is why the list of supported errors is limited to a small set.
Code 200 is emitted in response to requests matching a "
monitor-uri" rule.
Note that both keyword return the HTTP 302 status code, which tells the
client to fetch the designated URL using the same HTTP method. This can be
quite problematic in case of non-GET methods such as POST, because the URL
sent to the client might not be allowed for something other than GET. To
work around this problem, please use "
errorloc303" which send the HTTP 303
status code, indicating to the client that the URL must be fetched with a GET
request.
Return an HTTP redirection to a URL instead of errors generated by HAProxy
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 200, 400, 401, 403, 404, 405, 407, 408, 410,
413, 425, 429, 500, 501, 502, 503, and 504.
<url> it is the exact contents of the "Location" header. It may contain
either a relative URI to an error page hosted on the same site,
or an absolute URI designating an error page on another site.
Special care should be given to relative URIs to avoid redirect
loops if the URI itself may generate the same error (e.g. 500).
It is important to understand that this keyword is not meant to rewrite
errors returned by the server, but errors detected and returned by HAProxy.
This is why the list of supported errors is limited to a small set.
Code 200 is emitted in response to requests matching a "
monitor-uri" rule.
Note that both keyword return the HTTP 303 status code, which tells the
client to fetch the designated URL using the same HTTP GET method. This
solves the usual problems associated with "
errorloc" and the 302 code. It is
possible that some very old browsers designed before HTTP/1.1 do not support
it, but no such problem has been reported till now.
Declare the from email address to be used in both the envelope and header
of email alerts. This is the address that email alerts are sent from.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<emailaddr> is the from email address to use when sending email alerts
Also requires "
email-alert mailers" and "
email-alert to" to be set
and if so sending email alerts is enabled for the proxy.
Declare the maximum log level of messages for which email alerts will be
sent. This acts as a filter on the sending of email alerts.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<level> One of the 8 syslog levels:
emerg alert crit err warning notice info debug
The above syslog levels are ordered from lowest to highest.
By default level is alert
Also requires "
email-alert from", "
email-alert mailers" and
"
email-alert to" to be set and if so sending email alerts is enabled
for the proxy.
Alerts are sent when :
* An un-paused server is marked as down and <level> is alert or lower
* A paused server is marked as down and <level> is notice or lower
* A server is marked as up or enters the drain state and <level>
is notice or lower
* "
option log-health-checks" is enabled, <level> is info or lower,
and a health check status update occurs
Declare the mailers to be used when sending email alerts
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<mailersect> is the name of the mailers section to send email alerts.
Also requires "
email-alert from" and "
email-alert to" to be set
and if so sending email alerts is enabled for the proxy.
Declare the to hostname address to be used when communicating with
mailers.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<hostname> is the hostname to use when communicating with mailers
By default the systems hostname is used.
Also requires "
email-alert from", "
email-alert mailers" and
"
email-alert to" to be set and if so sending email alerts is enabled
for the proxy.
Declare both the recipient address in the envelope and to address in the
header of email alerts. This is the address that email alerts are sent to.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<emailaddr> is the to email address to use when sending email alerts
Also requires "
email-alert mailers" and "
email-alert to" to be set
and if so sending email alerts is enabled for the proxy.
Specifies the log format string to use in case of connection error on the frontend side.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
This directive specifies the log format string that will be used for logs
containing information related to errors, timeouts, retries redispatches or
HTTP status code 5xx. This format will in short be used for every log line
that would be concerned by the "
log-separate-errors" option, including
connection errors described in
section 8.2.5.
If the directive is used in a defaults section, all subsequent frontends will
use the same log format. Please see
section 8.2.6 which covers the custom log
format string in depth.
"
error-log-format" directive overrides previous "
error-log-format"
directives.
Declare a condition to force persistence on down servers
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
By default, requests are not dispatched to down servers. It is possible to
force this using "
option persist", but it is unconditional and redispatches
to a valid server if "
option redispatch" is set. That leaves with very little
possibilities to force some requests to reach a server which is artificially
marked down for maintenance operations.
The "
force-persist" statement allows one to declare various ACL-based
conditions which, when met, will cause a request to ignore the down status of
a server and still try to connect to it. That makes it possible to start a
server, still replying an error to the health checks, and run a specially
configured browser to test the service. Among the handy methods, one could
use a specific source IP address, or a specific cookie. The cookie also has
the advantage that it can easily be added/removed on the browser from a test
page. Once the service is validated, it is then possible to open the service
to the world by returning a valid response to health checks.
The forced persistence is enabled when an "if" condition is met, or unless an
"unless" condition is met. The final redispatch is always disabled when this
is used.
Add the filter <name> in the filter list attached to the proxy.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the name of the filter. Officially supported filters are
referenced in section 9.
<param*> is a list of parameters accepted by the filter <name>. The
parsing of these parameters are the responsibility of the
filter. Please refer to the documentation of the corresponding
filter (section 9) for all details on the supported parameters.
Multiple occurrences of the filter line can be used for the same proxy. The
same filter can be referenced many times if needed.
Example:
listen
bind *:80
filter trace name BEFORE-HTTP-COMP
filter compression
filter trace name AFTER-HTTP-COMP
compression algo gzip
compression offload
server srv1 192.168.0.1:80
Specify at what backend load the servers will reach their maxconn
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<conns> is the number of connections on the backend which will make the
servers use the maximal number of connections.
When a server has a "
maxconn" parameter specified, it means that its number
of concurrent connections will never go higher. Additionally, if it has a
"
minconn" parameter, it indicates a dynamic limit following the backend's
load. The server will then always accept at least <minconn> connections,
never more than <maxconn>, and the limit will be on the ramp between both
values when the backend has less than <conns> concurrent connections. This
makes it possible to limit the load on the servers during normal loads, but
push it further for important loads without overloading the servers during
exceptional loads.
Since it's hard to get this value right, HAProxy automatically sets it to
10% of the sum of the maxconns of all frontends that may branch to this
backend (based on "
use_backend" and "
default_backend" rules). That way it's
safe to leave it unset. However, "
use_backend" involving dynamic names are
not counted since there is no way to know if they could match or not.
Example :
backend dynamic
fullconn 10000
server srv1 dyn1:80 minconn 100 maxconn 1000
server srv2 dyn2:80 minconn 100 maxconn 1000
Specify the balancing factor for bounded-load consistent hashing
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<factor> is the control for the maximum number of concurrent requests to
send to a server, expressed as a percentage of the average number
of concurrent requests across all of the active servers.
Specifying a "
hash-balance-factor" for a server with "hash-type consistent"
enables an algorithm that prevents any one server from getting too many
requests at once, even if some hash buckets receive many more requests than
others. Setting <factor> to 0 (the default) disables the feature. Otherwise,
<factor> is a percentage greater than 100. For example, if <factor> is 150,
then no server will be allowed to have a load more than 1.5 times the average.
If server weights are used, they will be respected.
If the first-choice server is disqualified, the algorithm will choose another
server based on the request hash, until a server with additional capacity is
found. A higher <factor> allows more imbalance between the servers, while a
lower <factor> means that more servers will be checked on average, affecting
performance. Reasonable values are from 125 to 200.
This setting is also used by "balance random" which internally relies on the
consistent hashing mechanism.
Specify a method to use for mapping hashes to servers
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<method> is the method used to select a server from the hash computed by
the <function> :
map-based the hash table is a static array containing all alive servers.
The hashes will be very smooth, will consider weights, but
will be static in that weight changes while a server is up
will be ignored. This means that there will be no slow start.
Also, since a server is selected by its position in the array,
most mappings are changed when the server count changes. This
means that when a server goes up or down, or when a server is
added to a farm, most connections will be redistributed to
different servers. This can be inconvenient with caches for
instance.
consistent the hash table is a tree filled with many occurrences of each
server. The hash key is looked up in the tree and the closest
server is chosen. This hash is dynamic, it supports changing
weights while the servers are up, so it is compatible with the
slow start feature. It has the advantage that when a server
goes up or down, only its associations are moved. When a
server is added to the farm, only a few part of the mappings
are redistributed, making it an ideal method for caches.
However, due to its principle, the distribution will never be
very smooth and it may sometimes be necessary to adjust a
server's weight or its ID to get a more balanced distribution.
In order to get the same distribution on multiple load
balancers, it is important that all servers have the exact
same IDs. Note: consistent hash uses sdbm and avalanche if no
hash function is specified.
<function> is the hash function to be used :
sdbm this function was created initially for sdbm (a public-domain
reimplementation of ndbm) database library. It was found to do
well in scrambling bits, causing better distribution of the keys
and fewer splits. It also happens to be a good general hashing
function with good distribution, unless the total server weight
is a multiple of 64, in which case applying the avalanche
modifier may help.
djb2 this function was first proposed by Dan Bernstein many years ago
on comp.lang.c. Studies have shown that for certain workload this
function provides a better distribution than sdbm. It generally
works well with text-based inputs though it can perform extremely
poorly with numeric-only input or when the total server weight is
a multiple of 33, unless the avalanche modifier is also used.
wt6 this function was designed for HAProxy while testing other
functions in the past. It is not as smooth as the other ones, but
is much less sensible to the input data set or to the number of
servers. It can make sense as an alternative to sdbm+avalanche or
djb2+avalanche for consistent hashing or when hashing on numeric
data such as a source IP address or a visitor identifier in a URL
parameter.
crc32 this is the most common CRC32 implementation as used in Ethernet,
gzip, PNG, etc. It is slower than the other ones but may provide
a better distribution or less predictable results especially when
used on strings.
none don't hash the key, the key will be used as a hash, this can be
useful to manually hash the key using a converter for that purpose
and let haproxy use the result directly.
<modifier> indicates an optional method applied after hashing the key :
avalanche This directive indicates that the result from the hash
function above should not be used in its raw form but that
a 4-byte full avalanche hash must be applied first. The
purpose of this step is to mix the resulting bits from the
previous hash in order to avoid any undesired effect when
the input contains some limited values or when the number of
servers is a multiple of one of the hash's components (64
for SDBM, 33 for DJB2). Enabling avalanche tends to make the
result less predictable, but it's also not as smooth as when
using the original function. Some testing might be needed
with some workloads. This hash is one of the many proposed
by Bob Jenkins.
The default hash type is "map-based" and is recommended for most usages. The
default function is "
sdbm", the selection of a function should be based on
the range of the values being hashed.
Access control for all Layer 7 responses (server, applet/service and internal
ones).
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
The http-after-response statement defines a set of rules which apply to layer
7 processing. The rules are evaluated in their declaration order when they
are met in a frontend, listen or backend section. Since these rules apply on
responses, the backend rules are applied first, followed by the frontend's
rules. Any rule may optionally be followed by an ACL-based condition, in
which case it will only be evaluated if the condition evaluates true.
Unlike http-response rules, these ones are applied on all responses, the
server ones but also to all responses generated by HAProxy. These rules are
evaluated at the end of the responses analysis, before the data forwarding
phase.
The condition is evaluated just before the action is executed, and the action
is performed exactly once. As such, there is no problem if an action changes
an element which is checked as part of the condition. This also means that
multiple actions may rely on the same condition so that the first action that
changes the condition's evaluation is sufficient to implicitly disable the
remaining actions. This is used for example when trying to assign a value to
a variable from various sources when it's empty. There is no limit to the
number of "
http-after-response" statements per instance.
The first keyword after "
http-after-response" in the syntax is the rule's
action, optionally followed by a varying number of arguments for the action.
The supported actions and their respective syntaxes are enumerated in section
4.3 "Actions" (look for actions which tick "HTTP Aft").
This directive is only available from named defaults sections, not anonymous
ones. Rules defined in the defaults section are evaluated before ones in the
associated proxy section. To avoid ambiguities, in this case the same
defaults section cannot be used by proxies with the frontend capability and
by proxies with the backend capability. It means a listen section cannot use
a defaults section defining such rules.
Note: Errors emitted in early stage of the request parsing are handled by the
multiplexer at a lower level, before any http analysis. Thus no
http-after-response ruleset is evaluated on these errors.
Example:
http-after-response set-header Strict-Transport-Security "max-age=31536000"
http-after-response set-header Cache-Control "no-store,no-cache,private"
http-after-response set-header Pragma "no-cache"
Defines a comment for the following the http-check rule, reported in logs if
it fails.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<string> is the comment message to add in logs if the following http-check
rule fails.
It only works for connect, send and expect rules. It is useful to make
user-friendly error reporting.
http-check connect [default] [port <expr>] [addr <ip>] [send-proxy]
[via-socks4] [ssl] [sni <sni>] [alpn <alpn>] [linger]
[proto <name>] [comment <msg>] Opens a new connection to perform an HTTP health check
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
default Use default options of the server line to do the health
checks. The server options are used only if not redefined.
port <expr> if not set, check port or server port is used.
It tells HAProxy where to open the connection to.
<port> must be a valid TCP port source integer, from 1 to
65535 or an sample-fetch expression.
addr <ip> defines the IP address to do the health check.
send-proxy send a PROXY protocol string
via-socks4 enables outgoing health checks using upstream socks4 proxy.
ssl opens a ciphered connection
sni <sni> specifies the SNI to use to do health checks over SSL.
alpn <alpn> defines which protocols to advertise with ALPN. The protocol
list consists in a comma-delimited list of protocol names,
for instance: "h2,http/1.1". If it is not set, the server ALPN
is used.
proto <name> forces the multiplexer's protocol to use for this connection.
It must be an HTTP mux protocol and it must be usable on the
backend side. The list of available protocols is reported in
haproxy -vv.
linger cleanly close the connection instead of using a single RST.
Just like tcp-check health checks, it is possible to configure the connection
to use to perform HTTP health check. This directive should also be used to
describe a scenario involving several request/response exchanges, possibly on
different ports or with different servers.
When there are no TCP port configured on the server line neither server port
directive, then the first step of the http-check sequence must be to specify
the port with a "
http-check connect".
In an http-check ruleset a 'connect' is required, it is also mandatory to start
the ruleset with a 'connect' rule. Purpose is to ensure admin know what they
do.
When a connect must start the ruleset, if may still be preceded by set-var,
unset-var or comment rules.
Examples :
option httpchk
http-check connect
http-check send meth GET uri / ver HTTP/1.1 hdr host haproxy.1wt.eu
http-check expect status 200-399
http-check connect port 443 ssl sni haproxy.1wt.eu
http-check send meth GET uri / ver HTTP/1.1 hdr host haproxy.1wt.eu
http-check expect status 200-399
server www 10.0.0.1 check port 80
Enable a maintenance mode upon HTTP/404 response to health-checks
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When this option is set, a server which returns an HTTP code 404 will be
excluded from further load-balancing, but will still receive persistent
connections. This provides a very convenient method for Web administrators
to perform a graceful shutdown of their servers. It is also important to note
that a server which is detected as failed while it was in this mode will not
generate an alert, just a notice. If the server responds 2xx or 3xx again, it
will immediately be reinserted into the farm. The status on the stats page
reports "NOLB" for a server in this mode. It is important to note that this
option only works in conjunction with the "
httpchk" option. If this option
is used with "
http-check expect", then it has precedence over it so that 404
responses will still be considered as soft-stop. Note also that a stopped
server will stay stopped even if it replies 404s. This option is only
evaluated for running servers.
http-check expect [min-recv <int>] [comment <msg>]
[ok-status <st>] [error-status <st>] [tout-status <st>]
[on-success <fmt>] [on-error <fmt>] [status-code <expr>]
[!] <match> <pattern> Make HTTP health checks consider response contents or specific status codes
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
min-recv is optional and can define the minimum amount of data required to
evaluate the current expect rule. If the number of received bytes
is under this limit, the check will wait for more data. This
option can be used to resolve some ambiguous matching rules or to
avoid executing costly regex matches on content known to be still
incomplete. If an exact string is used, the minimum between the
string length and this parameter is used. This parameter is
ignored if it is set to -1. If the expect rule does not match,
the check will wait for more data. If set to 0, the evaluation
result is always conclusive.
ok-status <st> is optional and can be used to set the check status if
the expect rule is successfully evaluated and if it is
the last rule in the tcp-check ruleset. "L7OK", "L7OKC",
"L6OK" and "L4OK" are supported :
- L7OK : check passed on layer 7
- L7OKC : check conditionally passed on layer 7, set
server to NOLB state.
- L6OK : check passed on layer 6
- L4OK : check passed on layer 4
By default "L7OK" is used.
error-status <st> is optional and can be used to set the check status if
an error occurred during the expect rule evaluation.
"L7OKC", "L7RSP", "L7STS", "L6RSP" and "L4CON" are
supported :
- L7OKC : check conditionally passed on layer 7, set
server to NOLB state.
- L7RSP : layer 7 invalid response - protocol error
- L7STS : layer 7 response error, for example HTTP 5xx
- L6RSP : layer 6 invalid response - protocol error
- L4CON : layer 1-4 connection problem
By default "L7RSP" is used.
tout-status <st> is optional and can be used to set the check status if
a timeout occurred during the expect rule evaluation.
"L7TOUT", "L6TOUT", and "L4TOUT" are supported :
- L7TOUT : layer 7 (HTTP/SMTP) timeout
- L6TOUT : layer 6 (SSL) timeout
- L4TOUT : layer 1-4 timeout
By default "L7TOUT" is used.
on-success <fmt> is optional and can be used to customize the
informational message reported in logs if the expect
rule is successfully evaluated and if it is the last rule
in the tcp-check ruleset. <fmt> is a log-format string.
on-error <fmt> is optional and can be used to customize the
informational message reported in logs if an error
occurred during the expect rule evaluation. <fmt> is a
log-format string.
<match> is a keyword indicating how to look for a specific pattern in the
response. The keyword may be one of "status", "rstatus", "hdr",
"fhdr", "string", or "rstring". The keyword may be preceded by an
exclamation mark ("!") to negate the match. Spaces are allowed
between the exclamation mark and the keyword. See below for more
details on the supported keywords.
<pattern> is the pattern to look for. It may be a string, a regular
expression or a more complex pattern with several arguments. If
the string pattern contains spaces, they must be escaped with the
usual backslash ('\').
By default, "
option httpchk" considers that response statuses 2xx and 3xx
are valid, and that others are invalid. When "
http-check expect" is used,
it defines what is considered valid or invalid. Only one "
http-check"
statement is supported in a backend. If a server fails to respond or times
out, the check obviously fails. The available matches are :
status <codes> : test the status codes found parsing <codes> string. it
must be a comma-separated list of status codes or range
codes. A health check response will be considered as
valid if the response's status code matches any status
code or is inside any range of the list. If the "
status"
keyword is prefixed with "!", then the response will be
considered invalid if the status code matches.
rstatus <regex> : test a regular expression for the HTTP status code.
A health check response will be considered valid if the
response's status code matches the expression. If the
"rstatus" keyword is prefixed with "!", then the response
will be considered invalid if the status code matches.
This is mostly used to check for multiple codes.
hdr { name | name-lf } [ -m <meth> ] <name>
[ { value | value-lf } [ -m <meth> ] <value> :
test the specified header pattern on the HTTP response
headers. The name pattern is mandatory but the value
pattern is optional. If not specified, only the header
presence is verified. <meth> is the matching method,
applied on the header name or the header value. Supported
matching methods are "
str" (exact match), "beg" (prefix
match), "end" (suffix match), "
sub" (substring match) or
"reg" (regex match). If not specified, exact matching
method is used. If the "name-lf" parameter is used,
<name> is evaluated as a log-format string. If "value-lf"
parameter is used, <value> is evaluated as a log-format
string. These parameters cannot be used with the regex
matching method. Finally, the header value is considered
as comma-separated list. Note that matchings are case
insensitive on the header names.
fhdr { name | name-lf } [ -m <meth> ] <name>
[ { value | value-lf } [ -m <meth> ] <value> :
test the specified full header pattern on the HTTP
response headers. It does exactly the same than "
hdr"
keyword, except the full header value is tested, commas
are not considered as delimiters.
string <string> : test the exact string match in the HTTP response body.
A health check response will be considered valid if the
response's body contains this exact string. If the
"string" keyword is prefixed with "!", then the response
will be considered invalid if the body contains this
string. This can be used to look for a mandatory word at
the end of a dynamic page, or to detect a failure when a
specific error appears on the check page (e.g. a stack
trace).
rstring <regex> : test a regular expression on the HTTP response body.
A health check response will be considered valid if the
response's body matches this expression. If the "rstring"
keyword is prefixed with "!", then the response will be
considered invalid if the body matches the expression.
This can be used to look for a mandatory word at the end
of a dynamic page, or to detect a failure when a specific
error appears on the check page (e.g. a stack trace).
string-lf <fmt> : test a log-format string match in the HTTP response body.
A health check response will be considered valid if the
response's body contains the string resulting of the
evaluation of <fmt>, which follows the log-format rules.
If prefixed with "!", then the response will be
considered invalid if the body contains the string.
It is important to note that the responses will be limited to a certain size
defined by the global "
tune.bufsize" option, which defaults to 16384 bytes.
Thus, too large responses may not contain the mandatory pattern when using
"string" or "rstring". If a large response is absolutely required, it is
possible to change the default max size by setting the global variable.
However, it is worth keeping in mind that parsing very large responses can
waste some CPU cycles, especially when regular expressions are used, and that
it is always better to focus the checks on smaller resources.
In an http-check ruleset, the last expect rule may be implicit. If no expect
rule is specified after the last "
http-check send", an implicit expect rule
is defined to match on 2xx or 3xx status codes. It means this rule is also
defined if there is no "
http-check" rule at all, when only "
option httpchk"
is set.
Last, if "
http-check expect" is combined with "
http-check disable-on-404",
then this last one has precedence when the server responds with 404.
Examples :
http-check expect status 200,201,300-310
http-check expect header name "set-cookie" value -m beg "sessid="
http-check expect ! string SQL\ Error
http-check expect ! rstatus ^5
http-check expect rstring <!--tag:[0-9a-f]*--></html>
http-check send [meth <method>] [{ uri <uri> | uri-lf <fmt> }>]
[ver <version>]
[hdr <name> <fmt>]*
[{ body <string> | body-lf <fmt> }]
[comment <msg>] Add a possible list of headers and/or a body to the request sent during HTTP
health checks.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
meth <method> is the optional HTTP method used with the requests. When not
set, the "OPTIONS" method is used, as it generally requires
low server processing and is easy to filter out from the
logs. Any method may be used, though it is not recommended
to invent non-standard ones.
uri <uri> is optional and set the URI referenced in the HTTP requests
to the string <uri>. It defaults to "/" which is accessible
by default on almost any server, but may be changed to any
other URI. Query strings are permitted.
uri-lf <fmt> is optional and set the URI referenced in the HTTP requests
using the log-format string <fmt>. It defaults to "/" which
is accessible by default on almost any server, but may be
changed to any other URI. Query strings are permitted.
ver <version> is the optional HTTP version string. It defaults to
"HTTP/1.0" but some servers might behave incorrectly in HTTP
1.0, so turning it to HTTP/1.1 may sometimes help. Note that
the Host field is mandatory in HTTP/1.1, use "hdr" argument
to add it.
hdr <name> <fmt> adds the HTTP header field whose name is specified in
<name> and whose value is defined by <fmt>, which follows
to the log-format rules.
body <string> add the body defined by <string> to the request sent during
HTTP health checks. If defined, the "Content-Length" header
is thus automatically added to the request.
body-lf <fmt> add the body defined by the log-format string <fmt> to the
request sent during HTTP health checks. If defined, the
"Content-Length" header is thus automatically added to the
request.
In addition to the request line defined by the "
option httpchk" directive,
this one is the valid way to add some headers and optionally a body to the
request sent during HTTP health checks. If a body is defined, the associate
"Content-Length" header is automatically added. Thus, this header or
"Transfer-encoding" header should not be present in the request provided by
"
http-check send". If so, it will be ignored. The old trick consisting to add
headers after the version string on the "
option httpchk" line is now
deprecated.
Also "
http-check send" doesn't support HTTP keep-alive. Keep in mind that it
will automatically append a "Connection: close" header, unless a Connection
header has already already been configured via a hdr entry.
Note that the Host header and the request authority, when both defined, are
automatically synchronized. It means when the HTTP request is sent, when a
Host is inserted in the request, the request authority is accordingly
updated. Thus, don't be surprised if the Host header value overwrites the
configured request authority.
Note also for now, no Host header is automatically added in HTTP/1.1 or above
requests. You should add it explicitly.
Enable emission of a state header with HTTP health checks
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When this option is set, HAProxy will systematically send a special header
"X-Haproxy-Server-State" with a list of parameters indicating to each server
how they are seen by HAProxy. This can be used for instance when a server is
manipulated without access to HAProxy and the operator needs to know whether
HAProxy still sees it up or not, or if the server is the last one in a farm.
The header is composed of fields delimited by semi-colons, the first of which
is a word ("UP", "DOWN", "NOLB"), possibly followed by a number of valid
checks on the total number before transition, just as appears in the stats
interface. Next headers are in the form "<variable>=<value>", indicating in
no specific order some values available in the stats interface :
- a variable "address", containing the address of the backend server.
This corresponds to the <address> field in the server declaration. For
unix domain sockets, it will read "unix".
- a variable "
port", containing the port of the backend server. This
corresponds to the <port> field in the server declaration. For unix
domain sockets, it will read "unix".
- a variable "
name", containing the name of the backend followed by a slash
("/") then the name of the server. This can be used when a server is
checked in multiple backends.
- a variable "
node" containing the name of the HAProxy node, as set in the
global "
node" variable, otherwise the system's hostname if unspecified.
- a variable "
weight" indicating the weight of the server, a slash ("/")
and the total weight of the farm (just counting usable servers). This
helps to know if other servers are available to handle the load when this
one fails.
- a variable "scur" indicating the current number of concurrent connections
on the server, followed by a slash ("/") then the total number of
connections on all servers of the same backend.
- a variable "qcur" indicating the current number of requests in the
server's queue.
Example of a header received by the application server :
>>> X-Haproxy-Server-State: UP 2/3; name=bck/srv2; node=lb1; weight=1/2; \
scur=13/22; qcur=0
This operation sets the content of a variable. The variable is declared inline.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<var-name> The name of the variable starts with an indication about its
scope. The scopes allowed for http-check are:
"proc" : the variable is shared with the whole process.
"sess" : the variable is shared with the tcp-check session.
"check": the variable is declared for the lifetime of the tcp-check.
This prefix is followed by a name. The separator is a '.'.
The name may only contain characters 'a-z', 'A-Z', '0-9', '.',
and '-'.
<cond> A set of conditions that must all be true for the variable to
actually be set (such as "ifnotempty", "ifgt" ...). See the
set-var converter's description for a full list of possible
conditions.
<expr> Is a sample-fetch expression potentially followed by converters.
<fmt> This is the value expressed using log-format rules (see Custom
Log Format in section 8.2.6).
Examples :
http-check set-var(check.port) int(1234)
http-check set-var-fmt(check.port) "name=%H"
Free a reference to a variable within its scope.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<var-name> The name of the variable starts with an indication about its
scope. The scopes allowed for http-check are:
"proc" : the variable is shared with the whole process.
"sess" : the variable is shared with the tcp-check session.
"check": the variable is declared for the lifetime of the tcp-check.
This prefix is followed by a name. The separator is a '.'.
The name may only contain characters 'a-z', 'A-Z', '0-9', '.',
and '-'.
Examples :
http-check unset-var(check.port)
http-error status <code> [content-type <type>]
[ { default-errorfiles | errorfile <file> | errorfiles <name> |
file <file> | lf-file <file> | string <str> | lf-string <fmt> } ]
[ hdr <name> <fmt> ]*
Defines a custom error message to use instead of errors generated by HAProxy.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :status <code> is the HTTP status code. It must be specified.
Currently, HAProxy is capable of generating codes
200, 400, 401, 403, 404, 405, 407, 408, 410, 413, 425,
429, 500, 501, 502, 503, and 504.
content-type <type> is the response content type, for instance
"text/plain". This parameter is ignored and should be
omitted when an errorfile is configured or when the
payload is empty. Otherwise, it must be defined.
default-errorfiles Reset the previously defined error message for current
proxy for the status <code>. If used on a backend, the
frontend error message is used, if defined. If used on
a frontend, the default error message is used.
errorfile <file> designates a file containing the full HTTP response.
It is recommended to follow the common practice of
appending ".http" to the filename so that people do
not confuse the response with HTML error pages, and to
use absolute paths, since files are read before any
chroot is performed.
errorfiles <name> designates the http-errors section to use to import
the error message with the status code <code>. If no
such message is found, the proxy's error messages are
considered.
file <file> specifies the file to use as response payload. If the
file is not empty, its content-type must be set as
argument to "content-type", otherwise, any
"content-type" argument is ignored. <file> is
considered as a raw string.
string <str> specifies the raw string to use as response payload.
The content-type must always be set as argument to
"content-type".
lf-file <file> specifies the file to use as response payload. If the
file is not empty, its content-type must be set as
argument to "content-type", otherwise, any
"content-type" argument is ignored. <file> is
evaluated as a log-format string.
lf-string <str> specifies the log-format string to use as response
payload. The content-type must always be set as
argument to "content-type".
hdr <name> <fmt> adds to the response the HTTP header field whose name
is specified in <name> and whose value is defined by
<fmt>, which follows to the log-format rules.
This parameter is ignored if an errorfile is used.
This directive may be used instead of "
errorfile", to define a custom error
message. As "
errorfile" directive, it is used for errors detected and
returned by HAProxy. If an errorfile is defined, it is parsed when HAProxy
starts and must be valid according to the HTTP standards. The generated
response must not exceed the configured buffer size (BUFFSIZE), otherwise an
internal error will be returned. Finally, if you consider to use some
http-after-response rules to rewrite these errors, the reserved buffer space
should be available (see "
tune.maxrewrite").
The files are read at the same time as the configuration and kept in memory.
For this reason, the errors continue to be returned even when the process is
chrooted, and no file change is considered while the process is running.
Note: 400/408/500 errors emitted in early stage of the request parsing are
handled by the multiplexer at a lower level. No custom formatting is
supported at this level. Thus only static error messages, defined with
"
errorfile" directive, are supported. However, this limitation only
exists during the request headers parsing or between two transactions.
http-request <action> [options...] [ { if | unless } <condition> ] Access control for Layer 7 requests
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
The http-request statement defines a set of rules which apply to layer 7
processing. The rules are evaluated in their declaration order when they are
met in a frontend, listen or backend section. Any rule may optionally be
followed by an ACL-based condition, in which case it will only be evaluated
if the condition evaluates to true.
The condition is evaluated just before the action is executed, and the action
is performed exactly once. As such, there is no problem if an action changes
an element which is checked as part of the condition. This also means that
multiple actions may rely on the same condition so that the first action that
changes the condition's evaluation is sufficient to implicitly disable the
remaining actions. This is used for example when trying to assign a value to
a variable from various sources when it's empty. There is no limit to the
number of "
http-request" statements per instance.
The first keyword after "
http-request" in the syntax is the rule's action,
optionally followed by a varying number of arguments for the action. The
supported actions and their respective syntaxes are enumerated in
section 4.3
"Actions" (look for actions which tick "HTTP Req").
This directive is only available from named defaults sections, not anonymous
ones. Rules defined in the defaults section are evaluated before ones in the
associated proxy section. To avoid ambiguities, in this case the same
defaults section cannot be used by proxies with the frontend capability and
by proxies with the backend capability. It means a listen section cannot use
a defaults section defining such rules.
Example:
acl nagios src 192.168.129.3
acl local_net src 192.168.0.0/16
acl auth_ok http_auth(L1)
http-request allow if nagios
http-request allow if local_net auth_ok
http-request auth realm Gimme if local_net auth_ok
http-request deny
Example:
acl key req.hdr(X-Add-Acl-Key) -m found
acl add path /addacl
acl del path /delacl
acl myhost hdr(Host) -f myhost.lst
http-request add-acl(myhost.lst) %[req.hdr(X-Add-Acl-Key)] if key add
http-request del-acl(myhost.lst) %[req.hdr(X-Add-Acl-Key)] if key del
Example:
acl value req.hdr(X-Value) -m found
acl setmap path /setmap
acl delmap path /delmap
use_backend bk_appli if { hdr(Host),map_str(map.lst) -m found }
http-request set-map(map.lst) %[src] %[req.hdr(X-Value)] if setmap value
http-request del-map(map.lst) %[src] if delmap
http-response <action> <options...> [ { if | unless } <condition> ] Access control for Layer 7 responses
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
The http-response statement defines a set of rules which apply to layer 7
processing. The rules are evaluated in their declaration order when they are
met in a frontend, listen or backend section. Since these rules apply on
responses, the backend rules are applied first, followed by the frontend's
rules. Any rule may optionally be followed by an ACL-based condition, in
which case it will only be evaluated if the condition evaluates to true.
The condition is evaluated just before the action is executed, and the action
is performed exactly once. As such, there is no problem if an action changes
an element which is checked as part of the condition. This also means that
multiple actions may rely on the same condition so that the first action that
changes the condition's evaluation is sufficient to implicitly disable the
remaining actions. This is used for example when trying to assign a value to
a variable from various sources when it's empty. There is no limit to the
number of "
http-response" statements per instance.
The first keyword after "
http-response" in the syntax is the rule's action,
optionally followed by a varying number of arguments for the action. The
supported actions and their respective syntaxes are enumerated in
section 4.3
"Actions" (look for actions which tick "HTTP Res").
This directive is only available from named defaults sections, not anonymous
ones. Rules defined in the defaults section are evaluated before ones in the
associated proxy section. To avoid ambiguities, in this case the same
defaults section cannot be used by proxies with the frontend capability and
by proxies with the backend capability. It means a listen section cannot use
a defaults section defining such rules.
Example:
acl key_acl res.hdr(X-Acl-Key) -m found
acl myhost hdr(Host) -f myhost.lst
http-response add-acl(myhost.lst) %[res.hdr(X-Acl-Key)] if key_acl
http-response del-acl(myhost.lst) %[res.hdr(X-Acl-Key)] if key_acl
Example:
acl value res.hdr(X-Value) -m found
use_backend bk_appli if { hdr(Host),map_str(map.lst) -m found }
http-response set-map(map.lst) %[src] %[res.hdr(X-Value)] if value
http-response del-map(map.lst) %[src] if ! value
Declare how idle HTTP connections may be shared between requests
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
By default, a connection established between HAProxy and the backend server
which is considered safe for reuse is moved back to the server's idle
connections pool so that any other request can make use of it. This is the
"safe" strategy below.
The argument indicates the desired connection reuse strategy :
- "never" : idle connections are never shared between sessions. This mode
may be enforced to cancel a different strategy inherited from
a defaults section or for troubleshooting. For example, if an
old bogus application considers that multiple requests over
the same connection come from the same client and it is not
possible to fix the application, it may be desirable to
disable connection sharing in a single backend. An example of
such an application could be an old HAProxy using cookie
insertion in tunnel mode and not checking any request past the
first one.
- "safe" : this is the default and the recommended strategy. The first
request of a session is always sent over its own connection,
and only subsequent requests may be dispatched over other
existing connections. This ensures that in case the server
closes the connection when the request is being sent, the
browser can decide to silently retry it. Since it is exactly
equivalent to regular keep-alive, there should be no side
effects. There is also a special handling for the connections
using protocols subject to Head-of-line blocking (backend with
h2 or fcgi). In this case, when at least one stream is
processed, the used connection is reserved to handle streams
of the same session. When no more streams are processed, the
connection is released and can be reused.
- "aggressive" : this mode may be useful in webservices environments where
all servers are not necessarily known and where it would be
appreciable to deliver most first requests over existing
connections. In this case, first requests are only delivered
over existing connections that have been reused at least once,
proving that the server correctly supports connection reuse.
It should only be used when it's sure that the client can
retry a failed request once in a while and where the benefit
of aggressive connection reuse significantly outweighs the
downsides of rare connection failures.
- "always" : this mode is only recommended when the path to the server is
known for never breaking existing connections quickly after
releasing them. It allows the first request of a session to be
sent to an existing connection. This can provide a significant
performance increase over the "safe" strategy when the backend
is a cache farm, since such components tend to show a
consistent behavior and will benefit from the connection
sharing. It is recommended that the "
http-keep-alive" timeout
remains low in this mode so that no dead connections remain
usable. In most cases, this will lead to the same performance
gains as "aggressive" but with more risks. It should only be
used when it improves the situation over "aggressive".
When http connection sharing is enabled, a great care is taken to respect the
connection properties and compatibility. Indeed, some properties are specific
and it is not possible to reuse it blindly. Those are the SSL SNI, source
and destination address, proxy protocol block as well as tos and mark
sockopts. A connection is reused only if it shares the same set of properties
with the request.
Also note that connections with certain bogus authentication schemes (relying
on the connection) like NTLM are marked private if possible and never shared.
This won't be the case however when using a protocol with multiplexing
abilities and using reuse mode level value greater than the default "safe"
strategy as in this case nothing prevents the connection from being already
shared.
A connection pool is involved and configurable with "
pool-max-conn".
Note: connection reuse improves the accuracy of the "server maxconn" setting,
because almost no new connection will be established while idle connections
remain available. This is particularly true with the "always" strategy.
The rules to decide to keep an idle connection opened or to close it after
processing are also governed by the "
tune.pool-low-fd-ratio" (default: 20%)
and "
tune.pool-high-fd-ratio" (default: 25%). These correspond to the
percentage of total file descriptors spent in idle connections above which
haproxy will respectively refrain from keeping a connection opened after a
response, and actively kill idle connections. Some setups using a very high
ratio of idle connections, either because of too low a global "
maxconn", or
due to a lot of HTTP/2 or HTTP/3 traffic on the frontend (few connections)
but HTTP/1 connections on the backend, may observe a lower reuse rate because
too few connections are kept open. It may be desirable in this case to adjust
such thresholds or simply to increase the global "
maxconn" value.
Similarly, when thread groups are explicitly enabled, it is important to
understand that idle connections are only usable between threads from a same
group. As such it may happen that unfair load between groups leads to more
idle connections being needed, causing a lower reuse rate. The same solution
may then be applied (increase global "
maxconn" or increase pool ratios).
Add the server name to a request. Use the header string given by <header>
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<header> The header string to use to send the server name
The "
http-send-name-header" statement causes the header field named <header>
to be set to the name of the target server at the moment the request is about
to be sent on the wire. Any existing occurrences of this header are removed.
Upon retries and redispatches, the header field is updated to always reflect
the server being attempted to connect to. Given that this header is modified
very late in the connection setup, it may have unexpected effects on already
modified headers. For example using it with transport-level header such as
connection, content-length, transfer-encoding and so on will likely result in
invalid requests being sent to the server. Additionally it has been reported
that this directive is currently being used as a way to overwrite the Host
header field in outgoing requests; while this trick has been known to work
as a side effect of the feature for some time, it is not officially supported
and might possibly not work anymore in a future version depending on the
technical difficulties this feature induces. A long-term solution instead
consists in fixing the application which required this trick so that it binds
to the correct host name.
Set a persistent ID to a proxy.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
Set a persistent ID for the proxy. This ID must be unique and positive.
An unused ID will automatically be assigned if unset. The first assigned
value will be 1. This ID is currently only returned in statistics.
Declare a condition to ignore persistence
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
By default, when cookie persistence is enabled, every requests containing
the cookie are unconditionally persistent (assuming the target server is up
and running).
The "
ignore-persist" statement allows one to declare various ACL-based
conditions which, when met, will cause a request to ignore persistence.
This is sometimes useful to load balance requests for static files, which
often don't require persistence. This can also be used to fully disable
persistence for a specific User-Agent (for example, some web crawler bots).
The persistence is ignored when an "if" condition is met, or unless an
"unless" condition is met.
Example:
acl url_static path_beg /static /images /img /css
acl url_static path_end .gif .png .jpg .css .js
ignore-persist if url_static
Allow seamless reload of HAProxy
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
This directive points HAProxy to a file where server state from previous
running process has been saved. That way, when starting up, before handling
traffic, the new process can apply old states to servers exactly has if no
reload occurred. The purpose of the "
load-server-state-from-file" directive is
to tell HAProxy which file to use. For now, only 2 arguments to either prevent
loading state or load states from a file containing all backends and servers.
The state file can be generated by running the command "show servers state"
over the stats socket and redirect output.
The format of the file is versioned and is very specific. To understand it,
please read the documentation of the "show servers state" command (chapter
9.3 of Management Guide).
Arguments:global load the content of the file pointed by the global directive
named "server-state-file".
local load the content of the file pointed by the directive
"server-state-file-name" if set. If not set, then the backend
name is used as a file name.
none don't load any stat for this backend
Notes:
- server's IP address is preserved across reloads by default, but the
order can be changed thanks to the server's "
init-addr" setting. This
means that an IP address change performed on the CLI at run time will
be preserved, and that any change to the local resolver (e.g. /etc/hosts)
will possibly not have any effect if the state file is in use.
- server's weight is applied from previous running process unless it has
has changed between previous and new configuration files.
Example:
Minimal configuration
global
stats socket /tmp/socket
server-state-file /tmp/server_state
defaults
load-server-state-from-file global
backend bk
server s1 127.0.0.1:22 check weight 11
server s2 127.0.0.1:22 check weight 12
Then one can run :
socat /tmp/socket - <<< "show servers state" > /tmp/server_state
Content of the file /tmp/server_state would be like this:
1
# <field names skipped for the doc example>
1 bk 1 s1 127.0.0.1 2 0 11 11 4 6 3 4 6 0 0
1 bk 2 s2 127.0.0.1 2 0 12 12 4 6 3 4 6 0 0
Example:
Minimal configuration
global
stats socket /tmp/socket
server-state-base /etc/haproxy/states
defaults
load-server-state-from-file local
backend bk
server s1 127.0.0.1:22 check weight 11
server s2 127.0.0.1:22 check weight 12
Then one can run :
socat /tmp/socket - <<< "show servers state bk" > /etc/haproxy/states/bk
Content of the file /etc/haproxy/states/bk would be like this:
1
# <field names skipped for the doc example>
1 bk 1 s1 127.0.0.1 2 0 11 11 4 6 3 4 6 0 0
1 bk 2 s2 127.0.0.1 2 0 12 12 4 6 3 4 6 0 0
log <target> [len <length>] [format <format>] [sample <ranges>:<sample_size>]
<facility> [<level> [<minlevel>]] Enable per-instance logging of events and traffic.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Prefix :
no should be used when the logger list must be flushed. For example,
if you don't want to inherit from the default logger list. This
prefix does not allow arguments.
Arguments :global should be used when the instance's logging parameters are the
same as the global ones. This is the most common usage. "global"
replaces <target>, <facility> and <level> with those of the log
entries found in the "global" section. Only one "log global"
statement may be used per instance, and this form takes no other
parameter.
<target> indicates where to send the logs. It takes the same format as
for the "global" section's logs, and can be one of :
- An IPv4 address optionally followed by a colon (':') and a UDP
port. If no port is specified, 514 is used by default (the
standard syslog port).
- An IPv6 address followed by a colon (':') and optionally a UDP
port. If no port is specified, 514 is used by default (the
standard syslog port).
- A filesystem path to a UNIX domain socket, keeping in mind
considerations for chroot (be sure the path is accessible
inside the chroot) and uid/gid (be sure the path is
appropriately writable).
- A file descriptor number in the form "fd@<number>", which may
point to a pipe, terminal, or socket. In this case unbuffered
logs are used and one writev() call per log is performed. This
is a bit expensive but acceptable for most workloads. Messages
sent this way will not be truncated but may be dropped, in
which case the DroppedLogs counter will be incremented. The
writev() call is atomic even on pipes for messages up to
PIPE_BUF size, which POSIX recommends to be at least 512 and
which is 4096 bytes on most modern operating systems. Any
larger message may be interleaved with messages from other
processes. Exceptionally for debugging purposes the file
descriptor may also be directed to a file, but doing so will
significantly slow HAProxy down as non-blocking calls will be
ignored. Also there will be no way to purge nor rotate this
file without restarting the process. Note that the configured
syslog format is preserved, so the output is suitable for use
with a TCP syslog server. See also the "short" and "raw"
formats below.
- "stdout" / "stderr", which are respectively aliases for "fd@1"
and "fd@2", see above.
- A ring buffer in the form "ring@<name>", which will correspond
to an in-memory ring buffer accessible over the CLI using the
"show events" command, which will also list existing rings and
their sizes. Such buffers are lost on reload or restart but
when used as a complement this can help troubleshooting by
having the logs instantly available.
- A log backend in the form "backend@<name>", which will send
log messages to the corresponding log backend responsible for
sending the message to the proper server according to the
backend's lb settings. A log backend is a backend section with
"mode log" set (see "mode" for more information).
- An explicit stream address prefix such as "tcp@","tcp6@",
"tcp4@" or "uxst@" will allocate an implicit ring buffer with
a stream forward server targeting the given address.
You may want to reference some environment variables in the
address parameter, see section 2.3 about environment variables.
<length> is an optional maximum line length. Log lines larger than this
value will be truncated before being sent. The reason is that
syslog servers act differently on log line length. All servers
support the default value of 1024, but some servers simply drop
larger lines while others do log them. If a server supports long
lines, it may make sense to set this value here in order to avoid
truncating long lines. Similarly, if a server drops long lines,
it is preferable to truncate them before sending them. Accepted
values are 80 to 65535 inclusive. The default value of 1024 is
generally fine for all standard usages. Some specific cases of
long captures or JSON-formatted logs may require larger values.
You may also need to increase "tune.http.logurilen" if your
request URIs are truncated.
<ranges> A list of comma-separated ranges to identify the logs to sample.
This is used to balance the load of the logs to send to the log
server. The limits of the ranges cannot be null. They are numbered
from 1. The size or period (in number of logs) of the sample must
be set with <sample_size> parameter.
<sample_size>
The size of the sample in number of logs to consider when balancing
their logging loads. It is used to balance the load of the logs to
send to the syslog server. This size must be greater or equal to the
maximum of the high limits of the ranges.
(see also <ranges> parameter).
<format> is the log format used when generating syslog messages. It may be
one of the following :
local Analog to rfc3164 syslog message format except that hostname
field is stripped. This is the default.
Note: option "log-send-hostname" switches the default to
rfc3164.
rfc3164 The RFC3164 syslog message format.
(https://tools.ietf.org/html/rfc3164)
rfc5424 The RFC5424 syslog message format.
(https://tools.ietf.org/html/rfc5424)
priority A message containing only a level plus syslog facility between
angle brackets such as '<63>', followed by the text. The PID,
date, time, process name and system name are omitted. This is
designed to be used with a local log server.
short A message containing only a level between angle brackets such as
'<3>', followed by the text. The PID, date, time, process name
and system name are omitted. This is designed to be used with a
local log server. This format is compatible with what the
systemd logger consumes.
timed A message containing only a level between angle brackets such as
'<3>', followed by ISO date and by the text. The PID, process
name and system name are omitted. This is designed to be
used with a local log server.
iso A message containing only the ISO date, followed by the text.
The PID, process name and system name are omitted. This is
designed to be used with a local log server.
raw A message containing only the text. The level, PID, date, time,
process name and system name are omitted. This is designed to
be used in containers or during development, where the severity
only depends on the file descriptor used (stdout/stderr).
<facility> must be one of the 24 standard syslog facilities :
kern user mail daemon auth syslog lpr news
uucp cron auth2 ftp ntp audit alert cron2
local0 local1 local2 local3 local4 local5 local6 local7
Note that the facility is ignored for the "short" and "raw"
formats, but still required as a positional field. It is
recommended to use "daemon" in this case to make it clear that
it's only supposed to be used locally.
<level> is optional and can be specified to filter outgoing messages. By
default, all messages are sent. If a level is specified, only
messages with a severity at least as important as this level
will be sent. An optional minimum level can be specified. If it
is set, logs emitted with a more severe level than this one will
be capped to this level. This is used to avoid sending "emerg"
messages on all terminals on some default syslog configurations.
Eight levels are known :
emerg alert crit err warning notice info debug
It is important to keep in mind that it is the frontend which decides what to
log from a connection, and that in case of content switching, the log entries
from the backend will be ignored. Connections are logged at level "info".
However, backend log declaration define how and where servers status changes
will be logged. Level "notice" will be used to indicate a server going up,
"warning" will be used for termination signals and definitive service
termination, and "alert" will be used for when a server goes down.
Note : According to RFC3164, messages are truncated to 1024 bytes before
being emitted.
Example :
log global
log stdout format short daemon
log stdout format raw daemon
log stderr format raw daemon notice
log 127.0.0.1:514 local0 notice
log tcp@127.0.0.1:514 local0 notice notice
log "${LOCAL_SYSLOG}:514" local0 notice
Specifies the log format string to use for traffic logs
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
This directive specifies the log format string that will be used for all logs
resulting from traffic passing through the frontend using this line. If the
directive is used in a defaults section, all subsequent frontends will use
the same log format. Please see
section 8.2.6 which covers the custom log
format string in depth.
A specific log-format used only in case of connection error can also be
defined, see the "
error-log-format" option.
"
log-format" directive overrides previous "
option tcplog", "
log-format",
"
option httplog" and "
option httpslog" directives.
Specifies the RFC5424 structured-data log format string
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
This directive specifies the RFC5424 structured-data log format string that
will be used for all logs resulting from traffic passing through the frontend
using this line. If the directive is used in a defaults section, all
subsequent frontends will use the same log format. Please see
section 8.2.6
which covers the log format string in depth.
See https://tools.ietf.org/html/rfc5424#section-6.3 for more information
about the RFC5424 structured-data part.
Note : This log format string will be used only for loggers that have set
log format to "rfc5424".
Example :
log-format-sd [exampleSDID@1234\ bytes=\"%B\"\ status=\"%ST\"]
Specifies the log tag to use for all outgoing logs
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Sets the tag field in the syslog header to this string. It defaults to the
log-tag set in the global section, otherwise the program name as launched
from the command line, which usually is "HAProxy". Sometimes it can be useful
to differentiate between multiple processes running on the same host, or to
differentiate customer instances running in the same process. In the backend,
logs about servers up/down will use this tag. As a hint, it can be convenient
to set a log-tag related to a hosted customer in a defaults section then put
all the frontends and backends for that customer, then start another customer
in a new defaults section. See also the global "
log-tag" directive.
Set the maximum server queue size for maintaining keep-alive connections
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
HTTP keep-alive tries to reuse the same server connection whenever possible,
but sometimes it can be counter-productive, for example if a server has a lot
of connections while other ones are idle. This is especially true for static
servers.
The purpose of this setting is to set a threshold on the number of queued
connections at which HAProxy stops trying to reuse the same server and prefers
to find another one. The default value, -1, means there is no limit. A value
of zero means that keep-alive requests will never be queued. For very close
servers which can be reached with a low latency and which are not sensible to
breaking keep-alive, a low value is recommended (e.g. local static server can
use a value of 10 or less). For remote servers suffering from a high latency,
higher values might be needed to cover for the latency and/or the cost of
picking a different server.
Note that this has no impact on responses which are maintained to the same
server consecutively to a 401 response. They will still go to the same server
even if they have to be queued.
Set the maximum number of outgoing connections we can keep idling for a given
client session. The default is 5 (it precisely equals MAX_SRV_LIST which is
defined at build time).
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Fix the maximum number of concurrent connections on a frontend
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<conns> is the maximum number of concurrent connections the frontend will
accept to serve. Excess connections will be queued by the system
in the socket's listen queue and will be served once a connection
closes.
If the system supports it, it can be useful on big sites to raise this limit
very high so that HAProxy manages connection queues, instead of leaving the
clients with unanswered connection attempts. This value should not exceed the
global maxconn. Also, keep in mind that a connection contains two buffers
of tune.bufsize (16kB by default) each, as well as some other data resulting
in about 33 kB of RAM being consumed per established connection. That means
that a medium system equipped with 1GB of RAM can withstand around
20000-25000 concurrent connections if properly tuned.
Also, when <conns> is set to large values, it is possible that the servers
are not sized to accept such loads, and for this reason it is generally wise
to assign them some reasonable connection limits.
When this value is set to zero, which is the default, the global "
maxconn"
value is used.
Set the running mode or protocol of the instance
May be used in sections :
defaults | frontend | listen | backend |
Arguments :tcp The instance will work in pure TCP mode. A full-duplex connection
will be established between clients and servers, and no layer 7
examination will be performed. This is the default mode. It
should be used for SSL, SSH, SMTP, ...
http The instance will work in HTTP mode. The client request will be
analyzed in depth before connecting to any server. Any request
which is not RFC-compliant will be rejected. Layer 7 filtering,
processing and switching will be possible. This is the mode which
brings HAProxy most of its value.
log When used in a backend section, it will turn the backend into a
log backend. Such backend can be used as a log destination for
any "log" directive by using the "backend@<name>" syntax. Log
messages will be distributed to the servers from the backend
according to the lb settings which can be configured using the
"balance" keyword. Log backends support UDP servers by prefixing
the server's address with the "udp@" prefix. Common backend and
server features are supported, but not TCP or HTTP specific ones.
When doing content switching, it is mandatory that the frontend and the
backend are in the same mode (generally HTTP), otherwise the configuration
will be refused.
Example :
defaults http_instances
mode http
Add a condition to report a failure to a monitor HTTP request.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :if <cond> the monitor request will fail if the condition is satisfied,
and will succeed otherwise. The condition should describe a
combined test which must induce a failure if all conditions
are met, for instance a low number of servers both in a
backend and its backup.
unless <cond> the monitor request will succeed only if the condition is
satisfied, and will fail otherwise. Such a condition may be
based on a test on the presence of a minimum number of active
servers in a list of backends.
This statement adds a condition which can force the response to a monitor
request to report a failure. By default, when an external component queries
the URI dedicated to monitoring, a 200 response is returned. When one of the
conditions above is met, HAProxy will return 503 instead of 200. This is
very useful to report a site failure to an external component which may base
routing advertisements between multiple sites on the availability reported by
HAProxy. In this case, one would rely on an ACL involving the "
nbsrv"
criterion. Note that "
monitor fail" only works in HTTP mode. Both status
messages may be tweaked using "
errorfile" or "
errorloc" if needed.
Example:
frontend www
mode http
acl site_dead nbsrv(dynamic) lt 2
acl site_dead nbsrv(static) lt 2
monitor-uri /site_alive
monitor fail if site_dead
Intercept a URI used by external components' monitor requests
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<uri> is the exact URI which we want to intercept to return HAProxy's
health status instead of forwarding the request.
When an HTTP request referencing <uri> will be received on a frontend,
HAProxy will not forward it nor log it, but instead will return either
"HTTP/1.0 200 OK" or "HTTP/1.0 503 Service unavailable", depending on failure
conditions defined with "
monitor fail". This is normally enough for any
front-end HTTP probe to detect that the service is UP and running without
forwarding the request to a backend server. Note that the HTTP method, the
version and all headers are ignored, but the request must at least be valid
at the HTTP level. This keyword may only be used with an HTTP-mode frontend.
Monitor requests are processed very early, just after the request is parsed
and even before any "
http-request". The only rulesets applied before are the
tcp-request ones. They cannot be logged either, and it is the intended
purpose. Only one URI may be configured for monitoring; when multiple
"
monitor-uri" statements are present, the last one will define the URI to
be used. They are only used to report HAProxy's health to an upper component,
nothing more. However, it is possible to add any number of conditions using
"
monitor fail" and ACLs so that the result can be adjusted to whatever check
can be imagined (most often the number of available servers in a backend).
Note: if <uri> starts by a slash ('/'), the matching is performed against the
request's path instead of the request's uri. It is a workaround to let
the HTTP/2 requests match the monitor-uri. Indeed, in HTTP/2, clients
are encouraged to send absolute URIs only.
Example :
frontend www
mode http
monitor-uri /haproxy_test
Enable or disable early dropping of aborted requests pending in queues.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
In presence of very high loads, the servers will take some time to respond.
The per-instance connection queue will inflate, and the response time will
increase respective to the size of the queue times the average per-stream
response time. When clients will wait for more than a few seconds, they will
often hit the "STOP" button on their browser, leaving a useless request in
the queue, and slowing down other users, and the servers as well, because the
request will eventually be served, then aborted at the first error
encountered while delivering the response.
As there is no way to distinguish between a full STOP and a simple output
close on the client side, HTTP agents should be conservative and consider
that the client might only have closed its output channel while waiting for
the response. However, this introduces risks of congestion when lots of users
do the same, and is completely useless nowadays because probably no client at
all will close the stream while waiting for the response. Some HTTP agents
support this behavior (Squid, Apache, HAProxy), and others do not (TUX, most
hardware-based load balancers). So the probability for a closed input channel
to represent a user hitting the "STOP" button is close to 100%, and the risk
of being the single component to break rare but valid traffic is extremely
low, which adds to the temptation to be able to abort a stream early while
still not served and not pollute the servers.
In HAProxy, the user can choose the desired behavior using the option
"
abortonclose". By default (without the option) the behavior is HTTP
compliant and aborted requests will be served. But when the option is
specified, a stream with an incoming channel closed will be aborted while
it is still possible, either pending in the queue for a connection slot, or
during the connection establishment if the server has not yet acknowledged
the connection request. This considerably reduces the queue size and the load
on saturated servers when users are tempted to click on STOP, which in turn
reduces the response time for other users.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable relaxing of HTTP request parsing
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, HAProxy complies with RFC7230 in terms of message parsing. This
means that invalid characters in header names are not permitted and cause an
error to be returned to the client. This is the desired behavior as such
forbidden characters are essentially used to build attacks exploiting server
weaknesses, and bypass security filtering. Sometimes, a buggy browser or
server will emit invalid header names for whatever reason (configuration,
implementation) and the issue will not be immediately fixed. In such a case,
it is possible to relax HAProxy's header name parser to accept any character
even if that does not make sense, by specifying this option. Similarly, the
list of characters allowed to appear in a URI is well defined by RFC3986, and
chars 0-31, 32 (space), 34 ('"'), 60 ('<'), 62 ('>'), 92 ('\'), 94 ('^'), 96
('`'), 123 ('{'), 124 ('|'), 125 ('}'), 127 (delete) and anything above are
not allowed at all. HAProxy always blocks a number of them (0..32, 127). The
remaining ones are blocked by default unless this option is enabled. This
option also relaxes the test on the HTTP version, it allows HTTP/0.9 requests
to pass through (no version specified), as well as different protocol names
(e.g. RTSP), and multiple digits for both the major and the minor version.
Finally, this option also allows incoming URLs to contain fragment references
('#' after the path).
This option should never be enabled by default as it hides application bugs
and open security breaches. It should only be deployed after a problem has
been confirmed.
When this option is enabled, erroneous header names will still be accepted in
requests, but the complete request will be captured in order to permit later
analysis using the "show errors" request on the UNIX stats socket. Similarly,
requests containing invalid chars in the URI part will be logged. Doing this
also helps confirming that the issue has been solved.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable relaxing of HTTP response parsing
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, HAProxy complies with RFC7230 in terms of message parsing. This
means that invalid characters in header names are not permitted and cause an
error to be returned to the client. This is the desired behavior as such
forbidden characters are essentially used to build attacks exploiting server
weaknesses, and bypass security filtering. Sometimes, a buggy browser or
server will emit invalid header names for whatever reason (configuration,
implementation) and the issue will not be immediately fixed. In such a case,
it is possible to relax HAProxy's header name parser to accept any character
even if that does not make sense, by specifying this option. This option also
relaxes the test on the HTTP version format, it allows multiple digits for
both the major and the minor version.
This option should never be enabled by default as it hides application bugs
and open security breaches. It should only be deployed after a problem has
been confirmed.
When this option is enabled, erroneous header names will still be accepted in
responses, but the complete response will be captured in order to permit
later analysis using the "show errors" request on the UNIX stats socket.
Doing this also helps confirming that the issue has been solved.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Use either all backup servers at a time or only the first one
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, the first operational backup server gets all traffic when normal
servers are all down. Sometimes, it may be preferred to use multiple backups
at once, because one will not be enough. When "
option allbackups" is enabled,
the load balancing will be performed among all backup servers when all normal
ones are unavailable. The same load balancing algorithm will be used and the
servers' weights will be respected. Thus, there will not be any priority
order between the backup servers anymore.
This option is mostly used with static server farms dedicated to return a
"sorry" page when an application is completely offline.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Analyze all server responses and block responses with cacheable cookies
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
Some high-level frameworks set application cookies everywhere and do not
always let enough control to the developer to manage how the responses should
be cached. When a session cookie is returned on a cacheable object, there is a
high risk of session crossing or stealing between users traversing the same
caches. In some situations, it is better to block the response than to let
some sensitive session information go in the wild.
The option "
checkcache" enables deep inspection of all server responses for
strict compliance with HTTP specification in terms of cacheability. It
carefully checks "Cache-control", "Pragma" and "Set-cookie" headers in server
response to check if there's a risk of caching a cookie on a client-side
proxy. When this option is enabled, the only responses which can be delivered
to the client are :
- all those without "Set-Cookie" header;
- all those with a return code other than 200, 203, 204, 206, 300, 301,
404, 405, 410, 414, 501, provided that the server has not set a
"Cache-control: public" header field;
- all those that result from a request using a method other than GET, HEAD,
OPTIONS, TRACE, provided that the server has not set a 'Cache-Control:
public' header field;
- those with a 'Pragma: no-cache' header
- those with a 'Cache-control: private' header
- those with a 'Cache-control: no-store' header
- those with a 'Cache-control: max-age=0' header
- those with a 'Cache-control: s-maxage=0' header
- those with a 'Cache-control: no-cache' header
- those with a 'Cache-control: no-cache="
set-cookie"' header
- those with a 'Cache-control: no-cache="set-cookie,' header
(allowing other fields after set-cookie)
If a response doesn't respect these requirements, then it will be blocked
just as if it was from an "http-response deny" rule, with an "HTTP 502 bad
gateway". The session state shows "PH--" meaning that the proxy blocked the
response during headers processing. Additionally, an alert will be sent in
the logs so that admins are informed that there's something to be fixed.
Due to the high impact on the application, the application should be tested
in depth with the option enabled before going to production. It is also a
good practice to always activate it during tests, even if it is not used in
production, as it will report potentially dangerous application behaviors.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable the sending of TCP keepalive packets on the client side
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When there is a firewall or any session-aware component between a client and
a server, and when the protocol involves very long sessions with long idle
periods (e.g. remote desktops), there is a risk that one of the intermediate
components decides to expire a session which has remained idle for too long.
Enabling socket-level TCP keep-alives makes the system regularly send packets
to the other end of the connection, leaving it active. The delay between
keep-alive probes is controlled by the system only and depends both on the
operating system and its tuning parameters.
It is important to understand that keep-alive packets are neither emitted nor
received at the application level. It is only the network stacks which sees
them. For this reason, even if one side of the proxy already uses keep-alives
to maintain its connection alive, those keep-alive packets will not be
forwarded to the other side of the proxy.
Please note that this has nothing to do with HTTP keep-alive.
Using option "
clitcpka" enables the emission of TCP keep-alive probes on the
client side of a connection, which should help when session expirations are
noticed between HAProxy and a client.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable continuous traffic statistics updates
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, counters used for statistics calculation are incremented
only when a stream finishes. It works quite well when serving small
objects, but with big ones (for example large images or archives) or
with A/V streaming, a graph generated from HAProxy counters looks like
a hedgehog. With this option enabled counters get incremented frequently
along the stream, typically every 5 seconds, which is often enough to
produce clean graphs. Recounting touches a hotpath directly so it is not
not enabled by default, as it can cause a lot of wakeups for very large
session counts and cause a small performance drop.
Enable or disable the implicit HTTP/2 upgrade from an HTTP/1.x client
connection.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, HAProxy is able to implicitly upgrade an HTTP/1.x client
connection to an HTTP/2 connection if the first request it receives from a
given HTTP connection matches the HTTP/2 connection preface (i.e. the string
"PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"). This way, it is possible to support
HTTP/1.x and HTTP/2 clients on a non-SSL connections. This option must be
used to disable the implicit upgrade. Note this implicit upgrade is only
supported for HTTP proxies, thus this option too. Note also it is possible to
force the HTTP/2 on clear connections by specifying "proto h2" on the bind
line. Finally, this option is applied on all bind lines. To disable implicit
HTTP/2 upgrades for a specific bind line, it is possible to use "proto h1".
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable logging of normal, successful connections
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
There are large sites dealing with several thousand connections per second
and for which logging is a major pain. Some of them are even forced to turn
logs off and cannot debug production issues. Setting this option ensures that
normal connections, those which experience no error, no timeout, no retry nor
redispatch, will not be logged. This leaves disk space for anomalies. In HTTP
mode, the response status code is checked and return codes 5xx will still be
logged.
It is strongly discouraged to use this option as most of the time, the key to
complex issues is in the normal logs which will not be logged here. If you
need to separate logs, see the "
log-separate-errors" option instead.
Enable or disable logging of null connections
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
In certain environments, there are components which will regularly connect to
various systems to ensure that they are still alive. It can be the case from
another load balancer as well as from monitoring systems. By default, even a
simple port probe or scan will produce a log. If those connections pollute
the logs too much, it is possible to enable option "
dontlognull" to indicate
that a connection on which no data has been transferred will not be logged,
which typically corresponds to those probes. Note that errors will still be
returned to the client and accounted for in the stats. If this is not what is
desired, option http-ignore-probes can be used instead.
It is generally recommended not to use this option in uncontrolled
environments (e.g. internet), otherwise scans and other malicious activities
would not be logged.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
option forwarded [ proto ]
[ host | host-expr <host_expr> ]
[ by | by-expr <by_expr> ] [ by_port | by_port-expr <by_port_expr>]
[ for | for-expr <for_expr> ] [ for_port | for_port-expr <for_port_expr>] Enable insertion of the rfc 7239 forwarded header in requests sent to servers
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<host_expr> optional argument to specify a custom sample expression
those result will be used as 'host' parameter value
<by_expr> optional argument to specicy a custom sample expression
those result will be used as 'by' parameter nodename value
<for_expr> optional argument to specicy a custom sample expression
those result will be used as 'for' parameter nodename value
<by_port_expr> optional argument to specicy a custom sample expression
those result will be used as 'by' parameter nodeport value
<for_port_expr> optional argument to specicy a custom sample expression
those result will be used as 'for' parameter nodeport value
Since HAProxy works in reverse-proxy mode, servers are losing some request
context (request origin: client ip address, protocol used...)
A common way to address this limitation is to use the well known
x-forward-for and x-forward-* friends to expose some of this context to the
underlying servers/applications.
While this use to work and is widely deployed, it is not officially supported
by the IETF and can be the root of some interoperability as well as security
issues.
To solve this, a new HTTP extension has been described by the IETF:
forwarded header (RFC7239).
More information here: https://www.rfc-editor.org/rfc/rfc7239.html
The use of this single header allow to convey numerous details
within the same header, and most importantly, fixes the proxy chaining
issue. (the rfc allows for multiple chained proxies to append their own
values to an already existing header).
This option may be specified in defaults, listen or backend section, but it
will be ignored for frontend sections.
Setting option forwarded without arguments results in using default implicit
behavior.
Default behavior enables proto parameter and injects original client ip.
The equivalent explicit/manual configuration would be:
option forwarded proto for
The keyword 'by' is used to enable 'by' parameter ("nodename") in
forwarded header. It allows to embed request proxy information.
'by' value will be set to proxy ip (destination address)
If not available (ie: UNIX listener), 'by' will be set to
"unknown".
The keyword 'by-expr' is used to enable 'by' parameter ("nodename") in
forwarded header. It allows to embed request proxy information.
'by' value will be set to the result of the sample expression
<by_expr>, if valid, otherwise it will be set to "unknown".
The keyword 'for' is used to enable 'for' parameter ("nodename") in
forwarded header. It allows to embed request client information.
'for' value will be set to client ip (source address)
If not available (ie: UNIX listener), 'for' will be set to
"unknown".
The keyword 'for-expr' is used to enable 'for' parameter ("nodename") in
forwarded header. It allows to embed request client information.
'for' value will be set to the result of the sample expression
<for_expr>, if valid, otherwise it will be set to "unknown".
The keyword 'by_port' is used to provide "nodeport" info to
'by' parameter. 'by_port' requires 'by' or 'by-expr' to be set or
it will be ignored.
"nodeport" will be set to proxy (destination) port if available,
otherwise it will be ignored.
The keyword 'by_port-expr' is used to provide "nodeport" info to
'by' parameter. 'by_port-expr' requires 'by' or 'by-expr' to be set or
it will be ignored.
"nodeport" will be set to the result of the sample expression
<by_port_expr>, if valid, otherwise it will be ignored.
The keyword 'for_port' is used to provide "nodeport" info to
'for' parameter. 'for_port' requires 'for' or 'for-expr' to be set or
it will be ignored.
"nodeport" will be set to client (source) port if available,
otherwise it will be ignored.
The keyword 'for_port-expr' is used to provide "nodeport" info to
'for' parameter. 'for_port-expr' requires 'for' or 'for-expr' to be set or
it will be ignored.
"nodeport" will be set to the result of the sample expression
<for_port_expr>, if valid, otherwise it will be ignored.
Examples :
backend www_default
mode http
option forwarded
backend www_host
mode http
option forwarded host for-expr src,xxh32,hex for_port
backend www_custom
mode http
option forwarded host-expr str(host.com) by-expr str(_haproxy) for for_port-expr int(10)
backend www_for_hide
mode http
option forwarded for-expr rand,hex
Enable insertion of the X-Forwarded-For header to requests sent to servers
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<network> is an optional argument used to disable this option for sources
matching <network>
<name> an optional argument to specify a different "X-Forwarded-For"
header name.
Since HAProxy works in reverse-proxy mode, the servers see its IP address as
their client address. This is sometimes annoying when the client's IP address
is expected in server logs. To solve this problem, the well-known HTTP header
"X-Forwarded-For" may be added by HAProxy to all requests sent to the server.
This header contains a value representing the client's IP address. Since this
header is always appended at the end of the existing header list, the server
must be configured to always use the last occurrence of this header only. See
the server's manual to find how to enable use of this standard header. Note
that only the last occurrence of the header must be used, since it is really
possible that the client has already brought one.
The keyword "header" may be used to supply a different header name to replace
the default "X-Forwarded-For". This can be useful where you might already
have a "X-Forwarded-For" header from a different application (e.g. stunnel),
and you need preserve it. Also if your backend server doesn't use the
"X-Forwarded-For" header and requires different one (e.g. Zeus Web Servers
require "X-Cluster-Client-IP").
Sometimes, a same HAProxy instance may be shared between a direct client
access and a reverse-proxy access (for instance when an SSL reverse-proxy is
used to decrypt HTTPS traffic). It is possible to disable the addition of the
header for a known source address or network by adding the "except" keyword
followed by the network address. In this case, any source IP matching the
network will not cause an addition of this header. Most common uses are with
private networks or 127.0.0.1. IPv4 and IPv6 are both supported.
Alternatively, the keyword "if-none" states that the header will only be
added if it is not present. This should only be used in perfectly trusted
environment, as this might cause a security issue if headers reaching HAProxy
are under the control of the end-user.
This option may be specified either in the frontend or in the backend. If at
least one of them uses it, the header will be added. Note that the backend's
setting of the header subargument takes precedence over the frontend's if
both are defined. In the case of the "if-none" argument, if at least one of
the frontend or the backend does not specify it, it wants the addition to be
mandatory, so it wins.
Example :
frontend www
mode http
option forwardfor except 127.0.0.1
backend www
mode http
option forwardfor header X-Client
Enable or disable the case adjustment of HTTP/1 headers sent to bogus clients
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
There is no standard case for header names because, as stated in RFC7230,
they are case-insensitive. So applications must handle them in a case-
insensitive manner. But some bogus applications violate the standards and
erroneously rely on the cases most commonly used by browsers. This problem
becomes critical with HTTP/2 because all header names must be exchanged in
lower case, and HAProxy follows the same convention. All header names are
sent in lower case to clients and servers, regardless of the HTTP version.
When HAProxy receives an HTTP/1 response, its header names are converted to
lower case and manipulated and sent this way to the clients. If a client is
known to violate the HTTP standards and to fail to process a response coming
from HAProxy, it is possible to transform the lower case header names to a
different format when the response is formatted and sent to the client, by
enabling this option and specifying the list of headers to be reformatted
using the global directives "
h1-case-adjust" or "
h1-case-adjust-file". This
must only be a temporary workaround for the time it takes the client to be
fixed, because clients which require such workarounds might be vulnerable to
content smuggling attacks and must absolutely be fixed.
Please note that this option will not affect standards-compliant clients.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable the case adjustment of HTTP/1 headers sent to bogus servers
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
There is no standard case for header names because, as stated in RFC7230,
they are case-insensitive. So applications must handle them in a case-
insensitive manner. But some bogus applications violate the standards and
erroneously rely on the cases most commonly used by browsers. This problem
becomes critical with HTTP/2 because all header names must be exchanged in
lower case, and HAProxy follows the same convention. All header names are
sent in lower case to clients and servers, regardless of the HTTP version.
When HAProxy receives an HTTP/1 request, its header names are converted to
lower case and manipulated and sent this way to the servers. If a server is
known to violate the HTTP standards and to fail to process a request coming
from HAProxy, it is possible to transform the lower case header names to a
different format when the request is formatted and sent to the server, by
enabling this option and specifying the list of headers to be reformatted
using the global directives "
h1-case-adjust" or "
h1-case-adjust-file". This
must only be a temporary workaround for the time it takes the server to be
fixed, because servers which require such workarounds might be vulnerable to
content smuggling attacks and must absolutely be fixed.
Please note that this option will not affect standards-compliant servers.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable waiting for whole HTTP request body before proceeding
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
It is sometimes desirable to wait for the body of an HTTP request before
taking a decision. This is what is being done by "
balance url_param" for
example. The first use case is to buffer requests from slow clients before
connecting to the server. Another use case consists in taking the routing
decision based on the request body's contents. This option placed in a
frontend or backend forces the HTTP processing to wait until either the whole
body is received or the request buffer is full. It can have undesired side
effects with some applications abusing HTTP by expecting unbuffered
transmissions between the frontend and the backend, so this should definitely
not be used by default.
Enable or disable logging of null connections and request timeouts
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
Recently some browsers started to implement a "pre-connect" feature
consisting in speculatively connecting to some recently visited web sites
just in case the user would like to visit them. This results in many
connections being established to web sites, which end up in 408 Request
Timeout if the timeout strikes first, or 400 Bad Request when the browser
decides to close them first. These ones pollute the log and feed the error
counters. There was already "
option dontlognull" but it's insufficient in
this case. Instead, this option does the following things :
- prevent any 400/408 message from being sent to the client if nothing
was received over a connection before it was closed;
- prevent any log from being emitted in this situation;
- prevent any error counter from being incremented
That way the empty connection is silently ignored. Note that it is better
not to use this unless it is clear that it is needed, because it will hide
real problems. The most common reason for not receiving a request and seeing
a 408 is due to an MTU inconsistency between the client and an intermediary
element such as a VPN, which blocks too large packets. These issues are
generally seen with POST requests as well as GET with large cookies. The logs
are often the only way to detect them.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable HTTP keep-alive from client to server for HTTP/1.x
connections
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent
HTTP/1.x connections: for each connection it processes each request and
response, and leaves the connection idle on both sides. This mode may be
changed by several options such as "
option http-server-close" or "option
httpclose". This option allows to set back the keep-alive mode, which can be
useful when another mode was used in a defaults section.
Setting "
option http-keep-alive" enables HTTP keep-alive mode on the client-
and server- sides. This provides the lowest latency on the client side (slow
network) and the fastest session reuse on the server side at the expense
of maintaining idle connections to the servers. In general, it is possible
with this option to achieve approximately twice the request rate that the
"
http-server-close" option achieves on small objects. There are mainly two
situations where this option may be useful :
- when the server is non-HTTP compliant and authenticates the connection
instead of requests (e.g. NTLM authentication)
- when the cost of establishing the connection to the server is significant
compared to the cost of retrieving the associated object from the server.
This last case can happen when the server is a fast static server of cache.
At the moment, logs will not indicate whether requests came from the same
session or not. The accept date reported in the logs corresponds to the end
of the previous request, and the request time corresponds to the time spent
waiting for a new request. The keep-alive request time is still bound to the
timeout defined by "
timeout http-keep-alive" or "
timeout http-request" if
not set.
This option disables and replaces any previous "
option httpclose" or "option
http-server-close".
Instruct the system to favor low interactive delays over performance in HTTP
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
In HTTP, each payload is unidirectional and has no notion of interactivity.
Any agent is expected to queue data somewhat for a reasonably low delay.
There are some very rare server-to-server applications that abuse the HTTP
protocol and expect the payload phase to be highly interactive, with many
interleaved data chunks in both directions within a single request. This is
absolutely not supported by the HTTP specification and will not work across
most proxies or servers. When such applications attempt to do this through
HAProxy, it works but they will experience high delays due to the network
optimizations which favor performance by instructing the system to wait for
enough data to be available in order to only send full packets. Typical
delays are around 200 ms per round trip. Note that this only happens with
abnormal uses. Normal uses such as CONNECT requests nor WebSockets are not
affected.
When "
option http-no-delay" is present in either the frontend or the backend
used by a connection, all such optimizations will be disabled in order to
make the exchanges as fast as possible. Of course this offers no guarantee on
the functionality, as it may break at any other place. But if it works via
HAProxy, it will work as fast as possible. This option should never be used
by default, and should never be used at all unless such a buggy application
is discovered. The impact of using this option is an increase of bandwidth
usage and CPU usage, which may significantly lower performance in high
latency environments.
Define whether HAProxy will announce keepalive for HTTP/1.x connection to the
server or not
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When running with "
option http-server-close" or "
option httpclose", HAProxy
adds a "Connection: close" header to the HTTP/1.x request forwarded to the
server. Unfortunately, when some servers see this header, they automatically
refrain from using the chunked encoding for responses of unknown length,
while this is totally unrelated. The effect is that a client or a cache could
receive an incomplete response without being aware of it, and consider the
response complete.
By setting "
option http-pretend-keepalive", HAProxy will make the server
believe it will keep the connection alive. The server will then not fall back
to the abnormal undesired above. When HAProxy gets the whole response, it
will close the connection with the server just as it would do with the
"
option httpclose". That way the client gets a normal response and the
connection is correctly closed on the server side.
It is recommended not to enable this option by default, because most servers
will more efficiently close the connection themselves after the last packet,
and release its buffers slightly earlier. Also, the added packet on the
network could slightly reduce the overall peak performance. However it is
worth noting that when this option is enabled, HAProxy will have slightly
less work to do. So if HAProxy is the bottleneck on the whole architecture,
enabling this option might save a few CPU cycles.
This option may be set in backend and listen sections. Using it in a frontend
section will be ignored and a warning will be reported during startup. It is
a backend related option, so there is no real reason to set it on a
frontend.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Set HAProxy policy about HTTP request header names containing characters
outside the "[a-zA-Z0-9-]" charset
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :preserve disable the filtering. It is the default mode for HTTP proxies
with no FastCGI application configured.
delete remove request headers with a name containing a character
outside the "[a-zA-Z0-9-]" charset. It is the default mode for
HTTP backends with a configured FastCGI application.
reject reject the request with a 403-Forbidden response if it contains a
header name with a character outside the "[a-zA-Z0-9-]" charset.
This option may be used to restrict the request header names to alphanumeric
and hyphen characters ([A-Za-z0-9-]). This may be mandatory to interoperate
with non-HTTP compliant servers that fail to handle some characters in header
names. It may also be mandatory for FastCGI applications because all
non-alphanumeric characters in header names are replaced by an underscore
('_'). Thus, it is easily possible to mix up header names and bypass some
rules. For instance, "X-Forwarded-For" and "X_Forwarded-For" headers are both
converted to "HTTP_X_FORWARDED_FOR" in FastCGI.
Note this option is evaluated per proxy and after the http-request rules
evaluation.
Enable or disable HTTP/1.x connection closing on the server side
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent
HTTP/1.x connections: for each connection it processes each request and
response, and leaves the connection idle on both sides. This mode may be
changed by several options such as "
option http-server-close" or "option
httpclose". Setting "
option http-server-close" enables HTTP connection-close
mode on the server side while keeping the ability to support HTTP keep-alive
and pipelining on the client side. This provides the lowest latency on the
client side (slow network) and the fastest session reuse on the server side
to save server resources, similarly to "
option httpclose". It also permits
non-keepalive capable servers to be served in keep-alive mode to the clients
if they conform to the requirements of RFC7230. Please note that some servers
do not always conform to those requirements when they see "Connection: close"
in the request. The effect will be that keep-alive will never be used. A
workaround consists in enabling "
option http-pretend-keepalive".
At the moment, logs will not indicate whether requests came from the same
session or not. The accept date reported in the logs corresponds to the end
of the previous request, and the request time corresponds to the time spent
waiting for a new request. The keep-alive request time is still bound to the
timeout defined by "
timeout http-keep-alive" or "
timeout http-request" if
not set.
This option may be set both in a frontend and in a backend. It is enabled if
at least one of the frontend or backend holding a connection has it enabled.
It disables and replaces any previous "
option httpclose" or "option
http-keep-alive". Please check
section 4 ("Proxies") to see how this option
combines with others when frontend and backend options differ.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Make use of non-standard Proxy-Connection header instead of Connection
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
While RFC7230 explicitly states that HTTP/1.1 agents must use the
Connection header to indicate their wish of persistent or non-persistent
connections, both browsers and proxies ignore this header for proxied
connections and make use of the undocumented, non-standard Proxy-Connection
header instead. The issue begins when trying to put a load balancer between
browsers and such proxies, because there will be a difference between what
HAProxy understands and what the client and the proxy agree on.
By setting this option in a frontend, HAProxy can automatically switch to use
that non-standard header if it sees proxied requests. A proxied request is
defined here as one where the URI begins with neither a '/' nor a '*'. This
is incompatible with the HTTP tunnel mode. Note that this option can only be
specified in a frontend and will affect the request along its whole life.
Also, when this option is set, a request which requires authentication will
automatically switch to use proxy authentication headers if it is itself a
proxied request. That makes it possible to check or enforce authentication in
front of an existing proxy.
This option should normally never be used, except in front of a proxy.
Enables HTTP protocol to check on the servers health
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<method> is the optional HTTP method used with the requests. When not set,
the "OPTIONS" method is used, as it generally requires low server
processing and is easy to filter out from the logs. Any method
may be used, though it is not recommended to invent non-standard
ones.
<uri> is the URI referenced in the HTTP requests. It defaults to " / "
which is accessible by default on almost any server, but may be
changed to any other URI. Query strings are permitted.
<version> is the optional HTTP version string. It defaults to "HTTP/1.0"
but some servers might behave incorrectly in HTTP 1.0, so turning
it to HTTP/1.1 may sometimes help. Note that the Host field is
mandatory in HTTP/1.1, use "http-check send" directive to add it.
By default, server health checks only consist in trying to establish a TCP
connection. When "
option httpchk" is specified, a complete HTTP request is
sent once the TCP connection is established, and responses 2xx and 3xx are
considered valid, while all other ones indicate a server failure, including
the lack of any response.
Combined with "
http-check" directives, it is possible to customize the
request sent during the HTTP health checks or the matching rules on the
response. It is also possible to configure a send/expect sequence, just like
with the directive "
tcp-check" for TCP health checks.
The server configuration is used by default to open connections to perform
HTTP health checks. By it is also possible to overwrite server parameters
using "
http-check connect" rules.
"
httpchk" option does not necessarily require an HTTP backend, it also works
with plain TCP backends. This is particularly useful to check simple scripts
bound to some dedicated ports using the inetd daemon. However, it will always
internally relies on an HTX multiplexer. Thus, it means the request
formatting and the response parsing will be strict.
Examples :
backend https_relay
mode tcp
option httpchk OPTIONS * HTTP/1.1
http-check send hdr Host www
server apache1 192.168.1.1:443 check port 80
Enable or disable HTTP/1.x connection closing
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent
HTTP/1.x connections: for each connection it processes each request and
response, and leaves the connection idle on both sides. This mode may be
changed by several options such as "
option http-server-close" or "option
httpclose".
If "
option httpclose" is set, HAProxy will close the client or the server
connection, depending where the option is set. The frontend is considered for
client connections while the backend is considered for server ones. If the
option is set on a listener, it is applied both on client and server
connections. It will check if a "Connection: close" header is already set in
each direction, and will add one if missing.
This option may also be combined with "
option http-pretend-keepalive", which
will disable sending of the "Connection: close" request header, but will
still cause the connection to be closed once the whole response is received.
It disables and replaces any previous "
option http-server-close" or "option
http-keep-alive".
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable logging of HTTP request, stream state and timers
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :clf if the "clf" argument is added, then the output format will be
the CLF format instead of HAProxy's default HTTP format. You can
use this when you need to feed HAProxy's logs through a specific
log analyzer which only support the CLF format and which is not
extensible.
By default, the log output format is very poor, as it only contains the
source and destination addresses, and the instance name. By specifying
"
option httplog", each log line turns into a much richer format including,
but not limited to, the HTTP request, the connection timers, the stream
status, the connections numbers, the captured headers and cookies, the
frontend, backend and server name, and of course the source address and
ports.
Specifying only "
option httplog" will automatically clear the 'clf' mode
if it was set by default.
"
option httplog" overrides any previous "
log-format" directive.
Enable logging of HTTPS request, stream state and timers
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
By default, the log output format is very poor, as it only contains the
source and destination addresses, and the instance name. By specifying
"
option httpslog", each log line turns into a much richer format including,
but not limited to, the HTTP request, the connection timers, the stream
status, the connections numbers, the captured headers and cookies, the
frontend, backend and server name, the SSL certificate verification and SSL
handshake statuses, and of course the source address and ports.
"
option httpslog" overrides any previous "
log-format" directive.
Enable or disable independent timeout processing for both directions
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, when data is sent over a socket, both the write timeout and the
read timeout for that socket are refreshed, because we consider that there is
activity on that socket, and we have no other means of guessing if we should
receive data or not.
While this default behavior is desirable for almost all applications, there
exists a situation where it is desirable to disable it, and only refresh the
read timeout if there are incoming data. This happens on streams with large
timeouts and low amounts of exchanged data such as telnet session. If the
server suddenly disappears, the output data accumulates in the system's
socket buffers, both timeouts are correctly refreshed, and there is no way
to know the server does not receive them, so we don't timeout. However, when
the underlying protocol always echoes sent data, it would be enough by itself
to detect the issue using the read timeout. Note that this problem does not
happen with more verbose protocols because data won't accumulate long in the
socket buffers.
When this option is set on the frontend, it will disable read timeout updates
on data sent to the client. There probably is little use of this case. When
the option is set on the backend, it will disable read timeout updates on
data sent to the server. Doing so will typically break large HTTP posts from
slow lines, so use it with caution.
Use LDAPv3 health checks for server testing
May be used in the following contexts: tcp
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
It is possible to test that the server correctly talks LDAPv3 instead of just
testing that it accepts the TCP connection. When this option is set, an
LDAPv3 anonymous simple bind message is sent to the server, and the response
is analyzed to find an LDAPv3 bind response message.
The server is considered valid only when the LDAP response contains success
resultCode (http://tools.ietf.org/html/rfc4511#section-4.1.9).
Logging of bind requests is server dependent see your documentation how to
configure it.
Example :
option ldap-check
Use external processes for server health checks
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
It is possible to test the health of a server using an external command.
This is achieved by running the executable set using "external-check
command".
Requires the "
external-check" global to be set.
Avoid closing idle frontend connections if a soft stop is in progress
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, idle connections will be closed during a soft stop. In some
environments, a client talking to the proxy may have prepared some idle
connections in order to send requests later. If there is no proper retry on
write errors, this can result in errors while haproxy is reloading. Even
though a proper implementation should retry on connection/write errors, this
option was introduced to support backwards compatibility with haproxy prior
to version 2.4. Indeed before v2.4, haproxy used to wait for a last request
and response to add a "connection: close" header before closing, thus
notifying the client that the connection would not be reusable.
In a real life example, this behavior was seen in AWS using the ALB in front
of a haproxy. The end result was ALB sending 502 during haproxy reloads.
Users are warned that using this option may increase the number of old
processes if connections remain idle for too long. Adjusting the client
timeouts and/or the "
hard-stop-after" parameter accordingly might be
needed in case of frequent reloads.
Enable or disable logging of health checks status updates
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, failed health check are logged if server is UP and successful
health checks are logged if server is DOWN, so the amount of additional
information is limited.
When this option is enabled, any change of the health check status or to
the server's health will be logged, so that it becomes possible to know
that a server was failing occasional checks before crashing, or exactly when
it failed to respond a valid HTTP status, then when the port started to
reject connections, then when the server stopped responding at all.
Note that status changes not caused by health checks (e.g. enable/disable on
the CLI) are intentionally not logged by this option.
Change log level for non-completely successful connections
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
Sometimes looking for errors in logs is not easy. This option makes HAProxy
raise the level of logs containing potentially interesting information such
as errors, timeouts, retries, redispatches, or HTTP status codes 5xx. The
level changes from "info" to "err". This makes it possible to log them
separately to a different file with most syslog daemons. Be careful not to
remove them from the original file, otherwise you would lose ordering which
provides very important information.
Using this option, large sites dealing with several thousand connections per
second may log normal traffic to a rotating buffer and only archive smaller
error logs.
Enable or disable early logging.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, logs are emitted when all the log format variables and sample
fetches used in the definition of the log-format string return a value, or
when the stream is terminated. This allows the built in log-format strings
to account for the transfer time, or the number of bytes in log messages.
When handling long lived connections such as large file transfers or RDP,
it may take a while for the request or connection to appear in the logs.
Using "
option logasap", the log message is created as soon as the server
connection is established in mode tcp, or as soon as the server sends the
complete headers in mode http. Missing information in the logs will be the
total number of bytes which will only indicate the amount of data transferred
before the message was created and the total time which will not take the
remainder of the connection life or transfer time into account. For the case
of HTTP, it is good practice to capture the Content-Length response header
so that the logs at least indicate how many bytes are expected to be
transferred.
Examples :
listen http_proxy 0.0.0.0:80
mode http
option httplog
option logasap
log 192.168.2.200 local3
>>> Feb 6 12:14:14 localhost \
haproxy[14389]: 10.0.1.2:33317 [06/Feb/2009:12:14:14.655] http-in \
static/srv1 9/10/7/14/+30 200 +243 - - ---- 3/1/1/1/0 1/0 \
"GET /image.iso HTTP/1.0"
Use MySQL health checks for server testing
May be used in the following contexts: tcp
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<username> This is the username which will be used when connecting to MySQL
server.
post-41 Send post v4.1 client compatible checks (the default)
pre-41 Send pre v4.1 client compatible checks
If you specify a username, the check consists of sending two MySQL packet,
one Client Authentication packet, and one QUIT packet, to correctly close
MySQL session. We then parse the MySQL Handshake Initialization packet and/or
Error packet. It is a basic but useful test which does not produce error nor
aborted connect on the server. However, it requires an unlocked authorised
user without a password. To create a basic limited user in MySQL with
optional resource limits:
CREATE USER '<username>'@'<ip_of_haproxy|network_of_haproxy/netmask>'
/*!50701 WITH MAX_QUERIES_PER_HOUR 1 MAX_UPDATES_PER_HOUR 0 */
/*M!100201 MAX_STATEMENT_TIME 0.0001 */;
If you don't specify a username (it is deprecated and not recommended), the
check only consists in parsing the Mysql Handshake Initialization packet or
Error packet, we don't send anything in this mode. It was reported that it
can generate lockout if check is too frequent and/or if there is not enough
traffic. In fact, you need in this case to check MySQL "max_connect_errors"
value as if a connection is established successfully within fewer than MySQL
"max_connect_errors" attempts after a previous connection was interrupted,
the error count for the host is cleared to zero. If HAProxy's server get
blocked, the "FLUSH HOSTS" statement is the only way to unblock it.
Remember that this does not check database presence nor database consistency.
To do this, you can use an external check with xinetd for example.
The check requires MySQL >=3.22, for older version, please use TCP check.
Most often, an incoming MySQL server needs to see the client's IP address for
various purposes, including IP privilege matching and connection logging.
When possible, it is often wise to masquerade the client's IP address when
connecting to the server using the "usesrc" argument of the "
source" keyword,
which requires the transparent proxy feature to be compiled in, and the MySQL
server to route the client via the machine hosting HAProxy.
Enable or disable immediate session resource cleaning after close
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When clients or servers abort connections in a dirty way (e.g. they are
physically disconnected), the session timeouts triggers and the session is
closed. But it will remain in FIN_WAIT1 state for some time in the system,
using some resources and possibly limiting the ability to establish newer
connections.
When this happens, it is possible to activate "
option nolinger" which forces
the system to immediately remove any socket's pending data on close. Thus,
a TCP RST is emitted, any pending data are truncated, and the session is
instantly purged from the system's tables. The generally visible effect for
a client is that responses are truncated if the close happens with a last
block of data (e.g. on a redirect or error response). On the server side,
it may help release the source ports immediately when forwarding a client
aborts in tunnels. In both cases, TCP resets are emitted and given that
the session is instantly destroyed, there will be no retransmit. On a lossy
network this can increase problems, especially when there is a firewall on
the lossy side, because the firewall might see and process the reset (hence
purge its session) and block any further traffic for this session,, including
retransmits from the other side. So if the other side doesn't receive it,
it will never receive any RST again, and the firewall might log many blocked
packets.
For all these reasons, it is strongly recommended NOT to use this option,
unless absolutely needed as a last resort. In most situations, using the
"client-fin" or "server-fin" timeouts achieves similar results with a more
reliable behavior. On Linux it's also possible to use the "
tcp-ut" bind or
server setting.
This option may be used both on frontends and backends, depending on the side
where it is required. Use it on the frontend for clients, and on the backend
for servers. While this option is technically supported in "defaults"
sections, it must really not be used there as it risks to accidentally
propagate to sections that must no use it and to cause problems there.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable insertion of the X-Original-To header to requests sent to servers
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<network> is an optional argument used to disable this option for sources
matching <network>
<name> an optional argument to specify a different "X-Original-To"
header name.
Since HAProxy can work in transparent mode, every request from a client can
be redirected to the proxy and HAProxy itself can proxy every request to a
complex SQUID environment and the destination host from SO_ORIGINAL_DST will
be lost. This is annoying when you want access rules based on destination ip
addresses. To solve this problem, a new HTTP header "X-Original-To" may be
added by HAProxy to all requests sent to the server. This header contains a
value representing the original destination IP address. Since this must be
configured to always use the last occurrence of this header only. Note that
only the last occurrence of the header must be used, since it is really
possible that the client has already brought one.
The keyword "header" may be used to supply a different header name to replace
the default "X-Original-To". This can be useful where you might already
have a "X-Original-To" header from a different application, and you need
preserve it. Also if your backend server doesn't use the "X-Original-To"
header and requires different one.
Sometimes, a same HAProxy instance may be shared between a direct client
access and a reverse-proxy access (for instance when an SSL reverse-proxy is
used to decrypt HTTPS traffic). It is possible to disable the addition of the
header for a known destination address or network by adding the "except"
keyword followed by the network address. In this case, any destination IP
matching the network will not cause an addition of this header. Most common
uses are with private networks or 127.0.0.1. IPv4 and IPv6 are both
supported.
This option may be specified either in the frontend or in the backend. If at
least one of them uses it, the header will be added. Note that the backend's
setting of the header subargument takes precedence over the frontend's if
both are defined.
Examples :
frontend www
mode http
option originalto except 127.0.0.1
backend www
mode http
option originalto header X-Client-Dst
Enable or disable forced persistence on down servers
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When an HTTP request reaches a backend with a cookie which references a dead
server, by default it is redispatched to another server. It is possible to
force the request to be sent to the dead server first using "
option persist"
if absolutely needed. A common use case is when servers are under extreme
load and spend their time flapping. In this case, the users would still be
directed to the server they opened the session on, in the hope they would be
correctly served. It is recommended to use "
option redispatch" in conjunction
with this option so that in the event it would not be possible to connect to
the server at all (server definitely dead), the client would finally be
redirected to another valid server.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Use PostgreSQL health checks for server testing
May be used in the following contexts: tcp
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<username> This is the username which will be used when connecting to
PostgreSQL server.
The check sends a PostgreSQL StartupMessage and waits for either
Authentication request or ErrorResponse message. It is a basic but useful
test which does not produce error nor aborted connect on the server.
This check is identical with the "
mysql-check".
Allow multiple load balanced requests to remain on the same server
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When the load balancing algorithm in use is not deterministic, and a previous
request was sent to a server to which HAProxy still holds a connection, it is
sometimes desirable that subsequent requests on a same session go to the same
server as much as possible. Note that this is different from persistence, as
we only indicate a preference which HAProxy tries to apply without any form
of warranty. The real use is for keep-alive connections sent to servers. When
this option is used, HAProxy will try to reuse the same connection that is
attached to the server instead of rebalancing to another server, causing a
close of the connection. This can make sense for static file servers. It does
not make much sense to use this in combination with hashing algorithms. Note,
HAProxy already automatically tries to stick to a server which sends a 401 or
to a proxy which sends a 407 (authentication required), when the load
balancing algorithm is not deterministic. This is mandatory for use with the
broken NTLM authentication challenge, and significantly helps in
troubleshooting some faulty applications. Option prefer-last-server might be
desirable in these environments as well, to avoid redistributing the traffic
after every other response.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable session redistribution in case of connection failure
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<interval> The optional integer value that controls how often redispatches
occur when retrying connections. Positive value P indicates a
redispatch is desired on every Pth retry, and negative value
N indicate a redispatch is desired on the Nth retry prior to the
last retry. For example, the default of -1 preserves the
historical behavior of redispatching on the last retry, a
positive value of 1 would indicate a redispatch on every retry,
and a positive value of 3 would indicate a redispatch on every
third retry. You can disable redispatches with a value of 0.
In HTTP mode, if a server designated by a cookie is down, clients may
definitely stick to it because they cannot flush the cookie, so they will not
be able to access the service anymore.
Specifying "
option redispatch" will allow the proxy to break cookie or
consistent hash based persistence and redistribute them to a working server.
Active servers are selected from a subset of the list of available
servers. Active servers that are not down or in maintenance (i.e., whose
health is not checked or that have been checked as "up"), are selected in the
following order:
1. Any active, non-backup server, if any, or,
2. If the "
allbackups" option is not set, the first backup server in the
list, or
3. If the "
allbackups" option is set, any backup server.
When a retry occurs, HAProxy tries to select another server than the last
one. The new server is selected from the current list of servers.
Sometimes, if the list is updated between retries (e.g., if numerous retries
occur and last longer than the time needed to check that a server is down,
remove it from the list and fall back on the list of backup servers),
connections may be redirected to a backup server, though.
It also allows to retry connections to another server in case of multiple
connection failures. Of course, it requires having "
retries" set to a nonzero
value.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Use redis health checks for server testing
May be used in the following contexts: tcp
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
It is possible to test that the server correctly talks REDIS protocol instead
of just testing that it accepts the TCP connection. When this option is set,
a PING redis command is sent to the server, and the response is analyzed to
find the "+PONG" response message.
Example :
option redis-check
Use SMTP health checks for server testing
May be used in the following contexts: tcp
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<hello> is an optional argument. It is the "hello" command to use. It can
be either "HELO" (for SMTP) or "EHLO" (for ESMTP). All other
values will be turned into the default command ("HELO").
<domain> is the domain name to present to the server. It may only be
specified (and is mandatory) if the hello command has been
specified. By default, "localhost" is used.
When "
option smtpchk" is set, the health checks will consist in TCP
connections followed by an SMTP command. By default, this command is
"HELO localhost". The server's return code is analyzed and only return codes
starting with a "2" will be considered as valid. All other responses,
including a lack of response will constitute an error and will indicate a
dead server.
This test is meant to be used with SMTP servers or relays. Depending on the
request, it is possible that some servers do not log each connection attempt,
so you may want to experiment to improve the behavior. Using telnet on port
25 is often easier than adjusting the configuration.
Most often, an incoming SMTP server needs to see the client's IP address for
various purposes, including spam filtering, anti-spoofing and logging. When
possible, it is often wise to masquerade the client's IP address when
connecting to the server using the "usesrc" argument of the "
source" keyword,
which requires the transparent proxy feature to be compiled in.
Example :
option smtpchk HELO mydomain.org
Enable or disable collecting & providing separate statistics for each socket.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
Enable or disable automatic kernel acceleration on sockets in both directions
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When this option is enabled either on a frontend or on a backend, HAProxy
will automatically evaluate the opportunity to use kernel tcp splicing to
forward data between the client and the server, in either direction. HAProxy
uses heuristics to estimate if kernel splicing might improve performance or
not. Both directions are handled independently. Note that the heuristics used
are not much aggressive in order to limit excessive use of splicing. This
option requires splicing to be enabled at compile time, and may be globally
disabled with the global option "
nosplice". Since splice uses pipes, using it
requires that there are enough spare pipes.
Important note: kernel-based TCP splicing is a Linux-specific feature which
first appeared in kernel 2.6.25. It offers kernel-based acceleration to
transfer data between sockets without copying these data to user-space, thus
providing noticeable performance gains and CPU cycles savings. Since many
early implementations are buggy, corrupt data and/or are inefficient, this
feature is not enabled by default, and it should be used with extreme care.
While it is not possible to detect the correctness of an implementation,
2.6.29 is the first version offering a properly working implementation. In
case of doubt, splicing may be globally disabled using the global "
nosplice"
keyword.
Example :
option splice-auto
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable automatic kernel acceleration on sockets for requests
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When this option is enabled either on a frontend or on a backend, HAProxy
will use kernel tcp splicing whenever possible to forward data going from
the client to the server. It might still use the recv/send scheme if there
are no spare pipes left. This option requires splicing to be enabled at
compile time, and may be globally disabled with the global option "
nosplice".
Since splice uses pipes, using it requires that there are enough spare pipes.
Important note: see "
option splice-auto" for usage limitations.
Example :
option splice-request
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable automatic kernel acceleration on sockets for responses
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When this option is enabled either on a frontend or on a backend, HAProxy
will use kernel tcp splicing whenever possible to forward data going from
the server to the client. It might still use the recv/send scheme if there
are no spare pipes left. This option requires splicing to be enabled at
compile time, and may be globally disabled with the global option "
nosplice".
Since splice uses pipes, using it requires that there are enough spare pipes.
Important note: see "
option splice-auto" for usage limitations.
Example :
option splice-response
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Use SPOP health checks for server testing
May be used in the following contexts: tcp
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
It is possible to test that the server correctly talks SPOP protocol instead
of just testing that it accepts the TCP connection. When this option is set,
a HELLO handshake is performed between HAProxy and the server, and the
response is analyzed to check no error is reported.
Example :
option spop-check
Enable or disable the sending of TCP keepalive packets on the server side
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When there is a firewall or any session-aware component between a client and
a server, and when the protocol involves very long sessions with long idle
periods (e.g. remote desktops), there is a risk that one of the intermediate
components decides to expire a session which has remained idle for too long.
Enabling socket-level TCP keep-alives makes the system regularly send packets
to the other end of the connection, leaving it active. The delay between
keep-alive probes is controlled by the system only and depends both on the
operating system and its tuning parameters.
It is important to understand that keep-alive packets are neither emitted nor
received at the application level. It is only the network stacks which sees
them. For this reason, even if one side of the proxy already uses keep-alives
to maintain its connection alive, those keep-alive packets will not be
forwarded to the other side of the proxy.
Please note that this has nothing to do with HTTP keep-alive.
Using option "
srvtcpka" enables the emission of TCP keep-alive probes on the
server side of a connection, which should help when session expirations are
noticed between HAProxy and a server.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Use SSLv3 client hello health checks for server testing
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When some SSL-based protocols are relayed in TCP mode through HAProxy, it is
possible to test that the server correctly talks SSL instead of just testing
that it accepts the TCP connection. When "
option ssl-hello-chk" is set, pure
SSLv3 client hello messages are sent once the connection is established to
the server, and the response is analyzed to find an SSL server hello message.
The server is considered valid only when the response contains this server
hello message.
All servers tested till there correctly reply to SSLv3 client hello messages,
and most servers tested do not even log the requests containing only hello
messages, which is appreciable.
Note that this check works even when SSL support was not built into HAProxy
because it forges the SSL message. When SSL support is available, it is best
to use native SSL health checks instead of this one.
Perform health checks using tcp-check send/expect sequences
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
This health check method is intended to be combined with "
tcp-check" command
lists in order to support send/expect types of health check sequences.
TCP checks currently support 4 modes of operations :
- no "
tcp-check" directive : the health check only consists in a connection
attempt, which remains the default mode.
- "
tcp-check send" or "
tcp-check send-binary" only is mentioned : this is
used to send a string along with a connection opening. With some
protocols, it helps sending a "QUIT" message for example that prevents
the server from logging a connection error for each health check. The
check result will still be based on the ability to open the connection
only.
- "
tcp-check expect" only is mentioned : this is used to test a banner.
The connection is opened and HAProxy waits for the server to present some
contents which must validate some rules. The check result will be based
on the matching between the contents and the rules. This is suited for
POP, IMAP, SMTP, FTP, SSH, TELNET.
- both "
tcp-check send" and "
tcp-check expect" are mentioned : this is
used to test a hello-type protocol. HAProxy sends a message, the server
responds and its response is analyzed. the check result will be based on
the matching between the response contents and the rules. This is often
suited for protocols which require a binding or a request/response model.
LDAP, MySQL, Redis and SSL are example of such protocols, though they
already all have their dedicated checks with a deeper understanding of
the respective protocols.
In this mode, many questions may be sent and many answers may be
analyzed.
A fifth mode can be used to insert comments in different steps of the script.
For each tcp-check rule you create, you can add a "comment" directive,
followed by a string. This string will be reported in the log and stderr in
debug mode. It is useful to make user-friendly error reporting. The
"comment" is of course optional.
During the execution of a health check, a variable scope is made available to
store data samples, using the "
tcp-check set-var" operation. Freeing those
variable is possible using "
tcp-check unset-var".
Examples :
option tcp-check
tcp-check expect string +OK\ POP3\ ready comment POP\ protocol
option tcp-check
tcp-check expect string *\ OK\ IMAP4\ ready comment IMAP\ protocol
option tcp-check
tcp-check comment PING\ phase
tcp-check send PING\r\n
tcp-check expect string +PONG
tcp-check comment role\ check
tcp-check send info\ replication\r\n
tcp-check expect string role:master
tcp-check comment QUIT\ phase
tcp-check send QUIT\r\n
tcp-check expect string +OK
forge a HTTP request, then analyze the response
(send many headers before analyzing)
option tcp-check
tcp-check comment forge\ and\ send\ HTTP\ request
tcp-check send HEAD\ /\ HTTP/1.1\r\n
tcp-check send Host:\ www.mydomain.com\r\n
tcp-check send User-Agent:\ HAProxy\ tcpcheck\r\n
tcp-check send \r\n
tcp-check expect rstring HTTP/1\..\ (2..|3..) comment check\ HTTP\ response
Enable or disable the saving of one ACK packet during the accept sequence
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When an HTTP connection request comes in, the system acknowledges it on
behalf of HAProxy, then the client immediately sends its request, and the
system acknowledges it too while it is notifying HAProxy about the new
connection. HAProxy then reads the request and responds. This means that we
have one TCP ACK sent by the system for nothing, because the request could
very well be acknowledged by HAProxy when it sends its response.
For this reason, in HTTP mode, HAProxy automatically asks the system to avoid
sending this useless ACK on platforms which support it (currently at least
Linux). It must not cause any problem, because the system will send it anyway
after 40 ms if the response takes more time than expected to come.
During complex network debugging sessions, it may be desirable to disable
this optimization because delayed ACKs can make troubleshooting more complex
when trying to identify where packets are delayed. It is then possible to
fall back to normal behavior by specifying "
no option tcp-smart-accept".
It is also possible to force it for non-HTTP proxies by simply specifying
"
option tcp-smart-accept". For instance, it can make sense with some services
such as SMTP where the server speaks first.
It is recommended to avoid forcing this option in a defaults section. In case
of doubt, consider setting it back to automatic values by prepending the
"default" keyword before it, or disabling it using the "no" keyword.
Enable or disable the saving of one ACK packet during the connect sequence
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
On certain systems (at least Linux), HAProxy can ask the kernel not to
immediately send an empty ACK upon a connection request, but to directly
send the buffer request instead. This saves one packet on the network and
thus boosts performance. It can also be useful for some servers, because they
immediately get the request along with the incoming connection.
This feature is enabled when "
option tcp-smart-connect" is set in a backend.
It is not enabled by default because it makes network troubleshooting more
complex.
It only makes sense to enable it with protocols where the client speaks first
such as HTTP. In other situations, if there is no data to send in place of
the ACK, a normal ACK is sent.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
Enable or disable the sending of TCP keepalive packets on both sides
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
When there is a firewall or any session-aware component between a client and
a server, and when the protocol involves very long sessions with long idle
periods (e.g. remote desktops), there is a risk that one of the intermediate
components decides to expire a session which has remained idle for too long.
Enabling socket-level TCP keep-alives makes the system regularly send packets
to the other end of the connection, leaving it active. The delay between
keep-alive probes is controlled by the system only and depends both on the
operating system and its tuning parameters.
It is important to understand that keep-alive packets are neither emitted nor
received at the application level. It is only the network stacks which sees
them. For this reason, even if one side of the proxy already uses keep-alives
to maintain its connection alive, those keep-alive packets will not be
forwarded to the other side of the proxy.
Please note that this has nothing to do with HTTP keep-alive.
Using option "
tcpka" enables the emission of TCP keep-alive probes on both
the client and server sides of a connection. Note that this is meaningful
only in "defaults" or "listen" sections. If this option is used in a
frontend, only the client side will get keep-alives, and if this option is
used in a backend, only the server side will get keep-alives. For this
reason, it is strongly recommended to explicitly use "
option clitcpka" and
"
option srvtcpka" when the configuration is split between frontends and
backends.
Enable advanced logging of TCP connections with stream state and timers
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, the log output format is very poor, as it only contains the
source and destination addresses, and the instance name. By specifying
"
option tcplog", each log line turns into a much richer format including, but
not limited to, the connection timers, the stream status, the connections
numbers, the frontend, backend and server name, and of course the source
address and ports. This option is useful for pure TCP proxies in order to
find which of the client or server disconnects or times out. For normal HTTP
proxies, it's better to use "
option httplog" which is even more complete.
"
option tcplog" overrides any previous "
log-format" directive.
Enable client-side transparent proxying
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
This option was introduced in order to provide layer 7 persistence to layer 3
load balancers. The idea is to use the OS's ability to redirect an incoming
connection for a remote address to a local process (here HAProxy), and let
this process know what address was initially requested. When this option is
used, sessions without cookies will be forwarded to the original destination
IP address of the incoming request (which should match that of another
equipment), while requests with cookies will still be forwarded to the
appropriate server.
Note that contrary to a common belief, this option does NOT make HAProxy
present the client's IP to the server when establishing the connection.
Executable to run when performing an external-check
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<command> is the external command to run
The arguments passed to the to the command are:
<proxy_address> <proxy_port> <server_address> <server_port>
The <proxy_address> and <proxy_port> are derived from the first listener
that is either IPv4, IPv6 or a UNIX socket. In the case of a UNIX socket
listener the proxy_address will be the path of the socket and the
<proxy_port> will be the string "NOT_USED". In a backend section, it's not
possible to determine a listener, and both <proxy_address> and <proxy_port>
will have the string value "NOT_USED".
Some values are also provided through environment variables.
Environment variables :
HAPROXY_PROXY_ADDR The first bind address if available (or empty if not
applicable, for example in a "backend" section).
HAPROXY_PROXY_ID The backend id.
HAPROXY_PROXY_NAME The backend name.
HAPROXY_PROXY_PORT The first bind port if available (or empty if not
applicable, for example in a "backend" section or
for a UNIX socket).
HAPROXY_SERVER_ADDR The server address.
HAPROXY_SERVER_CURCONN The current number of connections on the server.
HAPROXY_SERVER_ID The server id.
HAPROXY_SERVER_MAXCONN The server max connections.
HAPROXY_SERVER_NAME The server name.
HAPROXY_SERVER_PORT The server port if available (or empty for a UNIX
socket).
HAPROXY_SERVER_SSL "0" when SSL is not used, "1" when it is used
HAPROXY_SERVER_PROTO The protocol used by this server, which can be one
of "cli" (the haproxy CLI), "syslog" (syslog TCP
server), "
peers" (peers TCP server), "h1" (HTTP/1.x
server), "h2" (HTTP/2 server), or "tcp" (any other
TCP server).
PATH The PATH environment variable used when executing
the command may be set using "
external-check path".
See also "2.3. Environment variables" for other variables.
If the command executed and exits with a zero status then the check is
considered to have passed, otherwise the check is considered to have
failed.
Example :
external-check command /bin/true
The value of the PATH environment variable used when running an external-check
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<path> is the path used when executing external command to run
The default path is "".
Example :
external-check path "/usr/bin:/bin"
Enable RDP cookie-based persistence
May be used in the following contexts: tcp
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the optional name of the RDP cookie to check. If omitted, the
default cookie name "msts" will be used. There currently is no
valid reason to change this name.
This statement enables persistence based on an RDP cookie. The RDP cookie
contains all information required to find the server in the list of known
servers. So when this option is set in the backend, the request is analyzed
and if an RDP cookie is found, it is decoded. If it matches a known server
which is still UP (or if "
option persist" is set), then the connection is
forwarded to this server.
Note that this only makes sense in a TCP backend, but for this to work, the
frontend must have waited long enough to ensure that an RDP cookie is present
in the request buffer. This is the same requirement as with the "rdp-cookie"
load-balancing method. Thus it is highly recommended to put all statements in
a single "listen" section.
Also, it is important to understand that the terminal server will emit this
RDP cookie only if it is configured for "token redirection mode", which means
that the "IP address redirection" option is disabled.
Example :
listen tse-farm
bind :3389
tcp-request inspect-delay 5s
tcp-request content accept if RDP_COOKIE
persist rdp-cookie
balance rdp-cookie
server srv1 1.1.1.1:3389
server srv2 1.1.1.2:3389
Set a limit on the number of new sessions accepted per second on a frontend
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<rate> The <rate> parameter is an integer designating the maximum number
of new sessions per second to accept on the frontend.
When the frontend reaches the specified number of new sessions per second, it
stops accepting new connections until the rate drops below the limit again.
During this time, the pending sessions will be kept in the socket's backlog
(in system buffers) and HAProxy will not even be aware that sessions are
pending. When applying very low limit on a highly loaded service, it may make
sense to increase the socket's backlog using the "
backlog" keyword.
This feature is particularly efficient at blocking connection-based attacks
or service abuse on fragile servers. Since the session rate is measured every
millisecond, it is extremely accurate. Also, the limit applies immediately,
no delay is needed at all to detect the threshold.
Example :
Limit the connection rate on SMTP to 10 per second max
listen smtp
mode tcp
bind :25
rate-limit sessions 10
server smtp1 127.0.0.1:1025
Note : when the maximum rate is reached, the frontend's status is not changed
but its sockets appear as "WAITING" in the statistics if the
"
socket-stats" option is enabled.
Return an HTTP redirection if/unless a condition is matched
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
If/unless the condition is matched, the HTTP request will lead to a redirect
response. If no condition is specified, the redirect applies unconditionally.
Arguments :<loc> With "redirect location", the exact value in <loc> is placed into
the HTTP "Location" header. When used in an "http-request" rule,
<loc> value follows the log-format rules and can include some
dynamic values (see Custom Log Format in section 8.2.6).
<pfx> With "redirect prefix", the "Location" header is built from the
concatenation of <pfx> and the complete URI path, including the
query string, unless the "drop-query" option is specified (see
below). As a special case, if <pfx> equals exactly "/", then
nothing is inserted before the original URI. It allows one to
redirect to the same URL (for instance, to insert a cookie). When
used in an "http-request" rule, <pfx> value follows the log-format
rules and can include some dynamic values (see Custom Log Format
in section 8.2.6).
<sch> With "redirect scheme", then the "Location" header is built by
concatenating <sch> with "://" then the first occurrence of the
"Host" header, and then the URI path, including the query string
unless the "drop-query" option is specified (see below). If no
path is found or if the path is "*", then "/" is used instead. If
no "Host" header is found, then an empty host component will be
returned, which most recent browsers interpret as redirecting to
the same host. This directive is mostly used to redirect HTTP to
HTTPS. When used in an "http-request" rule, <sch> value follows
the log-format rules and can include some dynamic values (see
Custom Log Format in section 8.2.6).
<code> The code is optional. It indicates which type of HTTP redirection
is desired. Only codes 301, 302, 303, 307 and 308 are supported,
with 302 used by default if no code is specified. 301 means
"Moved permanently", and a browser may cache the Location. 302
means "Moved temporarily" and means that the browser should not
cache the redirection. 303 is equivalent to 302 except that the
browser will fetch the location with a GET method. 307 is just
like 302 but makes it clear that the same method must be reused.
Likewise, 308 replaces 301 if the same method must be used.
<option> There are several options which can be specified to adjust the
expected behavior of a redirection :
- "drop-query"
When this keyword is used in a prefix-based redirection, then the
location will be set without any possible query-string, which is useful
for directing users to a non-secure page for instance. It has no effect
with a location-type redirect.
- "append-slash"
This keyword may be used in conjunction with "drop-query" to redirect
users who use a URL not ending with a '/' to the same one with the '/'.
It can be useful to ensure that search engines will only see one URL.
For this, a return code 301 is preferred.
- "ignore-empty"
This keyword only has effect when a location is produced using a log
format expression (i.e. when used in http-request or http-response).
It indicates that if the result of the expression is empty, the rule
should silently be skipped. The main use is to allow mass-redirects
of known paths using a simple map.
- "set-cookie NAME[=value]"
A "Set-Cookie" header will be added with NAME (and optionally "=value")
to the response. This is sometimes used to indicate that a user has
been seen, for instance to protect against some types of DoS. No other
cookie option is added, so the cookie will be a session cookie. Note
that for a browser, a sole cookie name without an equal sign is
different from a cookie with an equal sign.
- "clear-cookie NAME[=]"
A "Set-Cookie" header will be added with NAME (and optionally "="), but
with the "Max-Age" attribute set to zero. This will tell the browser to
delete this cookie. It is useful for instance on logout pages. It is
important to note that clearing the cookie "NAME" will not remove a
cookie set with "NAME=value". You have to clear the cookie "NAME=" for
that, because the browser makes the difference.
Example:
Move the login URL only to HTTPS.
acl clear dst_port 80
acl secure dst_port 8080
acl login_page url_beg /login
acl logout url_beg /logout
acl uid_given url_reg /login?userid=[^&]+
acl cookie_set hdr_sub(cookie) SEEN=1
redirect prefix https://mysite.com set-cookie SEEN=1 if !cookie_set
redirect prefix https://mysite.com if login_page !secure
redirect prefix http://mysite.com drop-query if login_page !uid_given
redirect location http://mysite.com/ if !login_page secure
redirect location / clear-cookie USERID= if logout
Example:
Send redirects for request for articles without a '/'.
acl missing_slash path_reg ^/article/[^/]*$
redirect code 301 prefix / drop-query append-slash if missing_slash
Example:
Redirect all HTTP traffic to HTTPS when SSL is handled by HAProxy.
redirect scheme https if !{ ssl_fc }
Example:
Append 'www.' prefix in front of all hosts not having it
http-request redirect code 301 location \
http://www.%[hdr(host)]%[capture.req.uri] \
unless { hdr_beg(host) -i www }
Example:
Permanently redirect only old URLs to new ones
http-request redirect code 301 location \
%[path,map_str(old-blog-articles.map)] ignore-empty
See
section 7 about ACL usage.
Set the number of retries to perform on a server after a failure
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<value> is the number of times a request or connection attempt should be
retried on a server after a failure.
By default, retries apply only to new connection attempts. However, when
the "
retry-on" directive is used, other conditions might trigger a retry
(e.g. empty response, undesired status code), and each of them will count
one attempt, and when the total number attempts reaches the value here, an
error will be returned.
In order to avoid immediate reconnections to a server which is restarting,
a turn-around timer of min("
timeout connect", one second) is applied before
a retry occurs on the same server.
When "
option redispatch" is set, some retries may be performed on another
server even if a cookie references a different server. By default this will
only be the last retry unless an argument is passed to "
option redispatch".
retry-on [space-delimited list of keywords] Specify when to attempt to automatically retry a failed request.
This setting is only valid when "
mode" is set to http and is silently ignored
otherwise.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<keywords> is a space-delimited list of keywords or HTTP status codes, each
representing a type of failure event on which an attempt to
retry the request is desired. Please read the notes at the
bottom before changing this setting. The following keywords are
supported :
none never retry
conn-failure retry when the connection or the SSL handshake failed
and the request could not be sent. This is the default.
empty-response retry when the server connection was closed after part
of the request was sent, and nothing was received from
the server. This type of failure may be caused by the
request timeout on the server side, poor network
condition, or a server crash or restart while
processing the request.
junk-response retry when the server returned something not looking
like a complete HTTP response. This includes partial
responses headers as well as non-HTTP contents. It
usually is a bad idea to retry on such events, which
may be caused a configuration issue (wrong server port)
or by the request being harmful to the server (buffer
overflow attack for example).
response-timeout the server timeout stroke while waiting for the server
to respond to the request. This may be caused by poor
network condition, the reuse of an idle connection
which has expired on the path, or by the request being
extremely expensive to process. It generally is a bad
idea to retry on such events on servers dealing with
heavy database processing (full scans, etc) as it may
amplify denial of service attacks.
0rtt-rejected retry requests which were sent over early data and were
rejected by the server. These requests are generally
considered to be safe to retry.
<status> any HTTP status code among "401" (Unauthorized), "403"
(Forbidden), "404" (Not Found), "408" (Request Timeout),
"425" (Too Early), "500" (Server Error), "501" (Not
Implemented), "502" (Bad Gateway), "503" (Service
Unavailable), "504" (Gateway Timeout).
all-retryable-errors
retry request for any error that are considered
retryable. This currently activates "conn-failure",
"empty-response", "junk-response", "response-timeout",
"0rtt-rejected", "500", "502", "503", and "504".
Using this directive replaces any previous settings with the new ones; it is
not cumulative.
Please note that using anything other than "none" and "conn-failure" requires
to allocate a buffer and copy the whole request into it, so it has memory and
performance impacts. Requests not fitting in a single buffer will never be
retried (see the global tune.bufsize setting).
You have to make sure the application has a replay protection mechanism built
in such as a unique transaction IDs passed in requests, or that replaying the
same request has no consequence, or it is very dangerous to use any retry-on
value beside "conn-failure" and "none". Static file servers and caches are
generally considered safe against any type of retry. Using a status code can
be useful to quickly leave a server showing an abnormal behavior (out of
memory, file system issues, etc), but in this case it may be a good idea to
immediately redispatch the connection to another server (please see "option
redispatch" for this). Last, it is important to understand that most causes
of failures are the requests themselves and that retrying a request causing a
server to misbehave will often make the situation even worse for this server,
or for the whole service in case of redispatch.
Unless you know exactly how the application deals with replayed requests, you
should not use this directive.
The default is "conn-failure".
Example:
retry-on 503 504
server <name> <address>[:[port]] [param*] Declare a server in a backend
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the internal name assigned to this server. This name will
appear in logs and alerts. If "http-send-name-header" is
set, it will be added to the request header sent to the server.
<address> is the IPv4 or IPv6 address of the server. Alternatively, a
resolvable hostname is supported, but this name will be resolved
during start-up. Address "0.0.0.0" or "*" has a special meaning.
It indicates that the connection will be forwarded to the same IP
address as the one from the client connection. This is useful in
transparent proxy architectures where the client's connection is
intercepted and HAProxy must forward to the original destination
address. This is more or less what the "transparent" keyword does
except that with a server it's possible to limit concurrency and
to report statistics. Optionally, an address family prefix may be
used before the address to force the family regardless of the
address format, which can be useful to specify a path to a unix
socket with no slash ('/'). Currently supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'unix@' -> address is a path to a local unix socket
- 'abns@' -> address is in abstract namespace (Linux only)
- 'sockpair@' -> address is the FD of a connected unix
socket or of a socketpair. During a connection, the
backend creates a pair of connected sockets, and passes
one of them over the FD. The bind part will use the
received socket as the client FD. Should be used
carefully.
- 'rhttp@' [ EXPERIMENTAL ] -> custom address family for a
passive server in HTTP reverse context. This is an
experimental features which requires
"expose-experimental-directives" on a line before this
server.
You may want to reference some environment variables in the
address parameter, see section 2.3 about environment
variables. The "init-addr" setting can be used to modify the way
IP addresses should be resolved upon startup.
<port> is an optional port specification. If set, all connections will
be sent to this port. If unset, the same port the client
connected to will be used. The port may also be prefixed by a "+"
or a "-". In this case, the server's port will be determined by
adding this value to the client's port.
<param*> is a list of parameters for this server. The "server" keywords
accepts an important number of options and has a complete section
dedicated to it. Please refer to section 5 for more details.
Examples :
server first 10.1.1.1:1080 cookie first check inter 1000
server second 10.1.1.2:1080 cookie second check inter 1000
server transp ipv4@
server backup "${SRV_BACKUP}:1080" backup
server www1_dc1 "${LAN_DC1}.101:80"
server www1_dc2 "${LAN_DC2}.101:80"
Note: regarding Linux's abstract namespace sockets, HAProxy uses the whole
sun_path length is used for the address length. Some other programs
such as socat use the string length only by default. Pass the option
",unix-tightsocklen=0" to any abstract socket definition in socat to
make it compatible with HAProxy's.
Set the server state file to read, load and apply to servers available in
this backend.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
It only applies when the directive "
load-server-state-from-file" is set to
"local". When <file> is not provided, if "use-backend-name" is used or if
this directive is not set, then backend name is used. If <file> starts with a
slash '/', then it is considered as an absolute path. Otherwise, <file> is
concatenated to the global directive "
server-state-base".
Example:
The minimal configuration below would make HAProxy look for the state server file '/etc/haproxy/states/bk':
global
server-state-file-base /etc/haproxy/states
backend bk
load-server-state-from-file
Set a template to initialize servers with shared parameters.
The names of these servers are built from <prefix> and <num | range> parameters.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments:<prefix> A prefix for the server names to be built.
<num | range>
If <num> is provided, this template initializes <num> servers
with 1 up to <num> as server name suffixes. A range of numbers
<num_low>-<num_high> may also be used to use <num_low> up to
<num_high> as server name suffixes.
<fqdn> A FQDN for all the servers this template initializes.
<port> Same meaning as "server" <port> argument (see "server" keyword).
<params*>
Remaining server parameters among all those supported by "server"
keyword.
Examples:
server-template srv 1-3 google.com:80 check
server-template srv 3 google.com:80 check
server srv1 google.com:80 check
server srv2 google.com:80 check
server srv3 google.com:80 check
source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | client | clientip } ] source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | hdr_ip(<hdr>[,<occ>]) } ] source <addr>[:<port>] [interface <name>] Set the source address for outgoing connections
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<addr> is the IPv4 address HAProxy will bind to before connecting to a
server. This address is also used as a source for health checks.
The default value of 0.0.0.0 means that the system will select
the most appropriate address to reach its destination. Optionally
an address family prefix may be used before the address to force
the family regardless of the address format, which can be useful
to specify a path to a unix socket with no slash ('/'). Currently
supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'unix@' -> address is a path to a local unix socket
- 'abns@' -> address is in abstract namespace (Linux only)
You may want to reference some environment variables in the
address parameter, see section 2.3 about environment variables.
<port> is an optional port. It is normally not needed but may be useful
in some very specific contexts. The default value of zero means
the system will select a free port. Note that port ranges are not
supported in the backend. If you want to force port ranges, you
have to specify them on each "server" line.
<addr2> is the IP address to present to the server when connections are
forwarded in full transparent proxy mode. This is currently only
supported on some patched Linux kernels. When this address is
specified, clients connecting to the server will be presented
with this address, while health checks will still use the address
<addr>.
<port2> is the optional port to present to the server when connections
are forwarded in full transparent proxy mode (see <addr2> above).
The default value of zero means the system will select a free
port.
<hdr> is the name of a HTTP header in which to fetch the IP to bind to.
This is the name of a comma-separated header list which can
contain multiple IP addresses. By default, the last occurrence is
used. This is designed to work with the X-Forwarded-For header
and to automatically bind to the client's IP address as seen
by previous proxy, typically Stunnel. In order to use another
occurrence from the last one, please see the <occ> parameter
below. When the header (or occurrence) is not found, no binding
is performed so that the proxy's default IP address is used. Also
keep in mind that the header name is case insensitive, as for any
HTTP header.
<occ> is the occurrence number of a value to be used in a multi-value
header. This is to be used in conjunction with "hdr_ip(<hdr>)",
in order to specify which occurrence to use for the source IP
address. Positive values indicate a position from the first
occurrence, 1 being the first one. Negative values indicate
positions relative to the last one, -1 being the last one. This
is helpful for situations where an X-Forwarded-For header is set
at the entry point of an infrastructure and must be used several
proxy layers away. When this value is not specified, -1 is
assumed. Passing a zero here disables the feature.
<name> is an optional interface name to which to bind to for outgoing
traffic. On systems supporting this features (currently, only
Linux), this allows one to bind all traffic to the server to
this interface even if it is not the one the system would select
based on routing tables. This should be used with extreme care.
Note that using this option requires root privileges.
The "
source" keyword is useful in complex environments where a specific
address only is allowed to connect to the servers. It may be needed when a
private address must be used through a public gateway for instance, and it is
known that the system cannot determine the adequate source address by itself.
An extension which is available on certain patched Linux kernels may be used
through the "usesrc" optional keyword. It makes it possible to connect to the
servers with an IP address which does not belong to the system itself. This
is called "full transparent proxy mode". For this to work, the destination
servers have to route their traffic back to this address through the machine
running HAProxy, and IP forwarding must generally be enabled on this machine.
In this "full transparent proxy" mode, it is possible to force a specific IP
address to be presented to the servers. This is not much used in fact. A more
common use is to tell HAProxy to present the client's IP address. For this,
there are two methods :
- present the client's IP and port addresses. This is the most transparent
mode, but it can cause problems when IP connection tracking is enabled on
the machine, because a same connection may be seen twice with different
states. However, this solution presents the huge advantage of not
limiting the system to the 64k outgoing address+port couples, because all
of the client ranges may be used.
- present only the client's IP address and select a spare port. This
solution is still quite elegant but slightly less transparent (downstream
firewalls logs will not match upstream's). It also presents the downside
of limiting the number of concurrent connections to the usual 64k ports.
However, since the upstream and downstream ports are different, local IP
connection tracking on the machine will not be upset by the reuse of the
same session.
This option sets the default source for all servers in the backend. It may
also be specified in a "defaults" section. Finer source address specification
is possible at the server level using the "
source" server option. Refer to
section 5 for more information.
In order to work, "usesrc" requires root privileges, or on supported systems,
the "cap_net_raw" capability. See also the "
setcap" global directive.
Examples :
backend private
source 192.168.1.200
backend transparent_ssl1
source 192.168.1.200 usesrc clientip
backend transparent_ssl2
source 192.168.1.200 usesrc client
backend transparent_ssl3
source 192.168.1.200 usesrc clientip
backend transparent_smtp
source 0.0.0.0 usesrc clientip
backend transparent_http
source 0.0.0.0 usesrc hdr_ip(x-forwarded-for,-1)
Sets the maximum number of keepalive probes TCP should send before dropping
the connection on the server side.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<count> is the maximum number of keepalive probes.
This keyword corresponds to the socket option TCP_KEEPCNT. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_probes) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
Sets the time the connection needs to remain idle before TCP starts sending
keepalive probes, if enabled the sending of TCP keepalive packets on the
server side.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the time the connection needs to remain idle before TCP starts
sending keepalive probes. It is specified in seconds by default,
but can be in any other unit if the number is suffixed by the
unit, as explained at the top of this document.
This keyword corresponds to the socket option TCP_KEEPIDLE. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_time) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
Sets the time between individual keepalive probes on the server side.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the time between individual keepalive probes. It is specified
in seconds by default, but can be in any other unit if the number
is suffixed by the unit, as explained at the top of this
document.
This keyword corresponds to the socket option TCP_KEEPINTVL. If this keyword
is not specified, system-wide TCP parameter (tcp_keepalive_intvl) is used.
The availability of this setting depends on the operating system. It is
known to work on Linux.
Enable statistics admin level if/unless a condition is matched
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
This statement enables the statistics admin level if/unless a condition is
matched.
The admin level allows to enable/disable servers from the web interface. By
default, statistics page is read-only for security reasons.
Currently, the POST request is limited to the buffer size minus the reserved
buffer space, which means that if the list of servers is too long, the
request won't be processed. It is recommended to alter few servers at a
time.
Example :
backend stats_localhost
stats enable
stats admin if LOCALHOST
Example :
backend stats_auth
stats enable
stats auth admin:AdMiN123
stats admin if TRUE
Example :
userlist stats-auth
group admin users admin
user admin insecure-password AdMiN123
group readonly users haproxy
user haproxy insecure-password haproxy
backend stats_auth
stats enable
acl AUTH http_auth(stats-auth)
acl AUTH_ADMIN http_auth_group(stats-auth) admin
stats http-request auth unless AUTH
stats admin if AUTH_ADMIN
Enable statistics with authentication and grant access to an account
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<user> is a user name to grant access to
<passwd> is the cleartext password associated to this user
This statement enables statistics with default settings, and restricts access
to declared users only. It may be repeated as many times as necessary to
allow as many users as desired. When a user tries to access the statistics
without a valid account, a "401 Forbidden" response will be returned so that
the browser asks the user to provide a valid user and password. The real
which will be returned to the browser is configurable using "
stats realm".
Since the authentication method is HTTP Basic Authentication, the passwords
circulate in cleartext on the network. Thus, it was decided that the
configuration file would also use cleartext passwords to remind the users
that those ones should not be sensitive and not shared with any other account.
It is also possible to reduce the scope of the proxies which appear in the
report using "
stats scope".
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable statistics reporting with default settings
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
This statement enables statistics reporting with default settings defined
at build time. Unless stated otherwise, these settings are used :
- stats uri : /haproxy?stats
- stats realm : "HAProxy Statistics"
- stats auth : no authentication
- stats scope : no restriction
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable statistics and hide HAProxy version reporting
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
By default, the stats page reports some useful status information along with
the statistics. Among them is HAProxy's version. However, it is generally
considered dangerous to report precise version to anyone, as it can help them
target known weaknesses with specific attacks. The "
stats hide-version"
statement removes the version from the statistics report. This is recommended
for public sites or any site with a weak login/password.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
stats http-request { allow | deny | auth [realm <realm>] }
[ { if | unless } <condition> ] Access control for statistics
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
As "
http-request", these set of options allow to fine control access to
statistics. Each option may be followed by if/unless and acl.
First option with matched condition (or option without condition) is final.
For "
deny" a 403 error will be returned, for "
allow" normal processing is
performed, for "
auth" a 401/407 error code is returned so the client
should be asked to enter a username and password.
There is no fixed limit to the number of http-request statements per
instance.
Enable statistics and set authentication realm
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<realm> is the name of the HTTP Basic Authentication realm reported to
the browser. The browser uses it to display it in the pop-up
inviting the user to enter a valid username and password.
The realm is read as a single word, so any spaces in it should be escaped
using a backslash ('\').
This statement is useful only in conjunction with "
stats auth" since it is
only related to authentication.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable statistics with automatic refresh
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<delay> is the suggested refresh delay, specified in seconds, which will
be returned to the browser consulting the report page. While the
browser is free to apply any delay, it will generally respect it
and refresh the page this every seconds. The refresh interval may
be specified in any other non-default time unit, by suffixing the
unit after the value, as explained at the top of this document.
This statement is useful on monitoring displays with a permanent page
reporting the load balancer's activity. When set, the HTML report page will
include a link "refresh"/"stop refresh" so that the user can select whether
they want automatic refresh of the page or not.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable statistics and limit access scope
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the name of a listen, frontend or backend section to be
reported. The special name "." (a single dot) designates the
section in which the statement appears.
When this statement is specified, only the sections enumerated with this
statement will appear in the report. All other ones will be hidden. This
statement may appear as many times as needed if multiple sections need to be
reported. Please note that the name checking is performed as simple string
comparisons, and that it is never checked that a give section name really
exists.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
Enable reporting of a description on the statistics page.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
<desc> is an optional description to be reported. If unspecified, the
description from global section is automatically used instead.
This statement is useful for users that offer shared services to their
customers, where node or description should be different for each customer.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters. By default description is not shown.
Example :
backend private_monitoring
stats enable
stats show-desc Master node for Europe, Asia, Africa
stats uri /admin?stats
stats refresh 5s
Enable reporting additional information on the statistics page
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
Enable reporting additional information on the statistics page :
- cap: capabilities (proxy)
- mode: one of tcp, http or health (proxy)
- id: SNMP ID (proxy, socket, server)
- IP (socket, server)
- cookie (backend, server)
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters. Default behavior is not to show this information.
Enable display of extra statistics module on the statistics page
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
New columns are added at the end of the line containing the extra statistics
values as a tooltip.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters. Default behavior is not to show this information.
Enable reporting of a host name on the statistics page.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments:<name> is an optional name to be reported. If unspecified, the
node name from global section is automatically used instead.
This statement is useful for users that offer shared services to their
customers, where node or description might be different on a stats page
provided for each customer. Default behavior is not to show host name.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example:
backend private_monitoring
stats enable
stats show-node Europe-1
stats uri /admin?stats
stats refresh 5s
Enable statistics and define the URI prefix to access them
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<prefix> is the prefix of any URI which will be redirected to stats. This
prefix may contain a question mark ('?') to indicate part of a
query string.
The statistics URI is intercepted on the relayed traffic, so it appears as a
page within the normal application. It is strongly advised to ensure that the
selected URI will never appear in the application, otherwise it will never be
possible to reach it in the application.
The default URI compiled in HAProxy is "/haproxy?stats", but this may be
changed at build time, so it's better to always explicitly specify it here.
It is generally a good idea to include a question mark in the URI so that
intermediate proxies refrain from caching the results. Also, since any string
beginning with the prefix will be accepted as a stats request, the question
mark helps ensuring that no valid URI will begin with the same words.
It is sometimes very convenient to use "/" as the URI prefix, and put that
statement in a "listen" instance of its own. That makes it easy to dedicate
an address or a port to statistics only.
Though this statement alone is enough to enable statistics reporting, it is
recommended to set all other settings in order to avoid relying on default
unobvious parameters.
Example :
backend public_www
server srv1 192.168.0.1:80
stats enable
stats hide-version
stats scope .
stats uri /admin?stats
stats realm HAProxy\ Statistics
stats auth admin1:AdMiN123
stats auth admin2:AdMiN321
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
stick match <pattern> [table <table>] [{if | unless} <cond>] Define a request pattern matching condition to stick a user to a server
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<pattern> is a sample expression rule as described in section 7.3. It
describes what elements of the incoming request or connection
will be analyzed in the hope to find a matching entry in a
stickiness table. This rule is mandatory.
<table> is an optional stickiness table name. If unspecified, the same
backend's table is used. A stickiness table is declared using
the "stick-table" statement.
<cond> is an optional matching condition. It makes it possible to match
on a certain criterion only when other conditions are met (or
not met). For instance, it could be used to match on a source IP
address except when a request passes through a known proxy, in
which case we'd match on a header containing that IP address.
Some protocols or applications require complex stickiness rules and cannot
always simply rely on cookies nor hashing. The "
stick match" statement
describes a rule to extract the stickiness criterion from an incoming request
or connection. See
section 7 for a complete list of possible patterns and
transformation rules.
The table has to be declared using the "
stick-table" statement. It must be of
a type compatible with the pattern. By default it is the one which is present
in the same backend. It is possible to share a table with other backends by
referencing it using the "
table" keyword. If another table is referenced,
the server's ID inside the backends are used. By default, all server IDs
start at 1 in each backend, so the server ordering is enough. But in case of
doubt, it is highly recommended to force server IDs using their "
id" setting.
It is possible to restrict the conditions where a "
stick match" statement
will apply, using "if" or "unless" followed by a condition. See
section 7 for
ACL based conditions.
There is no limit on the number of "
stick match" statements. The first that
applies and matches will cause the request to be directed to the same server
as was used for the request which created the entry. That way, multiple
matches can be used as fallbacks.
The stick rules are checked after the persistence cookies, so they will not
affect stickiness if a cookie has already been used to select a server. That
way, it becomes very easy to insert cookies and match on IP addresses in
order to maintain stickiness between HTTP and HTTPS.
Example :
backend pop
mode tcp
balance roundrobin
stick store-request src
stick-table type ip size 200k expire 30m
server s1 192.168.1.1:110
server s2 192.168.1.1:110
backend smtp
mode tcp
balance roundrobin
stick match src table pop
server s1 192.168.1.1:25
server s2 192.168.1.1:25
stick on <pattern> [table <table>] [{if | unless} <condition>] Define a request pattern to associate a user to a server
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Note : This form is exactly equivalent to "
stick match" followed by
"
stick store-request", all with the same arguments. Please refer
to both keywords for details. It is only provided as a convenience
for writing more maintainable configurations.
Examples :
stick on src table pop if !localhost
stick match src table pop if !localhost
stick store-request src table pop if !localhost
backend http
mode http
balance roundrobin
stick on src table https
cookie SRV insert indirect nocache
server s1 192.168.1.1:80 cookie s1
server s2 192.168.1.1:80 cookie s2
backend https
mode tcp
balance roundrobin
stick-table type ip size 200k expire 30m
stick on src
server s1 192.168.1.1:443
server s2 192.168.1.1:443
Define a request pattern used to create an entry in a stickiness table
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<pattern> is a sample expression rule as described in section 7.3. It
describes what elements of the incoming request or connection
will be analyzed, extracted and stored in the table once a
server is selected.
<table> is an optional stickiness table name. If unspecified, the same
backend's table is used. A stickiness table is declared using
the "stick-table" statement.
<cond> is an optional storage condition. It makes it possible to store
certain criteria only when some conditions are met (or not met).
For instance, it could be used to store the source IP address
except when the request passes through a known proxy, in which
case we'd store a converted form of a header containing that IP
address.
Some protocols or applications require complex stickiness rules and cannot
always simply rely on cookies nor hashing. The "
stick store-request" statement
describes a rule to decide what to extract from the request and when to do
it, in order to store it into a stickiness table for further requests to
match it using the "
stick match" statement. Obviously the extracted part must
make sense and have a chance to be matched in a further request. Storing a
client's IP address for instance often makes sense. Storing an ID found in a
URL parameter also makes sense. Storing a source port will almost never make
any sense because it will be randomly matched. See
section 7 for a complete
list of possible patterns and transformation rules.
The table has to be declared using the "
stick-table" statement. It must be of
a type compatible with the pattern. By default it is the one which is present
in the same backend. It is possible to share a table with other backends by
referencing it using the "
table" keyword. If another table is referenced,
the server's ID inside the backends are used. By default, all server IDs
start at 1 in each backend, so the server ordering is enough. But in case of
doubt, it is highly recommended to force server IDs using their "
id" setting.
It is possible to restrict the conditions where a "
stick store-request"
statement will apply, using "if" or "unless" followed by a condition. This
condition will be evaluated while parsing the request, so any criteria can be
used. See
section 7 for ACL based conditions.
There is no limit on the number of "
stick store-request" statements, but
there is a limit of 8 simultaneous stores per request or response. This
makes it possible to store up to 8 criteria, all extracted from either the
request or the response, regardless of the number of rules. Only the 8 first
ones which match will be kept. Using this, it is possible to feed multiple
tables at once in the hope to increase the chance to recognize a user on
another protocol or access method. Using multiple store-request rules with
the same table is possible and may be used to find the best criterion to rely
on, by arranging the rules by decreasing preference order. Only the first
extracted criterion for a given table will be stored. All subsequent store-
request rules referencing the same table will be skipped and their ACLs will
not be evaluated.
The "store-request" rules are evaluated once the server connection has been
established, so that the table will contain the real server that processed
the request.
Example :
backend pop
mode tcp
balance roundrobin
stick store-request src
stick-table type ip size 200k expire 30m
server s1 192.168.1.1:110
server s2 192.168.1.1:110
backend smtp
mode tcp
balance roundrobin
stick match src table pop
server s1 192.168.1.1:25
server s2 192.168.1.1:25
stick-table type {ip | integer | string [len <length>] | binary [len <length>]}
size
<size> [expire <expire>] [nopurge] [peers <peersect>] [srvkey <srvkey>]
[write-to <wtable>] [store <data_type>]*
Configure the stickiness table for the current section
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : ip a table declared with "type ip" will only store IPv4 addresses.
This form is very compact (about 50 bytes per entry) and allows
very fast entry lookup and stores with almost no overhead. This
is mainly used to store client source IP addresses.
ipv6 a table declared with "type ipv6" will only store IPv6 addresses.
This form is very compact (about 60 bytes per entry) and allows
very fast entry lookup and stores with almost no overhead. This
is mainly used to store client source IP addresses.
integer a table declared with "type integer" will store 32bit integers
which can represent a client identifier found in a request for
instance.
string a table declared with "type string" will store substrings of up
to <len> characters. If the string provided by the pattern
extractor is larger than <len>, it will be truncated before
being stored. During matching, at most <len> characters will be
compared between the string in the table and the extracted
pattern. When not specified, the string is automatically limited
to 32 characters.
binary a table declared with "type binary" will store binary blocks
of <len> bytes. If the block provided by the pattern
extractor is larger than <len>, it will be truncated before
being stored. If the block provided by the sample expression
is shorter than <len>, it will be padded by 0. When not
specified, the block is automatically limited to 32 bytes.
<length> is the maximum number of characters that will be stored in a
"string" type table (See type "string" above). Or the number
of bytes of the block in "binary" type table. Be careful when
changing this parameter as memory usage will proportionally
increase.
<size> is the maximum number of entries that can fit in the table. This
value directly impacts memory usage. Count approximately
50 bytes per entry, plus the size of a string if any. The size
supports suffixes "k", "m", "g" for 2^10, 2^20 and 2^30 factors.
[nopurge] indicates that we refuse to purge older entries when the table
is full. When not specified and the table is full when HAProxy
wants to store an entry in it, it will flush a few of the oldest
entries in order to release some space for the new ones. This is
most often the desired behavior. In some specific cases, it
be desirable to refuse new entries instead of purging the older
ones. That may be the case when the amount of data to store is
far above the hardware limits and we prefer not to offer access
to new clients than to reject the ones already connected. When
using this parameter, be sure to properly set the "expire"
parameter (see below).
<peersect> is the name of the peers section to use for replication. Entries
which associate keys to server IDs are kept synchronized with
the remote peers declared in this section. All entries are also
automatically learned from the local peer (old process) during a
soft restart.
<wtable> is the name of the stick table where peers updates will be
written to in addition to the source table. <wtable> must be of
the same type as the table being defined and must have the same
key length, and source table cannot be used as a target table
itself. Every time an entry update will be received on the source
table through a peer, haproxy will try to refresh related
<wtable> entry. If the entry doesn't exist yet, it will be
created, else its values will be updated as well as its timer.
Note that only types that are not involved in arithmetic ops such
as server_id, server_key and gpt will be written to <wtable> to
prevent processed values from a remote table from interfering with
arithmetic operations performed on the local target table.
(ie: prevent shared cumulative counter from growing indefinitely)
One common use of this option is to be able to use sticking rules
(for server persistence) in a peers cluster setup, because
matching keys will be learned from remote tables.
<expire> defines the maximum duration of an entry in the table since it
was last created, refreshed using 'track-sc' or matched using
'stick match' or 'stick on' rule. The expiration delay is
defined using the standard time format, similarly as the various
timeouts. The maximum duration is slightly above 24 days. See
section 2.5 for more information. If this delay is not specified,
the session won't automatically expire, but older entries will
be removed once full. Be sure not to use the "nopurge" parameter
if not expiration delay is specified.
Note: 'table_*' converters performs lookups but won't update touch
expire since they don't require 'track-sc'.
<srvkey> specifies how each server is identified for the purposes of the
stick table. The valid values are "name" and "addr". If "name" is
given, then <name> argument for the server (may be generated by
a template). If "addr" is given, then the server is identified
by its current network address, including the port. "addr" is
especially useful if you are using service discovery to generate
the addresses for servers with peered stick-tables and want
to consistently use the same host across peers for a stickiness
token.
<data_type> is used to store additional information in the stick-table. This
may be used by ACLs in order to control various criteria related
to the activity of the client matching the stick-table. For each
item specified here, the size of each entry will be inflated so
that the additional data can fit. Several data types may be
stored with an entry. Multiple data types may be specified after
the "store" keyword, as a comma-separated list. Alternatively,
it is possible to repeat the "store" keyword followed by one or
several data types. Except for the "server_id" type which is
automatically detected and enabled, all data types must be
explicitly declared to be stored. If an ACL references a data
type which is not stored, the ACL will simply not match. Some
data types require an argument which must be passed just after
the type between parenthesis. See below for the supported data
types and their arguments.
The data types that can be stored with an entry are the following :
- server_id : this is an integer which holds the numeric ID of the server a
request was assigned to. It is used by the "
stick match", "stick store",
and "
stick on" rules. It is automatically enabled when referenced.
- gpc(<nb>) : General Purpose Counters Array of <nb> elements. This is an
array of positive 32-bit integers which may be used to count anything.
Most of the time they will be used as a incremental counters on some
entries, for instance to note that a limit is reached and trigger some
actions. This array is limited to a maximum of 100 elements:
gpc0 to gpc99, to ensure that the build of a peer update
message can fit into the buffer. Users should take in consideration
that a large amount of counters will increase the data size and the
traffic load using peers protocol since all data/counters are pushed
each time any of them is updated.
This data_type will exclude the usage of the legacy data_types 'gpc0'
and 'gpc1' on the same table. Using the 'gpc' array data_type, all 'gpc0'
and 'gpc1' related fetches and actions will apply to the two first
elements of this array.
- gpc_rate(<nb>,<period>) : Array of increment rates of General Purpose
Counters over a period. Those elements are positive 32-bit integers which
may be used for anything. Just like <gpc>, the count events, but instead
of keeping a cumulative number, they maintain the rate at which the
counter is incremented. Most of the time it will be used to measure the
frequency of occurrence of certain events (e.g. requests to a specific
URL). This array is limited to a maximum of 100 elements: gpt(100)
allowing the storage of gpc0 to gpc99, to ensure that the build of a peer
update message can fit into the buffer.
The array cannot contain less than 1 element: use gpc(1) if you want to
store only the counter gpc0.
Users should take in consideration that a large amount of
counters will increase the data size and the traffic load using peers
protocol since all data/counters are pushed each time any of them is
updated.
This data_type will exclude the usage of the legacy data_types
'gpc0_rate' and 'gpc1_rate' on the same table. Using the 'gpc_rate'
array data_type, all 'gpc0' and 'gpc1' related fetches and actions
will apply to the two first elements of this array.
- gpc0 : first General Purpose Counter. It is a positive 32-bit integer
integer which may be used for anything. Most of the time it will be used
to put a special tag on some entries, for instance to note that a
specific behavior was detected and must be known for future matches.
- gpc0_rate(<period>) : increment rate of the first General Purpose Counter
over a period. It is a positive 32-bit integer integer which may be used
for anything. Just like <gpc0>, it counts events, but instead of keeping
a cumulative number, it maintains the rate at which the counter is
incremented. Most of the time it will be used to measure the frequency of
occurrence of certain events (e.g. requests to a specific URL).
- gpc1 : second General Purpose Counter. It is a positive 32-bit integer
integer which may be used for anything. Most of the time it will be used
to put a special tag on some entries, for instance to note that a
specific behavior was detected and must be known for future matches.
- gpc1_rate(<period>) : increment rate of the second General Purpose Counter
over a period. It is a positive 32-bit integer integer which may be used
for anything. Just like <gpc1>, it counts events, but instead of keeping
a cumulative number, it maintains the rate at which the counter is
incremented. Most of the time it will be used to measure the frequency of
occurrence of certain events (e.g. requests to a specific URL).
- gpt(<nb>) : General Purpose Tags Array of <nb> elements. This is an array
of positive 32-bit integers which may be used for anything.
Most of the time they will be used to put a special tags on some entries,
for instance to note that a specific behavior was detected and must be
known for future matches. This array is limited to a maximum of 100
elements: gpt(100) allowing the storage of gpt0 to gpt99, to ensure that
the build of a peer update message can fit into the buffer.
The array cannot contain less than 1 element: use gpt(1) if you want to
to store only the tag gpt0.
Users should take in consideration that a large amount of counters will
increase the data size and the traffic load using peers protocol since
all data/counters are pushed each time any of them is updated.
This data_type will exclude the usage of the legacy data_type 'gpt0'
on the same table. Using the 'gpt' array data_type, all 'gpt0' related
fetches and actions will apply to the first element of this array.
- gpt0 : first General Purpose Tag. It is a positive 32-bit integer
integer which may be used for anything. Most of the time it will be used
to put a special tag on some entries, for instance to note that a
specific behavior was detected and must be known for future matches
- conn_cnt : Connection Count. It is a positive 32-bit integer which counts
the absolute number of connections received from clients which matched
this entry. It does not mean the connections were accepted, just that
they were received.
- conn_cur : Current Connections. It is a positive 32-bit integer which
stores the concurrent connection counts for the entry. It is incremented
once an incoming connection matches the entry, and decremented once the
connection leaves. That way it is possible to know at any time the exact
number of concurrent connections for an entry.
- conn_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
incoming connection rate over that period, in connections per period. The
result is an integer which can be matched using ACLs.
- sess_cnt : Session Count. It is a positive 32-bit integer which counts
the absolute number of sessions received from clients which matched this
entry. A session is a connection that was accepted by the layer 4 rules.
- sess_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
incoming session rate over that period, in sessions per period. The
result is an integer which can be matched using ACLs.
- http_req_cnt : HTTP request Count. It is a positive 32-bit integer which
counts the absolute number of HTTP requests received from clients which
matched this entry. It does not matter whether they are valid requests or
not. Note that this is different from sessions when keep-alive is used on
the client side.
- http_req_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
HTTP request rate over that period, in requests per period. The result is
an integer which can be matched using ACLs. It does not matter whether
they are valid requests or not. Note that this is different from sessions
when keep-alive is used on the client side.
- http_err_cnt : HTTP Error Count. It is a positive 32-bit integer which
counts the absolute number of HTTP requests errors induced by clients
which matched this entry. Errors are counted on invalid and truncated
requests, as well as on denied or tarpitted requests, and on failed
authentications. If the server responds with 4xx, then the request is
also counted as an error since it's an error triggered by the client
(e.g. vulnerability scan).
- http_err_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
HTTP request error rate over that period, in requests per period (see
http_err_cnt above for what is accounted as an error). The result is an
integer which can be matched using ACLs.
- http_fail_cnt : HTTP Failure Count. It is a positive 32-bit integer which
counts the absolute number of HTTP response failures induced by servers
which matched this entry. Errors are counted on invalid and truncated
responses, as well as any 5xx response other than 501 or 505. It aims at
being used combined with path or URI to detect service failures.
- http_fail_rate(<period>) : frequency counter (takes 12 bytes). It takes
an integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
HTTP response failure rate over that period, in requests per period (see
http_fail_cnt above for what is accounted as a failure). The result is an
integer which can be matched using ACLs.
- bytes_in_cnt : client to server byte count. It is a positive 64-bit
integer which counts the cumulative number of bytes received from clients
which matched this entry. Headers are included in the count. This may be
used to limit abuse of upload features on photo or video servers.
- bytes_in_rate(<period>) : frequency counter (takes 12 bytes). It takes an
integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
incoming bytes rate over that period, in bytes per period. It may be used
to detect users which upload too much and too fast. Warning: with large
uploads, it is possible that the amount of uploaded data will be counted
once upon termination, thus causing spikes in the average transfer speed
instead of having a smooth one. This may partially be smoothed with
"
option contstats" though this is not perfect yet. Use of byte_in_cnt is
recommended for better fairness.
- bytes_out_cnt : server to client byte count. It is a positive 64-bit
integer which counts the cumulative number of bytes sent to clients which
matched this entry. Headers are included in the count. This may be used
to limit abuse of bots sucking the whole site.
- bytes_out_rate(<period>) : frequency counter (takes 12 bytes). It takes
an integer parameter <period> which indicates in milliseconds the length
of the period over which the average is measured. It reports the average
outgoing bytes rate over that period, in bytes per period. It may be used
to detect users which download too much and too fast. Warning: with large
transfers, it is possible that the amount of transferred data will be
counted once upon termination, thus causing spikes in the average
transfer speed instead of having a smooth one. This may partially be
smoothed with "
option contstats" though this is not perfect yet. Use of
byte_out_cnt is recommended for better fairness.
There is only one stick-table per proxy. At the moment of writing this doc,
it does not seem useful to have multiple tables per proxy. If this happens
to be required, simply create a dummy backend with a stick-table in it and
reference it.
It is important to understand that stickiness based on learning information
has some limitations, including the fact that all learned associations are
lost upon restart unless peers are properly configured to transfer such
information upon restart (recommended). In general it can be good as a
complement but not always as an exclusive stickiness.
Last, memory requirements may be important when storing many data types.
Indeed, storing all indicators above at once in each entry requires 116 bytes
per entry, or 116 MB for a 1-million entries table. This is definitely not
something that can be ignored.
Example:
stick-table type ip size 1m expire 5m store gpc0,conn_rate(30s)
Define a response pattern used to create an entry in a stickiness table
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<pattern> is a sample expression rule as described in section 7.3. It
describes what elements of the response or connection will
be analyzed, extracted and stored in the table once a
server is selected.
<table> is an optional stickiness table name. If unspecified, the same
backend's table is used. A stickiness table is declared using
the "stick-table" statement.
<cond> is an optional storage condition. It makes it possible to store
certain criteria only when some conditions are met (or not met).
For instance, it could be used to store the SSL session ID only
when the response is a SSL server hello.
Some protocols or applications require complex stickiness rules and cannot
always simply rely on cookies nor hashing. The "
stick store-response"
statement describes a rule to decide what to extract from the response and
when to do it, in order to store it into a stickiness table for further
requests to match it using the "
stick match" statement. Obviously the
extracted part must make sense and have a chance to be matched in a further
request. Storing an ID found in a header of a response makes sense.
See
section 7 for a complete list of possible patterns and transformation
rules.
The table has to be declared using the "
stick-table" statement. It must be of
a type compatible with the pattern. By default it is the one which is present
in the same backend. It is possible to share a table with other backends by
referencing it using the "
table" keyword. If another table is referenced,
the server's ID inside the backends are used. By default, all server IDs
start at 1 in each backend, so the server ordering is enough. But in case of
doubt, it is highly recommended to force server IDs using their "
id" setting.
It is possible to restrict the conditions where a "
stick store-response"
statement will apply, using "if" or "unless" followed by a condition. This
condition will be evaluated while parsing the response, so any criteria can
be used. See
section 7 for ACL based conditions.
There is no limit on the number of "
stick store-response" statements, but
there is a limit of 8 simultaneous stores per request or response. This
makes it possible to store up to 8 criteria, all extracted from either the
request or the response, regardless of the number of rules. Only the 8 first
ones which match will be kept. Using this, it is possible to feed multiple
tables at once in the hope to increase the chance to recognize a user on
another protocol or access method. Using multiple store-response rules with
the same table is possible and may be used to find the best criterion to rely
on, by arranging the rules by decreasing preference order. Only the first
extracted criterion for a given table will be stored. All subsequent store-
response rules referencing the same table will be skipped and their ACLs will
not be evaluated. However, even if a store-request rule references a table, a
store-response rule may also use the same table. This means that each table
may learn exactly one element from the request and one element from the
response at once.
The table will contain the real server that processed the request.
Example :
backend https
mode tcp
balance roundrobin
stick-table type binary len 32 size 30k expire 30m
acl clienthello req.ssl_hello_type 1
acl serverhello res.ssl_hello_type 2
tcp-request inspect-delay 5s
tcp-request content accept if clienthello
tcp-response content accept if serverhello
stick on req.payload_lv(43,1) if clienthello
stick store-response resp.payload_lv(43,1) if serverhello
server s1 192.168.1.1:443
server s2 192.168.1.1:443
Defines a comment for the following the tcp-check rule, reported in logs if
it fails.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<string> is the comment message to add in logs if the following tcp-check
rule fails.
It only works for connect, send and expect rules. It is useful to make
user-friendly error reporting.
tcp-check connect [default] [port <expr>] [addr <ip>] [send-proxy] [via-socks4]
[ssl] [sni <sni>] [alpn <alpn>] [linger]
[proto <name>] [comment <msg>] Opens a new connection
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
default Use default options of the server line to do the health
checks. The server options are used only if not redefined.
port <expr> if not set, check port or server port is used.
It tells HAProxy where to open the connection to.
<port> must be a valid TCP port source integer, from 1 to
65535 or an sample-fetch expression.
addr <ip> defines the IP address to do the health check.
send-proxy send a PROXY protocol string
via-socks4 enables outgoing health checks using upstream socks4 proxy.
ssl opens a ciphered connection
sni <sni> specifies the SNI to use to do health checks over SSL.
alpn <alpn> defines which protocols to advertise with ALPN. The protocol
list consists in a comma-delimited list of protocol names,
for instance: "http/1.1,http/1.0" (without quotes).
If it is not set, the server ALPN is used.
proto <name> forces the multiplexer's protocol to use for this connection.
It must be a TCP mux protocol and it must be usable on the
backend side. The list of available protocols is reported in
haproxy -vv.
linger cleanly close the connection instead of using a single RST.
When an application lies on more than a single TCP port or when HAProxy
load-balance many services in a single backend, it makes sense to probe all
the services individually before considering a server as operational.
When there are no TCP port configured on the server line neither server port
directive, then the 'tcp-check connect port <port>' must be the first step
of the sequence.
In a tcp-check ruleset a 'connect' is required, it is also mandatory to start
the ruleset with a 'connect' rule. Purpose is to ensure admin know what they
do.
When a connect must start the ruleset, if may still be preceded by set-var,
unset-var or comment rules.
Examples :
option tcp-check
tcp-check connect
tcp-check send GET\ /\ HTTP/1.0\r\n
tcp-check send Host:\ haproxy.1wt.eu\r\n
tcp-check send \r\n
tcp-check expect rstring (2..|3..)
tcp-check connect port 443 ssl
tcp-check send GET\ /\ HTTP/1.0\r\n
tcp-check send Host:\ haproxy.1wt.eu\r\n
tcp-check send \r\n
tcp-check expect rstring (2..|3..)
server www 10.0.0.1 check port 80
option tcp-check
tcp-check connect port 110 linger
tcp-check expect string +OK\ POP3\ ready
tcp-check connect port 143
tcp-check expect string *\ OK\ IMAP4\ ready
server mail 10.0.0.1 check
tcp-check expect [min-recv <int>] [comment <msg>]
[ok-status <st>] [error-status <st>] [tout-status <st>]
[on-success <fmt>] [on-error <fmt>] [status-code <expr>]
[!] <match> <pattern> Specify data to be collected and analyzed during a generic health check
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
min-recv is optional and can define the minimum amount of data required to
evaluate the current expect rule. If the number of received bytes
is under this limit, the check will wait for more data. This
option can be used to resolve some ambiguous matching rules or to
avoid executing costly regex matches on content known to be still
incomplete. If an exact string (string or binary) is used, the
minimum between the string length and this parameter is used.
This parameter is ignored if it is set to -1. If the expect rule
does not match, the check will wait for more data. If set to 0,
the evaluation result is always conclusive.
<match> is a keyword indicating how to look for a specific pattern in the
response. The keyword may be one of "string", "rstring", "binary" or
"rbinary".
The keyword may be preceded by an exclamation mark ("!") to negate
the match. Spaces are allowed between the exclamation mark and the
keyword. See below for more details on the supported keywords.
ok-status <st> is optional and can be used to set the check status if
the expect rule is successfully evaluated and if it is
the last rule in the tcp-check ruleset. "L7OK", "L7OKC",
"L6OK" and "L4OK" are supported :
- L7OK : check passed on layer 7
- L7OKC : check conditionally passed on layer 7, set
server to NOLB state.
- L6OK : check passed on layer 6
- L4OK : check passed on layer 4
By default "L7OK" is used.
error-status <st> is optional and can be used to set the check status if
an error occurred during the expect rule evaluation.
"L7OKC", "L7RSP", "L7STS", "L6RSP" and "L4CON" are
supported :
- L7OKC : check conditionally passed on layer 7, set
server to NOLB state.
- L7RSP : layer 7 invalid response - protocol error
- L7STS : layer 7 response error, for example HTTP 5xx
- L6RSP : layer 6 invalid response - protocol error
- L4CON : layer 1-4 connection problem
By default "L7RSP" is used.
tout-status <st> is optional and can be used to set the check status if
a timeout occurred during the expect rule evaluation.
"L7TOUT", "L6TOUT", and "L4TOUT" are supported :
- L7TOUT : layer 7 (HTTP/SMTP) timeout
- L6TOUT : layer 6 (SSL) timeout
- L4TOUT : layer 1-4 timeout
By default "L7TOUT" is used.
on-success <fmt> is optional and can be used to customize the
informational message reported in logs if the expect
rule is successfully evaluated and if it is the last rule
in the tcp-check ruleset. <fmt> is a log-format string.
on-error <fmt> is optional and can be used to customize the
informational message reported in logs if an error
occurred during the expect rule evaluation. <fmt> is a
log-format string.
status-code <expr> is optional and can be used to set the check status code
reported in logs, on success or on error. <expr> is a
standard HAProxy expression formed by a sample-fetch
followed by some converters.
<pattern> is the pattern to look for. It may be a string or a regular
expression. If the pattern contains spaces, they must be escaped
with the usual backslash ('\').
If the match is set to binary, then the pattern must be passed as
a series of hexadecimal digits in an even number. Each sequence of
two digits will represent a byte. The hexadecimal digits may be
used upper or lower case.
The available matches are intentionally similar to their http-check cousins :
string <string> : test the exact string matches in the response buffer.
A health check response will be considered valid if the
response's buffer contains this exact string. If the
"string" keyword is prefixed with "!", then the response
will be considered invalid if the body contains this
string. This can be used to look for a mandatory pattern
in a protocol response, or to detect a failure when a
specific error appears in a protocol banner.
rstring <regex> : test a regular expression on the response buffer.
A health check response will be considered valid if the
response's buffer matches this expression. If the
"rstring" keyword is prefixed with "!", then the response
will be considered invalid if the body matches the
expression.
string-lf <fmt> : test a log-format string match in the response's buffer.
A health check response will be considered valid if the
response's buffer contains the string resulting of the
evaluation of <fmt>, which follows the log-format rules.
If prefixed with "!", then the response will be
considered invalid if the buffer contains the string.
binary <hexstring> : test the exact string in its hexadecimal form matches
in the response buffer. A health check response will
be considered valid if the response's buffer contains
this exact hexadecimal string.
Purpose is to match data on binary protocols.
rbinary <regex> : test a regular expression on the response buffer, like
"rstring". However, the response buffer is transformed
into its hexadecimal form, including NUL-bytes. This
allows using all regex engines to match any binary
content. The hexadecimal transformation takes twice the
size of the original response. As such, the expected
pattern should work on at-most half the response buffer
size.
binary-lf <hexfmt> : test a log-format string in its hexadecimal form
match in the response's buffer. A health check response
will be considered valid if the response's buffer
contains the hexadecimal string resulting of the
evaluation of <fmt>, which follows the log-format
rules. If prefixed with "!", then the response will be
considered invalid if the buffer contains the
hexadecimal string. The hexadecimal string is converted
in a binary string before matching the response's
buffer.
It is important to note that the responses will be limited to a certain size
defined by the global "
tune.bufsize" option, which defaults to 16384 bytes.
Thus, too large responses may not contain the mandatory pattern when using
"string", "rstring" or binary. If a large response is absolutely required, it
is possible to change the default max size by setting the global variable.
However, it is worth keeping in mind that parsing very large responses can
waste some CPU cycles, especially when regular expressions are used, and that
it is always better to focus the checks on smaller resources. Also, in its
current state, the check will not find any string nor regex past a null
character in the response. Similarly it is not possible to request matching
the null character.
Examples :
option tcp-check
tcp-check expect string +OK\ POP3\ ready
option tcp-check
tcp-check expect string *\ OK\ IMAP4\ ready
option tcp-check
tcp-check send PING\r\n
tcp-check expect string +PONG
tcp-check send info\ replication\r\n
tcp-check expect string role:master
tcp-check send QUIT\r\n
tcp-check expect string +OK
Specify a string or a log-format string to be sent as a question during a
generic health check
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
<data> is the string that will be sent during a generic health
check session.
<fmt> is the log-format string that will be sent, once evaluated,
during a generic health check session.
Examples :
option tcp-check
tcp-check send info\ replication\r\n
tcp-check expect string role:master
Specify an hex digits string or an hex digits log-format string to be sent as
a binary question during a raw tcp health check
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :comment <msg> defines a message to report if the rule evaluation fails.
<hexstring> is the hexadecimal string that will be send, once converted
to binary, during a generic health check session.
<hexfmt> is the hexadecimal log-format string that will be send, once
evaluated and converted to binary, during a generic health
check session.
Examples :
option tcp-check
tcp-check send-binary 50494e470d0a
tcp-check expect binary 2b504F4e47
This operation sets the content of a variable. The variable is declared inline.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<var-name> The name of the variable starts with an indication about its
scope. The scopes allowed for tcp-check are:
"proc" : the variable is shared with the whole process.
"sess" : the variable is shared with the tcp-check session.
"check": the variable is declared for the lifetime of the tcp-check.
This prefix is followed by a name. The separator is a '.'.
The name may only contain characters 'a-z', 'A-Z', '0-9', '.',
and '-'.
<cond> A set of conditions that must all be true for the variable to
actually be set (such as "ifnotempty", "ifgt" ...). See the
set-var converter's description for a full list of possible
conditions.
<expr> Is a sample-fetch expression potentially followed by converters.
<fmt> This is the value expressed using log-format rules (see Custom
Log Format in section 8.2.6).
Examples :
tcp-check set-var(check.port) int(1234)
tcp-check set-var-fmt(check.name) "%H"
Free a reference to a variable within its scope.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<var-name> The name of the variable starts with an indication about its
scope. The scopes allowed for tcp-check are:
"proc" : the variable is shared with the whole process.
"sess" : the variable is shared with the tcp-check session.
"check": the variable is declared for the lifetime of the tcp-check.
This prefix is followed by a name. The separator is a '.'.
The name may only contain characters 'a-z', 'A-Z', '0-9', '.',
and '-'.
Examples :
tcp-check unset-var(check.port)
Perform an action on an incoming connection depending on a layer 4 condition
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<action> defines the action to perform if the condition applies. See
below.
<condition> is a standard layer4-only ACL-based condition (see section 7).
Immediately after acceptance of a new incoming connection, it is possible to
evaluate some conditions to decide whether this connection must be accepted
or dropped or have its counters tracked. Those conditions cannot make use of
any data contents because the connection has not been read from yet, and the
buffers are not yet allocated. This is used to selectively and very quickly
accept or drop connections from various sources with a very low overhead. If
some contents need to be inspected in order to take the decision, the
"
tcp-request content" statements must be used instead.
The "
tcp-request connection" rules are evaluated in their exact declaration
order. If no rule matches or if there is no rule, the default action is to
accept the incoming connection. There is no specific limit to the number of
rules which may be inserted. Any rule may optionally be followed by an
ACL-based condition, in which case it will only be evaluated if the condition
evaluates to true.
The condition is evaluated just before the action is executed, and the action
is performed exactly once. As such, there is no problem if an action changes
an element which is checked as part of the condition. This also means that
multiple actions may rely on the same condition so that the first action that
changes the condition's evaluation is sufficient to implicitly disable the
remaining actions. This is used for example when trying to assign a value to
a variable from various sources when it's empty.
The first keyword after "
tcp-request connection" in the syntax is the rule's
action, optionally followed by a varying number of arguments for the action.
The supported actions and their respective syntaxes are enumerated in
section 4.3 "Actions" (look for actions which tick "TCP RqCon").
This directive is only available from named defaults sections, not anonymous
ones. Rules defined in the defaults section are evaluated before ones in the
associated proxy section. To avoid ambiguities, in this case the same
defaults section cannot be used by proxies with the frontend capability and
by proxies with the backend capability. It means a listen section cannot use
a defaults section defining such rules.
Note that the "if/unless" condition is optional. If no condition is set on
the action, it is simply performed unconditionally. That can be useful for
"track-sc*" actions as well as for changing the default action to a reject.
Example:
Accept all connections from white-listed hosts, reject too fast connection without counting them, and track accepted connections. This results in connection rate being capped from abusive sources.
tcp-request connection accept if { src -f /etc/haproxy/whitelist.lst }
tcp-request connection reject if { src_conn_rate gt 10 }
tcp-request connection track-sc0 src
Example:
Accept all connections from white-listed hosts, count all other connections and reject too fast ones. This results in abusive ones being blocked as long as they don't slow down.
tcp-request connection accept if { src -f /etc/haproxy/whitelist.lst }
tcp-request connection track-sc0 src
tcp-request connection reject if { sc0_conn_rate gt 10 }
Example:
Enable the PROXY protocol for traffic coming from all known proxies.
tcp-request connection expect-proxy layer4 if { src -f proxies.lst }
See
section 7 about ACL usage.
Perform an action on a new session depending on a layer 4-7 condition
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<action> defines the action to perform if the condition applies. See
below.
<condition> is a standard layer 4-7 ACL-based condition (see section 7).
A request's contents can be analyzed at an early stage of request processing
called "TCP content inspection". During this stage, ACL-based rules are
evaluated every time the request contents are updated, until either an
"
accept", a "
reject" or a "
switch-mode" rule matches, or the TCP request
inspection delay expires with no matching rule.
The first difference between these rules and "
tcp-request connection" rules
is that "
tcp-request content" rules can make use of contents to take a
decision. Most often, these decisions will consider a protocol recognition or
validity. The second difference is that content-based rules can be used in
both frontends and backends. In case of HTTP keep-alive with the client, all
tcp-request content rules are evaluated again, so HAProxy keeps a record of
what sticky counters were assigned by a "
tcp-request connection" versus a
"
tcp-request content" rule, and flushes all the content-related ones after
processing an HTTP request, so that they may be evaluated again by the rules
being evaluated again for the next request. This is of particular importance
when the rule tracks some L7 information or when it is conditioned by an
L7-based ACL, since tracking may change between requests.
Content-based rules are evaluated in their exact declaration order. If no
rule matches or if there is no rule, the default action is to accept the
contents. There is no specific limit to the number of rules which may be
inserted.
While there is nothing mandatory about it, it is recommended to use the
track-sc0 in "
tcp-request connection" rules, track-sc1 for "tcp-request
content" rules in the frontend, and track-sc2 for "
tcp-request content"
rules in the backend, because that makes the configuration more readable
and easier to troubleshoot, but this is just a guideline and all counters
may be used everywhere.
The first keyword after "
tcp-request content" in the syntax is the rule's
action, optionally followed by a varying number of arguments for the action.
The supported actions and their respective syntaxes are enumerated in
section 4.3 "Actions" (look for actions which tick "TCP RqCnt").
This directive is only available from named defaults sections, not anonymous
ones. Rules defined in the defaults section are evaluated before ones in the
associated proxy section. To avoid ambiguities, in this case the same
defaults section cannot be used by proxies with the frontend capability and
by proxies with the backend capability. It means a listen section cannot use
a defaults section defining such rules.
Note that the "if/unless" condition is optional. If no condition is set on
the action, it is simply performed unconditionally. That can be useful for
"track-sc*" actions as well as for changing the default action to a reject.
Note also that it is recommended to use a "
tcp-request session" rule to track
information that does *not* depend on Layer 7 contents, especially for HTTP
frontends. Some HTTP processing are performed at the session level and may
lead to an early rejection of the requests. Thus, the tracking at the content
level may be disturbed in such case. A warning is emitted during startup to
prevent, as far as possible, such unreliable usage.
It is perfectly possible to match layer 7 contents with "
tcp-request content"
rules from a TCP proxy, since HTTP-specific ACL matches are able to
preliminarily parse the contents of a buffer before extracting the required
data. If the buffered contents do not parse as a valid HTTP message, then the
ACL does not match. The parser which is involved there is exactly the same
as for all other HTTP processing, so there is no risk of parsing something
differently. In an HTTP frontend or an HTTP backend, it is guaranteed that
HTTP contents will always be immediately present when the rule is evaluated
first because the HTTP parsing is performed in the early stages of the
connection processing, at the session level. But for such proxies, using
"
http-request" rules is much more natural and recommended.
Tracking layer7 information is also possible provided that the information
are present when the rule is processed. The rule processing engine is able to
wait until the inspect delay expires when the data to be tracked is not yet
available.
Example:
tcp-request content use-service lua.deny if { src -f /etc/haproxy/blacklist.lst }
Example:
tcp-request content set-var(sess.my_var) src
tcp-request content set-var-fmt(sess.from) %[src]:%[src_port]
tcp-request content unset-var(sess.my_var2)
Example:
acl is_host_com hdr(Host) -i example.com
tcp-request inspect-delay 30s
tcp-request content accept if is_host_com
tcp-request content reject
acl is_host_com hdr(Host) -i example.com
tcp-request inspect-delay 5s
tcp-request switch-mode http if HTTP
tcp-request reject
...
http-request reject unless is_host_com
Example:
tcp-request inspect-delay 30s
acl content_present req.len gt 0
tcp-request content reject if content_present
tcp-request inspect-delay 30s
acl content_present req.len gt 0
tcp-request content accept if content_present
tcp-request content reject
Example:
tcp-request inspect-delay 10s
tcp-request content track-sc0 hdr(x-forwarded-for,-1)
tcp-request content track-sc0 req.hdr_ip(x-forwarded-for,-1)
Example:
tcp-request inspect-delay 10s
tcp-request content track-sc0 base table req-rate
Example:
Track per-frontend and per-backend counters, block abusers at the frontend when the backend detects abuse(and marks gpc0).
frontend http
stick-table type ip size 1m expire 5m store gpc0
tcp-request connection track-sc0 src
tcp-request connection reject if { sc0_get_gpc0 gt 0 }
...
use_backend http_dynamic if { path_end .php }
backend http_dynamic
stick-table type ip size 1m expire 5m store http_req_rate(10s)
acl click_too_fast sc1_http_req_rate gt 10
acl mark_as_abuser sc0_inc_gpc0(http) gt 0
tcp-request content track-sc1 src
tcp-request content reject if click_too_fast mark_as_abuser
See
section 7 about ACL usage.
Set the maximum allowed time to wait for data during content inspection
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
People using HAProxy primarily as a TCP relay are often worried about the
risk of passing any type of protocol to a server without any analysis. In
order to be able to analyze the request contents, we must first withhold
the data then analyze them. This statement simply enables withholding of
data for at most the specified amount of time.
TCP content inspection applies very early when a connection reaches a
frontend, then very early when the connection is forwarded to a backend. This
means that a connection may experience a first delay in the frontend and a
second delay in the backend if both have tcp-request rules.
Note that when performing content inspection, HAProxy will evaluate the whole
rules for every new chunk which gets in, taking into account the fact that
those data are partial. If no rule matches before the aforementioned delay,
a last check is performed upon expiration, this time considering that the
contents are definitive. If no delay is set, HAProxy will not wait at all
and will immediately apply a verdict based on the available information.
Obviously this is unlikely to be very useful and might even be racy, so such
setups are not recommended.
Note the inspection delay is shortened if an connection error or shutdown is
experienced or if the request buffer appears as full.
As soon as a rule matches, the request is released and continues as usual. If
the timeout is reached and no rule matches, the default policy will be to let
it pass through unaffected.
For most protocols, it is enough to set it to a few seconds, as most clients
send the full request immediately upon connection. Add 3 or more seconds to
cover TCP retransmits but that's all. For some protocols, it may make sense
to use large values, for instance to ensure that the client never talks
before the server (e.g. SMTP), or to wait for a client to talk before passing
data to the server (e.g. SSL). Note that the client timeout must cover at
least the inspection delay, otherwise it will expire first. If the client
closes the connection or if the buffer is full, the delay immediately expires
since the contents will not be able to change anymore.
This directive is only available from named defaults sections, not anonymous
ones. Proxies inherit this value from their defaults section.
Perform an action on a validated session depending on a layer 5 condition
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<action> defines the action to perform if the condition applies. See
below.
<condition> is a standard layer5-only ACL-based condition (see section 7).
Once a session is validated, (i.e. after all handshakes have been completed),
it is possible to evaluate some conditions to decide whether this session
must be accepted or dropped or have its counters tracked. Those conditions
cannot make use of any data contents because no buffers are allocated yet and
the processing cannot wait at this stage. The main use case is to copy some
early information into variables (since variables are accessible in the
session), or to keep track of some information collected after the handshake,
such as SSL-level elements (SNI, ciphers, client cert's CN) or information
from the PROXY protocol header (e.g. track a source forwarded this way). The
extracted information can thus be copied to a variable or tracked using
"track-sc" rules. Of course it is also possible to decide to accept/reject as
with other rulesets. Most operations performed here could also be performed
in "
tcp-request content" rules, except that in HTTP these rules are evaluated
for each new request, and that might not always be acceptable. For example a
rule might increment a counter on each evaluation. It would also be possible
that a country is resolved by geolocation from the source IP address,
assigned to a session-wide variable, then the source address rewritten from
an HTTP header for all requests. If some contents need to be inspected in
order to take the decision, the "
tcp-request content" statements must be used
instead.
The "
tcp-request session" rules are evaluated in their exact declaration
order. If no rule matches or if there is no rule, the default action is to
accept the incoming session. There is no specific limit to the number of
rules which may be inserted.
The first keyword after "
tcp-request session" in the syntax is the rule's
action, optionally followed by a varying number of arguments for the action.
The supported actions and their respective syntaxes are enumerated in
section 4.3 "Actions" (look for actions which tick "TCP RqSes").
This directive is only available from named defaults sections, not anonymous
ones. Rules defined in the defaults section are evaluated before ones in the
associated proxy section. To avoid ambiguities, in this case the same
defaults section cannot be used by proxies with the frontend capability and
by proxies with the backend capability. It means a listen section cannot use
a defaults section defining such rules.
Note that the "if/unless" condition is optional. If no condition is set on
the action, it is simply performed unconditionally. That can be useful for
"track-sc*" actions as well as for changing the default action to a reject.
Example:
Track the original source address by default, or the one advertised in the PROXY protocol header for connection coming from the local proxies. The first connection-level rule enables receipt of the PROXY protocol for these ones, the second rule tracks whatever address we decide to keep after optional decoding.
tcp-request connection expect-proxy layer4 if { src -f proxies.lst }
tcp-request session track-sc0 src
Example:
Accept all sessions from white-listed hosts, reject too fast sessions without counting them, and track accepted sessions. This results in session rate being capped from abusive sources.
tcp-request session accept if { src -f /etc/haproxy/whitelist.lst }
tcp-request session reject if { src_sess_rate gt 10 }
tcp-request session track-sc0 src
Example:
Accept all sessions from white-listed hosts, count all other sessions and reject too fast ones. This results in abusive ones being blocked as long as they don't slow down.
tcp-request session accept if { src -f /etc/haproxy/whitelist.lst }
tcp-request session track-sc0 src
tcp-request session reject if { sc0_sess_rate gt 10 }
See
section 7 about ACL usage.
Perform an action on a session response depending on a layer 4-7 condition
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<action> defines the action to perform if the condition applies. See
below.
<condition> is a standard layer 4-7 ACL-based condition (see section 7).
Response contents can be analyzed at an early stage of response processing
called "TCP content inspection". During this stage, ACL-based rules are
evaluated every time the response contents are updated, until either a final
rule matches, or a TCP response inspection delay is set and expires with no
matching rule.
Most often, these decisions will consider a protocol recognition or validity.
Content-based rules are evaluated in their exact declaration order. If no
rule matches or if there is no rule, the default action is to accept the
contents. There is no specific limit to the number of rules which may be
inserted.
The first keyword after "
tcp-response content" in the syntax is the rule's
action, optionally followed by a varying number of arguments for the action.
The supported actions and their respective syntaxes are enumerated in
section 4.3 "Actions" (look for actions which tick "TCP RsCnt").
This directive is only available from named defaults sections, not anonymous
ones. Rules defined in the defaults section are evaluated before ones in the
associated proxy section. To avoid ambiguities, in this case the same
defaults section cannot be used by proxies with the frontend capability and
by proxies with the backend capability. It means a listen section cannot use
a defaults section defining such rules.
Note that the "if/unless" condition is optional. If no condition is set on
the action, it is simply performed unconditionally. That can be useful for
for changing the default action to a reject.
Several types of actions are supported :
It is perfectly possible to match layer 7 contents with "tcp-response
content" rules, but then it is important to ensure that a full response has
been buffered, otherwise no contents will match. In order to achieve this,
the best solution involves detecting the HTTP protocol during the inspection
period.
See
section 7 about ACL usage.
Set the maximum allowed time to wait for a response during content inspection
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
This directive is only available from named defaults sections, not anonymous
ones. Proxies inherit this value from their defaults section.
Set additional check timeout, but only after a connection has been already
established.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments:<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
If set, HAProxy uses min("
timeout connect", "
inter") as a connect timeout
for check and "
timeout check" as an additional read timeout. The "min" is
used so that people running with *very* long "
timeout connect" (e.g. those
who needed this due to the queue or tarpit) do not slow down their checks.
(Please also note that there is no valid reason to have such long connect
timeouts, because "
timeout queue" and "
timeout tarpit" can always be used to
avoid that).
If "
timeout check" is not set HAProxy uses "
inter" for complete check
timeout (connect + read) exactly like all <1.3.15 version.
In most cases check request is much simpler and faster to handle than normal
requests and people may want to kick out laggy servers so this timeout should
be smaller than "
timeout server".
This parameter is specific to backends, but can be specified once for all in
"defaults" sections. This is in fact one of the easiest solutions not to
forget about it.
Set the maximum inactivity time on the client side.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The inactivity timeout applies when the client is expected to acknowledge or
send data. In HTTP mode, this timeout is particularly important to consider
during the first phase, when the client sends the request, and during the
response while it is reading data sent by the server. That said, for the
first phase, it is preferable to set the "
timeout http-request" to better
protect HAProxy from Slowloris like attacks. The value is specified in
milliseconds by default, but can be in any other unit if the number is
suffixed by the unit, as specified at the top of this document. In TCP mode
(and to a lesser extent, in HTTP mode), it is highly recommended that the
client timeout remains equal to the server timeout in order to avoid complex
situations to debug. It is a good practice to cover one or several TCP packet
losses by specifying timeouts that are slightly above multiples of 3 seconds
(e.g. 4 or 5 seconds). If some long-lived streams are mixed with short-lived
streams (e.g. WebSocket and HTTP), it's worth considering "
timeout tunnel",
which overrides "
timeout client" and "
timeout server" for tunnels, as well as
"
timeout client-fin" for half-closed connections.
This parameter is specific to frontends, but can be specified once for all in
"defaults" sections. This is in fact one of the easiest solutions not to
forget about it. An unspecified timeout results in an infinite timeout, which
is not recommended. Such a usage is accepted and works but reports a warning
during startup because it may result in accumulation of expired sessions in
the system if the system's timeouts are not configured either.
Set the inactivity timeout on the client side for half-closed connections.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The inactivity timeout applies when the client is expected to acknowledge or
send data while one direction is already shut down. This timeout is different
from "
timeout client" in that it only applies to connections which are closed
in one direction. This is particularly useful to avoid keeping connections in
FIN_WAIT state for too long when clients do not disconnect cleanly. This
problem is particularly common long connections such as RDP or WebSocket.
Note that this timeout can override "
timeout tunnel" when a connection shuts
down in one direction. It is applied to idle HTTP/2 connections once a GOAWAY
frame was sent, often indicating an expectation that the connection quickly
ends.
This parameter is specific to frontends, but can be specified once for all in
"defaults" sections. By default it is not set, so half-closed connections
will use the other timeouts (timeout.client or timeout.tunnel).
Set the maximum time to wait for a client TLS handshake to complete. This is
usable both for TCP and QUIC connections.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
If this handshake timeout is not set, this is the client timeout which is used
in place.
Set the maximum time to wait for a connection attempt to a server to succeed.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
If the server is located on the same LAN as HAProxy, the connection should be
immediate (less than a few milliseconds). Anyway, it is a good practice to
cover one or several TCP packet losses by specifying timeouts that are
slightly above multiples of 3 seconds (e.g. 4 or 5 seconds). By default, the
connect timeout also presets both queue and tarpit timeouts to the same value
if these have not been specified.
This parameter is specific to backends, but can be specified once for all in
"defaults" sections. This is in fact one of the easiest solutions not to
forget about it. An unspecified timeout results in an infinite timeout, which
is not recommended. Such a usage is accepted and works but reports a warning
during startup because it may result in accumulation of failed sessions in
the system if the system's timeouts are not configured either.
Set the maximum allowed time to wait for a new HTTP request to appear
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
By default, the time to wait for a new request in case of keep-alive is set
by "
timeout http-request". However this is not always convenient because some
people want very short keep-alive timeouts in order to release connections
faster, and others prefer to have larger ones but still have short timeouts
once the request has started to present itself.
The "
http-keep-alive" timeout covers these needs. It will define how long to
wait for a new HTTP request to start coming after a response was sent. Once
the first byte of request has been seen, the "
http-request" timeout is used
to wait for the complete request to come. Note that empty lines prior to a
new request do not refresh the timeout and are not counted as a new request.
There is also another difference between the two timeouts : when a connection
expires during timeout http-keep-alive, no error is returned, the connection
just closes. If the connection expires in "
http-request" while waiting for a
request to complete, an HTTP 408 error is returned to the client before
closing the connection, unless "
option http-ignore-probes" is set in the
frontend.
In general "
timeout http-keep-alive" is best used to prevent clients from
holding open an otherwise idle connection too long on sites seeing large
amounts of short connections. This can be accomplished by setting the value
to a few tens to hundreds of milliseconds in HTTP/1.1. This will close the
connection after the client requests a page without having to hold that
connection open to wait for more activity from the client. In that scenario,
a new activity from the browser would result in a new handshake at the TCP
and/or SSL layer. A common use case for this is HTTP sites serving only a
redirect to the HTTPS page. Such connections are better not kept idle too
long because they won't be reused, unless maybe to fetch a favicon.
Another use case is the exact opposite: some sites want to permit clients
to reuse idle connections for a long time (e.g. 30 seconds to one minute) but
do not want to wait that long for the first request, in order to avoid a very
inexpensive attack vector. In this case, the http-keep-alive timeout would be
set to a large value, but http-request would remain low (a few seconds).
When set to a very small value additional requests that are not pipelined
are likely going to be handled over another connection unless the requests
are truly pipelined, which is very rare with HTTP/1.1 (requests being sent
back-to-back without waiting for a response). Most HTTP/1.1 implementations
send a request, wait for a response and then send another request. A small
value here for HTTP/1.1 may be advantageous to use less memory and sockets
for sites with hundreds of thousands of clients, at the expense of an
increase in handshake computation costs.
Special care should be taken with small values when dealing with HTTP/2. The
nature of HTTP/2 is to multiplex requests over a connection in order to save
on the overhead of reconnecting the TCP and/or SSL layers. The protocol also
uses control frames which cope poorly with early TCP connection closures, on
very rare occasions this may result in truncated responses when data are
destroyed in flight after leaving HAProxy (which then cannot even log an
error). A suggested low starting value for HTTP/2 connections would be around
4 seconds. This would prevent most modern keep-alive implementations from
needlessly holding open stale connections, and at the same time would allow
subsequent requests to reuse the connection. However, this should be adjusted
as needed and is simply a starting point.
If this parameter is not set, the "
http-request" timeout applies, and if both
are not set, "
timeout client" still applies at the lower level. It should be
set in the frontend to take effect, unless the frontend is in TCP mode, in
which case the HTTP backend's timeout will be used.
Set the maximum allowed time to wait for a complete HTTP request
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
In order to offer DoS protection, it may be required to lower the maximum
accepted time to receive a complete HTTP request without affecting the client
timeout. This helps protecting against established connections on which
nothing is sent. The client timeout cannot offer a good protection against
this abuse because it is an inactivity timeout, which means that if the
attacker sends one character every now and then, the timeout will not
trigger. With the HTTP request timeout, no matter what speed the client
types, the request will be aborted if it does not complete in time. When the
timeout expires, an HTTP 408 response is sent to the client to inform it
about the problem, and the connection is closed. The logs will report
termination codes "cR". Some recent browsers are having problems with this
standard, well-documented behavior, so it might be needed to hide the 408
code using "
option http-ignore-probes" or "errorfile 408 /dev/null". See
more details in the explanations of the "cR" termination code in
section 8.5.
By default, this timeout only applies to the header part of the request,
and not to any data. As soon as the empty line is received, this timeout is
not used anymore. When combined with "
option http-buffer-request", this
timeout also applies to the body of the request..
It is used again on keep-alive connections to wait for a second
request if "
timeout http-keep-alive" is not set.
Generally it is enough to set it to a few seconds, as most clients send the
full request immediately upon connection. Add 3 or more seconds to cover TCP
retransmits but that's all. Setting it to very low values (e.g. 50 ms) will
generally work on local networks as long as there are no packet losses. This
will prevent people from sending bare HTTP requests using telnet.
If this parameter is not set, the client timeout still applies between each
chunk of the incoming request. It should be set in the frontend to take
effect, unless the frontend is in TCP mode, in which case the HTTP backend's
timeout will be used.
Set the maximum time to wait in the queue for a connection slot to be free
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
When a server's maxconn is reached, connections are left pending in a queue
which may be server-specific or global to the backend. In order not to wait
indefinitely, a timeout is applied to requests pending in the queue. If the
timeout is reached, it is considered that the request will almost never be
served, so it is dropped and a 503 error is returned to the client.
The "
timeout queue" statement allows to fix the maximum time for a request to
be left pending in a queue. If unspecified, the same value as the backend's
connection timeout ("
timeout connect") is used, for backwards compatibility
with older versions with no "
timeout queue" parameter.
Set the maximum inactivity time on the server side.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The inactivity timeout applies when the server is expected to acknowledge or
send data. In HTTP mode, this timeout is particularly important to consider
during the first phase of the server's response, when it has to send the
headers, as it directly represents the server's processing time for the
request. To find out what value to put there, it's often good to start with
what would be considered as unacceptable response times, then check the logs
to observe the response time distribution, and adjust the value accordingly.
The value is specified in milliseconds by default, but can be in any other
unit if the number is suffixed by the unit, as specified at the top of this
document. In TCP mode (and to a lesser extent, in HTTP mode), it is highly
recommended that the client timeout remains equal to the server timeout in
order to avoid complex situations to debug. Whatever the expected server
response times, it is a good practice to cover at least one or several TCP
packet losses by specifying timeouts that are slightly above multiples of 3
seconds (e.g. 4 or 5 seconds minimum). If some long-lived streams are mixed
with short-lived streams (e.g. WebSocket and HTTP), it's worth considering
"
timeout tunnel", which overrides "
timeout client" and "
timeout server" for
tunnels.
This parameter is specific to backends, but can be specified once for all in
"defaults" sections. This is in fact one of the easiest solutions not to
forget about it. An unspecified timeout results in an infinite timeout, which
is not recommended. Such a usage is accepted and works but reports a warning
during startup because it may result in accumulation of expired sessions in
the system if the system's timeouts are not configured either.
Set the inactivity timeout on the server side for half-closed connections.
May be used in the following contexts: tcp, http, log
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The inactivity timeout applies when the server is expected to acknowledge or
send data while one direction is already shut down. This timeout is different
from "
timeout server" in that it only applies to connections which are closed
in one direction. This is particularly useful to avoid keeping connections in
FIN_WAIT state for too long when a remote server does not disconnect cleanly.
This problem is particularly common long connections such as RDP or WebSocket.
Note that this timeout can override "
timeout tunnel" when a connection shuts
down in one direction. This setting was provided for completeness, but in most
situations, it should not be needed.
This parameter is specific to backends, but can be specified once for all in
"defaults" sections. By default it is not set, so half-closed connections
will use the other timeouts (timeout.server or timeout.tunnel).
Set the duration for which tarpitted connections will be maintained
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the tarpit duration specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
When a connection is tarpitted using "http-request tarpit", it is maintained
open with no activity for a certain amount of time, then closed. "timeout
tarpit" defines how long it will be maintained open.
The value is specified in milliseconds by default, but can be in any other
unit if the number is suffixed by the unit, as specified at the top of this
document. If unspecified, the same value as the backend's connection timeout
("
timeout connect") is used, for backwards compatibility with older versions
with no "
timeout tarpit" parameter.
Set the maximum inactivity time on the client and server side for tunnels.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
The tunnel timeout applies when a bidirectional connection is established
between a client and a server, and the connection remains inactive in both
directions. This timeout supersedes both the client and server timeouts once
the connection becomes a tunnel. In TCP, this timeout is used as soon as no
analyzer remains attached to either connection (e.g. tcp content rules are
accepted). In HTTP, this timeout is used when a connection is upgraded (e.g.
when switching to the WebSocket protocol, or forwarding a CONNECT request
to a proxy), or after the first response when no keepalive/close option is
specified.
Since this timeout is usually used in conjunction with long-lived connections,
it usually is a good idea to also set "
timeout client-fin" to handle the
situation where a client suddenly disappears from the net and does not
acknowledge a close, or sends a shutdown and does not acknowledge pending
data anymore. This can happen in lossy networks where firewalls are present,
and is detected by the presence of large amounts of sessions in a FIN_WAIT
state.
The value is specified in milliseconds by default, but can be in any other
unit if the number is suffixed by the unit, as specified at the top of this
document. Whatever the expected normal idle time, it is a good practice to
cover at least one or several TCP packet losses by specifying timeouts that
are slightly above multiples of 3 seconds (e.g. 4 or 5 seconds minimum).
This parameter is specific to backends, but can be specified once for all in
"defaults" sections. This is in fact one of the easiest solutions not to
forget about it.
Example :
defaults http
option http-server-close
timeout connect 5s
timeout client 30s
timeout client-fin 30s
timeout server 30s
timeout tunnel 1h
Enable client-side transparent proxying
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments : none
This keyword was introduced in order to provide layer 7 persistence to layer
3 load balancers. The idea is to use the OS's ability to redirect an incoming
connection for a remote address to a local process (here HAProxy), and let
this process know what address was initially requested. When this option is
used, sessions without cookies will be forwarded to the original destination
IP address of the incoming request (which should match that of another
equipment), while requests with cookies will still be forwarded to the
appropriate server.
The "
transparent" keyword is deprecated, use "
option transparent" instead.
Note that contrary to a common belief, this option does NOT make HAProxy
present the client's IP to the server when establishing the connection.
Generate a unique ID for each request.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<string> is a log-format string.
This keyword creates a ID for each request using the custom log format. A
unique ID is useful to trace a request passing through many components of
a complex infrastructure. The newly created ID may also be logged using the
%ID tag the log-format string.
The format should be composed from elements that are guaranteed to be
unique when combined together. For instance, if multiple HAProxy instances
are involved, it might be important to include the node name. It is often
needed to log the incoming connection's source and destination addresses
and ports. Note that since multiple requests may be performed over the same
connection, including a request counter may help differentiate them.
Similarly, a timestamp may protect against a rollover of the counter.
Logging the process ID will avoid collisions after a service restart.
It is recommended to use hexadecimal notation for many fields since it
makes them more compact and saves space in logs.
Example:
unique-id-format %{+X}o\ %ci:%cp_%fi:%fp_%Ts_%rt:%pid
will generate:
7F000001:8296_7F00001E:1F90_4F7B0A69_0003:790A
Add a unique ID header in the HTTP request.
May be used in the following contexts: http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the name of the header.
Add a unique-id header in the HTTP request sent to the server, using the
unique-id-format. It can't work if the unique-id-format doesn't exist.
Example:
unique-id-format %{+X}o\ %ci:%cp_%fi:%fp_%Ts_%rt:%pid
unique-id-header X-Unique-ID
will generate:
X-Unique-ID: 7F000001:8296_7F00001E:1F90_4F7B0A69_0003:790A
See also: "unique-id-format"
Switch to a specific backend if/unless an ACL-based condition is matched.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<backend> is the name of a valid backend or "listen" section, or a
"log-format" string resolving to a backend name.
<condition> is a condition composed of ACLs, as described in section 7. If
it is omitted, the rule is unconditionally applied.
When doing content-switching, connections arrive on a frontend and are then
dispatched to various backends depending on a number of conditions. The
relation between the conditions and the backends is described with the
"
use_backend" keyword. While it is normally used with HTTP processing, it can
also be used in pure TCP, either without content using stateless ACLs (e.g.
source address validation) or combined with a "
tcp-request" rule to wait for
some payload.
There may be as many "
use_backend" rules as desired. All of these rules are
evaluated in their declaration order, and the first one which matches will
assign the backend.
In the first form, the backend will be used if the condition is met. In the
second form, the backend will be used if the condition is not met. If no
condition is valid, the backend defined with "
default_backend" will be used.
If no default backend is defined, either the servers in the same section are
used (in case of a "listen" section) or, in case of a frontend, no server is
used and a 503 service unavailable response is returned.
Note that it is possible to switch from a TCP frontend to an HTTP backend. In
this case, either the frontend has already checked that the protocol is HTTP,
and backend processing will immediately follow, or the backend will wait for
a complete HTTP request to get in. This feature is useful when a frontend
must decode several protocols on a unique port, one of them being HTTP.
When <backend> is a simple name, it is resolved at configuration time, and an
error is reported if the specified backend does not exist. If <backend> is
a log-format string instead, no check may be done at configuration time, so
the backend name is resolved dynamically at run time. If the resulting
backend name does not correspond to any valid backend, no other rule is
evaluated, and the default_backend directive is applied instead. Note that
when using dynamic backend names, it is highly recommended to use a prefix
that no other backend uses in order to ensure that an unauthorized backend
cannot be forced from the request.
It is worth mentioning that "
use_backend" rules with an explicit name are
used to detect the association between frontends and backends to compute the
backend's "
fullconn" setting. This cannot be done for dynamic names.
Defines the FastCGI application to use for the backend.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<name> is the name of the FastCGI application to use.
See
section 10.1 about FastCGI application setup for details.
Only use a specific server if/unless an ACL-based condition is matched.
May be used in the following contexts: tcp, http
May be used in sections :
defaults | frontend | listen | backend |
Arguments :<server> is the name of a valid server in the same backend section
or a "log-format" string resolving to a server name.
<condition> is a condition composed of ACLs, as described in section 7.
By default, connections which arrive to a backend are load-balanced across
the available servers according to the configured algorithm, unless a
persistence mechanism such as a cookie is used and found in the request.
Sometimes it is desirable to forward a particular request to a specific
server without having to declare a dedicated backend for this server. This
can be achieved using the "
use-server" rules. These rules are evaluated after
the "
redirect" rules and before evaluating cookies, and they have precedence
on them. There may be as many "
use-server" rules as desired. All of these
rules are evaluated in their declaration order, and the first one which
matches will assign the server.
If a rule designates a server which is down, and "
option persist" is not used
and no force-persist rule was validated, it is ignored and evaluation goes on
with the next rules until one matches.
In the first form, the server will be used if the condition is met. In the
second form, the server will be used if the condition is not met. If no
condition is valid, the processing continues and the server will be assigned
according to other persistence mechanisms.
Note that even if a rule is matched, cookie processing is still performed but
does not assign the server. This allows prefixed cookies to have their prefix
stripped.
The "
use-server" statement works both in HTTP and TCP mode. This makes it
suitable for use with content-based inspection. For instance, a server could
be selected in a farm according to the TLS SNI field when using protocols with
implicit TLS (also see "
req.ssl_sni"). And if these servers have their weight
set to zero, they will not be used for other traffic.
Example :
use-server www if { req.ssl_sni -i www.example.com }
server www 192.168.0.1:443 weight 0
use-server mail if { req.ssl_sni -i mail.example.com }
server mail 192.168.0.1:465 weight 0
use-server imap if { req.ssl_sni -i imap.example.com }
server imap 192.168.0.1:993 weight 0
server default 192.168.0.2:443 check
When <server> is a simple name, it is checked against existing servers in the
configuration and an error is reported if the specified server does not exist.
If it is a log-format, no check is performed when parsing the configuration,
and if we can't resolve a valid server name at runtime but the use-server rule
was conditioned by an ACL returning true, no other use-server rule is applied
and we fall back to load balancing.
Sample fetch methods may be combined with transformations to be applied on top
of the fetched sample (also called "converters"). These combinations form what
is called "sample expressions" and the result is a "sample". Initially this
was only supported by "
stick on" and "
stick store-request" directives but this
has now be extended to all places where samples may be used (ACLs, log-format,
unique-id-format, add-header, ...).
These transformations are enumerated as a series of specific keywords after the
sample fetch method. These keywords may equally be appended immediately after
the fetch keyword's argument, delimited by a comma. These keywords can also
support some arguments (e.g. a netmask) which must be passed in parenthesis.
A certain category of converters are bitwise and arithmetic operators which
support performing basic operations on integers. Some bitwise operations are
supported (and, or, xor, cpl) and some arithmetic operations are supported
(add, sub, mul, div, mod, neg). Some comparators are provided (odd, even, not,
bool) which make it possible to report a match without having to write an ACL.
The following keywords are supported:
keyword | input type | output type |
51d.single(prop[,prop*]) | string | string |
add(value) | integer | integer |
add_item(delim,[var][,suff]]) | string | string |
aes_gcm_dec(bits,nonce,key,aead_tag) | binary | binary |
and(value) | integer | integer |
b64dec | string | binary |
base64 | binary | string |
be2dec(separator,chunk_size,[truncate]) | binary | string |
be2hex([separator],[chunk_size],[truncate]) | binary | string |
bool | integer | boolean |
bytes(offset[,length]) | binary | binary |
capture-req(id) | string | string |
capture-res(id) | string | string |
concat([start],[var],[end]) | string | string |
cpl | integer | integer |
crc32([avalanche]) | binary | integer |
crc32c([avalanche]) | binary | integer |
cut_crlf | string | string |
da-csv-conv(prop[,prop*]) | string | string |
debug([prefix][,destination]) | any | same |
keyword | input type | output type |
digest(algorithm) | binary | binary |
div(value) | integer | integer |
djb2([avalanche]) | binary | integer |
even | integer | boolean |
field(index,delimiters[,count]) | string | string |
fix_is_valid | binary | boolean |
fix_tag_value(tag) | binary | binary |
hex | binary | string |
hex2i | binary | integer |
hmac(algorithm,key) | binary | binary |
host_only | string | string |
htonl | integer | integer |
http_date([offset],[unit]) | integer | string |
iif(true,false) | boolean | string |
in_table(table) | string | boolean |
ipmask(mask4,[mask6]) | address | address |
json([input-code]) | string | string |
json_query(json_path,[output_type]) | string | _outtype_ |
jwt_header_query([json_path],[output_type]) | string | string |
jwt_payload_query([json_path],[output_type]) | string | string |
keyword | input type | output type |
jwt_verify(alg,key) | string | integer |
language(value[,default]) | string | string |
length | string | integer |
lower | string | string |
ltime(format[,offset]) | integer | string |
ltrim(chars) | string | string |
map(map_name[,default_value]) | string | string |
map_match(map_name[,default_value]) | _match_ | string |
map_match_output(map_name[,default_value]) | _match_ | _output_ |
mod(value) | integer | integer |
mqtt_field_value(pkt_type,fieldname_or_prop_ID) | binary | binary |
mqtt_is_valid | binary | boolean |
ms_ltime(format[,offset]) | integer | string |
ms_utime(format[,offset]) | integer | string |
mul(value) | integer | integer |
nbsrv | string | integer |
neg | integer | integer |
not | integer | boolean |
odd | integer | boolean |
or(value) | integer | integer |
keyword | input type | output type |
param(name,[delim]) | string | string |
port_only | string | integer |
protobuf(field_number,[field_type]) | binary | binary |
regsub(regex,subst[,flags]) | string | string |
rfc7239_field(field) | string | string |
rfc7239_is_valid | string | boolean |
rfc7239_n2nn | string | address / str |
rfc7239_n2np | string | integer / str |
rtrim(chars) | string | string |
sdbm([avalanche]) | binary | integer |
secure_memcmp(var) | string | boolean |
set-var(var[,cond...]) | any | same |
sha1 | binary | binary |
sha2([bits]) | binary | binary |
srv_queue | string | integer |
strcmp(var) | string | boolean |
sub(value) | integer | integer |
table_bytes_in_rate(table) | string | integer |
table_bytes_out_rate(table) | string | integer |
table_conn_cnt(table) | string | integer |
keyword | input type | output type |
table_conn_cur(table) | string | integer |
table_conn_rate(table) | string | integer |
table_expire(table[,default_value]) | string | integer |
table_gpc(idx,table) | string | integer |
table_gpc0(table) | string | integer |
table_gpc0_rate(table) | string | integer |
table_gpc1(table) | string | integer |
table_gpc1_rate(table) | string | integer |
table_gpc_rate(idx,table) | string | integer |
table_gpt(idx,table) | string | integer |
table_gpt0(table) | string | integer |
table_gptstr(...) | string | string |
table_http_err_cnt(table) | string | integer |
table_http_err_rate(table) | string | integer |
table_http_fail_cnt(table) | string | integer |
table_http_fail_rate(table) | string | integer |
table_http_req_cnt(table) | string | integer |
table_http_req_rate(table) | string | integer |
table_idle(table[,default_value]) | string | integer |
table_kbytes_in(table) | string | integer |
keyword | input type | output type |
table_kbytes_out(table) | string | integer |
table_server_id(table) | string | integer |
table_sess_cnt(table) | string | integer |
table_sess_rate(table) | string | integer |
table_trackers(table) | string | integer |
ub64dec | string | string |
ub64enc | string | string |
ungrpc(field_number,[field_type]) | binary | binary / int |
unset-var(var) | any | same |
upper | string | string |
url_dec([in_form]) | string | string |
url_enc([enc_type]) | string | string |
us_ltime(format[,offset]) | integer | string |
us_utime(format[,offset]) | integer | string |
utime(format[,offset]) | integer | string |
word(index,delimiters[,count]) | string | string |
wt6([avalanche]) | binary | integer |
x509_v_err_str | integer | string |
xor(value) | integer | integer |
xxh3([seed]) | binary | integer |
keyword | input type | output type |
xxh32([seed]) | binary | integer |
The detailed list of converter keywords follows:
Returns values for the properties requested as a string, where values are
separated by the delimiter specified with "
51degrees-property-separator".
The device is identified using the User-Agent header passed to the
converter. The function can be passed up to five property names, and if a
property name can't be found, the value "NoData" is returned.
Example :
frontend http-in
bind *:8081
default_backend servers
http-request set-header X-51D-DeviceTypeMobileTablet \
%[req.fhdr(User-Agent),51d.single(DeviceType,IsMobile,IsTablet)]
Adds <value> to the input value of type signed integer, and returns the
result as a signed integer. <value> can be a numeric value or a variable
name. The name of the variable starts with an indication about its scope. The
scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and response)
"req" : the variable is shared only during request processing
"res" : the variable is shared only during response processing
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
Concatenates a minimum of 2 and up to 3 fields after the current sample which
is then turned into a string. The first one, <delim>, is a constant string,
that will be appended immediately after the existing sample if an existing
sample is not empty and either the <var> or the <suff> is not empty. The
second one, <var>, is a variable name. The variable will be looked up, its
contents converted to a string, and it will be appended immediately after
the <delim> part. If the variable is not found, nothing is appended. It is
optional and may optionally be followed by a constant string <suff>, however
if <var> is omitted, then <suff> is mandatory. This converter is similar to
the concat converter and can be used to build new variables made of a
succession of other variables but the main difference is that it does the
checks if adding a delimiter makes sense as wouldn't be the case if e.g. the
current sample is empty. That situation would require 2 separate rules using
concat converter where the first rule would have to check if the current
sample string is empty before adding a delimiter. If commas or closing
parenthesis are needed as delimiters, they must be protected by quotes or
backslashes, themselves protected so that they are not stripped by the first
level parser (please see
section 2.2 for quoting and escaping). See examples
below.
Example:
http-request set-var(req.tagged) 'var(req.tagged),add_item(",",req.score1,"(site1)") if src,in_table(site1)'
http-request set-var(req.tagged) 'var(req.tagged),add_item(",",req.score2,"(site2)") if src,in_table(site2)'
http-request set-var(req.tagged) 'var(req.tagged),add_item(",",req.score3,"(site3)") if src,in_table(site3)'
http-request set-header x-tagged %[var(req.tagged)]
http-request set-var(req.tagged) 'var(req.tagged),add_item(",",req.score1),add_item(",",req.score2)'
http-request set-var(req.tagged) 'var(req.tagged),add_item(",",,(site1))' if src,in_table(site1)
Decrypts the raw byte input using the AES128-GCM, AES192-GCM or
AES256-GCM algorithm, depending on the <bits> parameter. All other parameters
need to be base64 encoded and the returned result is in raw byte format.
If the <aead_tag> validation fails, the converter doesn't return any data.
The <nonce>, <key> and <aead_tag> can either be strings or variables. This
converter requires at least OpenSSL 1.0.1.
Example:
http-response set-header X-Decrypted-Text %[var(txn.enc),\
aes_gcm_dec(128,txn.nonce,Zm9vb2Zvb29mb29wZm9vbw==,txn.aead_tag)]
Performs a bitwise "AND" between <value> and the input value of type signed
integer, and returns the result as an signed integer. <value> can be a
numeric value or a variable name. The name of the variable starts with an
indication about its scope. The scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and response)
"req" : the variable is shared only during request processing
"res" : the variable is shared only during response processing
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
Converts (decodes) a base64 encoded input string to its binary
representation. It performs the inverse operation of base64().
For base64url("URL and Filename Safe Alphabet" (RFC 4648)) variant
see "
ub64dec".
Converts a binary input sample to a base64 string. It is used to log or
transfer binary content in a way that can be reliably transferred (e.g.
an SSL ID can be copied in a header). For base64url("URL and Filename
Safe Alphabet" (RFC 4648)) variant see "
ub64enc".
be2dec(
<separator>,
<chunk_size>,
[<truncate>])
Converts big-endian binary input sample to a string containing an unsigned
integer number per <chunk_size> input bytes. <separator> is put every
<chunk_size> binary input bytes if specified. <truncate> flag indicates
whatever binary input is truncated at <chunk_size> boundaries. <chunk_size>
maximum value is limited by the size of long long int (8 bytes).
Example:
bin(01020304050607),be2dec(:,2)
bin(01020304050607),be2dec(-,2,1)
bin(01020304050607),be2dec(,2,1)
bin(7f000001),be2dec(.,1)
be2hex(
[<separator>],
[<chunk_size>],
[<truncate>])
Converts big-endian binary input sample to a hex string containing two hex
digits per input byte. It is used to log or transfer hex dumps of some
binary input data in a way that can be reliably transferred (e.g. an SSL ID
can be copied in a header). <separator> is put every <chunk_size> binary
input bytes if specified. <truncate> flag indicates whatever binary input is
truncated at <chunk_size> boundaries.
Example:
bin(01020304050607),be2hex
bin(01020304050607),be2hex(:,2)
bin(01020304050607),be2hex(--,2,1)
bin(0102030405060708),be2hex(,3,1)
Returns a boolean TRUE if the input value of type signed integer is
non-null, otherwise returns FALSE. Used in conjunction with and(), it can be
used to report true/false for bit testing on input values (e.g. verify the
presence of a flag).
bytes(
<offset>[,<length>])
Extracts some bytes from an input binary sample. The result is a binary
sample starting at an offset (in bytes) of the original sample and
optionally truncated at the given length. <offset> and <length> can be numeric
values or variable names. The converter returns an empty sample if either
<offset> or <length> is invalid. Invalid <offset> means a negative value or a
value >= length of the input sample. Invalid <length> means a negative value
or, in some cases, a value bigger than the length of the input sample.
Example:
http-request set-var(txn.input) req.hdr(input)
http-response set-header bytes_0 "%[var(txn.input),bytes(0)]"
http-response set-header bytes_1_3 "%[var(txn.input),bytes(1,3)]"
http-response set-var(txn.var_start) int(1)
http-response set-var(txn.var_length) int(3)
http-response set-header bytes_var1_var3 "%[var(txn.input),bytes(txn.var_start,txn.var_length)]"
Capture the string entry in the request slot <id> and returns the entry as
is. If the slot doesn't exist, the capture fails silently.
Capture the string entry in the response slot <id> and returns the entry as
is. If the slot doesn't exist, the capture fails silently.
concat(
[<start>],
[<var>],
[<end>])
Concatenates up to 3 fields after the current sample which is then turned to
a string. The first one, <start>, is a constant string, that will be appended
immediately after the existing sample. It may be omitted if not used. The
second one, <var>, is a variable name. The variable will be looked up, its
contents converted to a string, and it will be appended immediately after the
<first> part. If the variable is not found, nothing is appended. It may be
omitted as well. The third field, <end> is a constant string that will be
appended after the variable. It may also be omitted. Together, these elements
allow to concatenate variables with delimiters to an existing set of
variables. This can be used to build new variables made of a succession of
other variables, such as colon-delimited values. If commas or closing
parenthesis are needed as delimiters, they must be protected by quotes or
backslashes, themselves protected so that they are not stripped by the first
level parser. This is often used to build composite variables from other
ones, but sometimes using a format string with multiple fields may be more
convenient. See examples below.
Example:
tcp-request session set-var(sess.src) src
tcp-request session set-var(sess.dn) ssl_c_s_dn
tcp-request session set-var(txn.sig) str(),concat(<ip=,sess.ip,>),concat(<dn=,sess.dn,>)
tcp-request session set-var(txn.ipport) "str(),concat('addr=(',sess.ip),concat(',',sess.port,')')"
tcp-request session set-var-fmt(txn.ipport) "addr=(%[sess.ip],%[sess.port])"
http-request set-header x-hap-sig %[var(txn.sig)]
Takes the input value of type signed integer, applies a ones-complement
(flips all bits) and returns the result as an signed integer.
Hashes a binary input sample into an unsigned 32-bit quantity using the CRC32
hash function. Optionally, it is possible to apply a full avalanche hash
function to the output if the optional <avalanche> argument equals 1. This
converter uses the same functions as used by the various hash-based load
balancing algorithms, so it will provide exactly the same results. It is
provided for compatibility with other software which want a CRC32 to be
computed on some input keys, so it follows the most common implementation as
found in Ethernet, Gzip, PNG, etc... It is slower than the other algorithms
but may provide a better or at least less predictable distribution. It must
not be used for security purposes as a 32-bit hash is trivial to break. See
also "
djb2", "
sdbm", "
wt6", "
crc32c" and the "
hash-type" directive.
Hashes a binary input sample into an unsigned 32-bit quantity using the CRC32C
hash function. Optionally, it is possible to apply a full avalanche hash
function to the output if the optional <avalanche> argument equals 1. This
converter uses the same functions as described in RFC4960, Appendix B [8].
It is provided for compatibility with other software which want a CRC32C to be
computed on some input keys. It is slower than the other algorithms and it must
not be used for security purposes as a 32-bit hash is trivial to break. See
also "
djb2", "
sdbm", "
wt6", "
crc32" and the "
hash-type" directive.
Cuts the string representation of the input sample on the first carriage
return ('\r') or newline ('\n') character found. Only the string length is
updated.
Asks the DeviceAtlas converter to identify the User Agent string passed on
input, and to emit a string made of the concatenation of the properties
enumerated in argument, delimited by the separator defined by the global
keyword "deviceatlas-property-separator", or by default the pipe character
('|'). There's a limit of 12 different properties imposed by the HAProxy
configuration language.
Example:
frontend www
bind *:8881
default_backend servers
http-request set-header X-DeviceAtlas-Data %[req.fhdr(User-Agent),da-csv(primaryHardwareType,osName,osVersion,browserName,browserVersion,browserRenderingEngine)]
debug(
[<prefix][,<destination>])
This converter is used as debug tool. It takes a capture of the input sample
and sends it to event sink <destination>, which may designate a ring buffer
such as "buf0", as well as "stdout", or "stderr". Available sinks may be
checked at run time by issuing "show events" on the CLI. When not specified,
the output will be "buf0", which may be consulted via the CLI's "show events"
command. An optional prefix <prefix> may be passed to help distinguish
outputs from multiple expressions. It will then appear before the colon in
the output message. The input sample is passed as-is on the output, so that
it is safe to insert the debug converter anywhere in a chain, even with non-
printable sample types.
Example:
tcp-request connection track-sc0 src,debug(track-sc)
Converts a binary input sample to a message digest. The result is a binary
sample. The <algorithm> must be an OpenSSL message digest name (e.g. sha256).
Please note that this converter is only available when HAProxy has been
compiled with USE_OPENSSL.
Divides the input value of type signed integer by <value>, and returns the
result as an signed integer. If <value> is null, the largest unsigned
integer is returned (typically 2^63-1). <value> can be a numeric value or a
variable name. The name of the variable starts with an indication about its
scope. The scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and response)
"req" : the variable is shared only during request processing
"res" : the variable is shared only during response processing
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
Hashes a binary input sample into an unsigned 32-bit quantity using the DJB2
hash function. Optionally, it is possible to apply a full avalanche hash
function to the output if the optional <avalanche> argument equals 1. This
converter uses the same functions as used by the various hash-based load
balancing algorithms, so it will provide exactly the same results. It is
mostly intended for debugging, but can be used as a stick-table entry to
collect rough statistics. It must not be used for security purposes as a
32-bit hash is trivial to break. See also "
crc32", "
sdbm", "
wt6", "
crc32c",
and the "
hash-type" directive.
Returns a boolean TRUE if the input value of type signed integer is even
otherwise returns FALSE. It is functionally equivalent to "not,and(1),bool".
field(
<index>,
<delimiters>[,<count>])
Extracts the substring at the given index counting from the beginning
(positive index) or from the end (negative index) considering given delimiters
from an input string. Indexes start at 1 or -1 and delimiters are a string
formatted list of chars. Optionally you can specify <count> of fields to
extract (default: 1). Value of 0 indicates extraction of all remaining
fields.
Example :
str(f1_f2_f3__f5),field(4,_)
str(f1_f2_f3__f5),field(5,_)
str(f1_f2_f3__f5),field(2,_,0)
str(f1_f2_f3__f5),field(2,_,2)
str(f1_f2_f3__f5),field(-2,_,3)
str(f1_f2_f3__f5),field(-3,_,0)
Parses a binary payload and performs sanity checks regarding FIX (Financial
Information eXchange):
- checks that all tag IDs and values are not empty and the tags IDs are well
numeric
- checks the BeginString tag is the first tag with a valid FIX version
- checks the BodyLength tag is the second one with the right body length
- checks the MsgType tag is the third tag.
- checks that last tag in the message is the CheckSum tag with a valid
checksum
Due to current HAProxy design, only the first message sent by the client and
the server can be parsed.
This converter returns a boolean, true if the payload contains a valid FIX
message, false if not.
See also the fix_tag_value converter.
Example:
tcp-request inspect-delay 10s
tcp-request content reject unless { req.payload(0,0),fix_is_valid }
Parses a FIX (Financial Information eXchange) message and extracts the value
from the tag <tag>. <tag> can be a string or an integer pointing to the
desired tag. Any integer value is accepted, but only the following strings
are translated into their integer equivalent: BeginString, BodyLength,
MsgType, SenderCompID, TargetCompID, CheckSum. More tag names can be easily
added.
Due to current HAProxy design, only the first message sent by the client and
the server can be parsed. No message validation is performed by this
converter. It is highly recommended to validate the message first using
fix_is_valid converter.
See also the fix_is_valid converter.
Example:
tcp-request inspect-delay 10s
tcp-request content reject unless { req.payload(0,0),fix_is_valid }
tcp-request content set-var(txn.foo) req.payload(0,0),fix_tag_value(35)
tcp-request content set-var(txn.bar) req.payload(0,0),fix_tag_value(MsgType)
Converts a binary input sample to a hex string containing two hex digits per
input byte. It is used to log or transfer hex dumps of some binary input data
in a way that can be reliably transferred (e.g. an SSL ID can be copied in a
header).
Converts a hex string containing two hex digits per input byte to an
integer. If the input value cannot be converted, then zero is returned.
Converts a binary input sample to a message authentication code with the given
key. The result is a binary sample. The <algorithm> must be one of the
registered OpenSSL message digest names (e.g. sha256). The <key> parameter must
be base64 encoded and can either be a string or a variable.
Please note that this converter is only available when HAProxy has been
compiled with USE_OPENSSL.
Converts a string which contains a Host header value and removes its port.
The input must respect the format of the host header value
(rfc9110#section-7.2). It will support that kind of input: hostname,
hostname:80, 127.0.0.1, 127.0.0.1:80, [::1], [::1]:80.
This converter also sets the string in lowercase.
Converts the input integer value to its 32-bit binary representation in the
network byte order. Because sample fetches own signed 64-bit integer, when
this converter is used, the input integer value is first casted to an
unsigned 32-bit integer.
Converts an integer supposed to contain a date since epoch to a string
representing this date in a format suitable for use in HTTP header fields. If
an offset value is specified, then it is added to the date before the
conversion is operated. This is particularly useful to emit Date header fields,
Expires values in responses when combined with a positive offset, or
Last-Modified values when the offset is negative.
If a unit value is specified, then consider the timestamp as either
"s" for seconds (default behavior), "ms" for milliseconds, or "us" for
microseconds since epoch. Offset is assumed to have the same unit as
input timestamp.
Returns the <true> string if the input value is true. Returns the <false>
string otherwise.
Example:
http-request set-header x-forwarded-proto %[ssl_fc,iif(https,http)]
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, a boolean false
is returned. Otherwise a boolean true is returned. This can be used to verify
the presence of a certain key in a table tracking some elements (e.g. whether
or not a source IP address or an Authorization header was already seen).
Apply a mask to an IP address, and use the result for lookups and storage.
This can be used to make all hosts within a certain mask to share the same
table entries and as such use the same server. The mask4 can be passed in
dotted form (e.g. 255.255.255.0) or in CIDR form (e.g. 24). The mask6 can
be passed in quadruplet form (e.g. ffff:ffff::) or in CIDR form (e.g. 64).
If no mask6 is given IPv6 addresses will fail to convert for backwards
compatibility reasons.
Escapes the input string and produces an ASCII output string ready to use as a
JSON string. The converter tries to decode the input string according to the
<input-code> parameter. It can be "ascii", "utf8", "utf8s", "utf8p" or
"utf8ps". The "ascii" decoder never fails. The "utf8" decoder detects 3 types
of errors:
- bad UTF-8 sequence (lone continuation byte, bad number of continuation
bytes, ...)
- invalid range (the decoded value is within a UTF-8 prohibited range),
- code overlong (the value is encoded with more bytes than necessary).
The UTF-8 JSON encoding can produce a "too long value" error when the UTF-8
character is greater than 0xffff because the JSON string escape specification
only authorizes 4 hex digits for the value encoding. The UTF-8 decoder exists
in 4 variants designated by a combination of two suffix letters : "p" for
"permissive" and "s" for "silently ignore". The behaviors of the decoders
are :
- "ascii" : never fails;
- "utf8" : fails on any detected errors;
- "utf8s" : never fails, but removes characters corresponding to errors;
- "utf8p" : accepts and fixes the overlong errors, but fails on any other
error;
- "utf8ps" : never fails, accepts and fixes the overlong errors, but removes
characters corresponding to the other errors.
This converter is particularly useful for building properly escaped JSON for
logging to servers which consume JSON-formatted traffic logs.
Example:
capture request header Host len 15
capture request header user-agent len 150
log-format '{"ip":"%[src]","user-agent":"%[capture.req.hdr(1),json(utf8s)]"}'
Input request from client 127.0.0.1:
GET / HTTP/1.0
User-Agent: Very "Ugly" UA 1/2
Output log:
{"ip":"127.0.0.1","user-agent":"Very \"Ugly\" UA 1\/2"}
The json_query converter supports the JSON types string, boolean, number
and array. Floating point numbers will be returned as a string. By
specifying the output_type 'int' the value will be converted to an
Integer. Arrays will be returned as string, starting and ending with a
square brackets. The content is a CSV. Depending on the data type, the
array values might be quoted. If the array values are complex types,
the string contains the complete json representation of each value
separated by a comma. Example result for a roles query to a JWT:
["manage-account","manage-account-links","view-profile"]
If conversion is not possible the json_query converter fails.
<json_path> must be a valid JSON Path string as defined in
https://datatracker.ietf.org/doc/draft-ietf-jsonpath-base/
Example:
http-request set-var(txn.pay_int) req.body,json_query('$.integer','int'),add(1)
http-request set-var(txn.pay_mykey) req.body,json_query('$.my\\.key')
http-request set-var(txn.pay_boolean_false) req.body,json_query('$.boolean-false')
http-request set-var(txn.token_payload) req.hdr(Authorization),word(2,.),ub64dec,json_query('$.iss')
When given a JSON Web Token (JWT) in input, either returns the decoded header
part of the token (the first base64-url encoded part of the JWT) if no
parameter is given, or performs a json_query on the decoded header part of
the token. See "
json_query" converter for details about the accepted
json_path and output_type parameters.
Please note that this converter is only available when HAProxy has been
compiled with USE_OPENSSL.
When given a JSON Web Token (JWT) in input, either returns the decoded
payload part of the token (the second base64-url encoded part of the JWT) if
no parameter is given, or performs a json_query on the decoded payload part
of the token. See "
json_query" converter for details about the accepted
json_path and output_type parameters.
Please note that this converter is only available when HAProxy has been
compiled with USE_OPENSSL.
Performs a signature verification for the JSON Web Token (JWT) given in input
by using the <alg> algorithm and the <key> parameter, which should either
hold a secret or a path to a public certificate. Returns 1 in case of
verification success, 0 in case of verification error and a strictly negative
value for any other error. Because of all those non-null error return values,
the result of this converter should never be converted to a boolean. See
below for a full list of the possible return values.
For now, only JWS tokens using the Compact Serialization format can be
processed (three dot-separated base64-url encoded strings). All the
algorithms mentioned in
section 3.1 of RFC7518 are managed (HS, ES, RS and PS
with the 256, 384 or 512 key sizes, as well as the special "none" case).
If the used algorithm is of the HMAC family, <key> should be the secret used
in the HMAC signature calculation. Otherwise, <key> should be the path to the
public certificate that can be used to validate the token's signature. All
the certificates that might be used to verify JWTs must be known during init
in order to be added into a dedicated certificate cache so that no disk
access is required during runtime. For this reason, any used certificate must
be mentioned explicitly at least once in a jwt_verify call. Passing an
intermediate variable as second parameter is then not advised.
This converter only verifies the signature of the token and does not perform
a full JWT validation as specified in
section 7.2 of RFC7519. We do not
ensure that the header and payload contents are fully valid JSON's once
decoded for instance, and no checks are performed regarding their respective
contents.
The possible return values are the following :
+----+----------------------------------------------------------------------+
| ID | message |
+----+----------------------------------------------------------------------+
| 0 | "Verification failure" |
| 1 | "Verification success" |
| -1 | "Unknown algorithm (not mentioned in RFC7518)" |
| -2 | "Unmanaged algorithm" |
| -3 | "Invalid token" |
| -4 | "Out of memory" |
| -5 | "Unknown certificate" |
+----+----------------------------------------------------------------------+
Please note that this converter is only available when HAProxy has been
compiled with USE_OPENSSL.
Example:
http-request set-var(txn.bearer) http_auth_bearer
http-request set-var(txn.jwt_alg) var(txn.bearer),jwt_header_query('$.alg')
http-request deny unless { var(txn.jwt_alg) -m str "RS256" }
http-request deny unless { var(txn.bearer),jwt_verify(txn.jwt_alg,"/path/to/crt.pem") 1 }
Returns the value with the highest q-factor from a list as extracted from the
"accept-language" header using "
req.fhdr". Values with no q-factor have a
q-factor of 1. Values with a q-factor of 0 are dropped. Only values which
belong to the list of semi-colon delimited <values> will be considered. The
argument <value> syntax is "lang[;lang[;lang[;...]]]". If no value matches the
given list and a default value is provided, it is returned. Note that language
names may have a variant after a dash ('-'). If this variant is present in the
list, it will be matched, but if it is not, only the base language is checked.
The match is case-sensitive, and the output string is always one of those
provided in arguments. The ordering of arguments is meaningless, only the
ordering of the values in the request counts, as the first value among
multiple sharing the same q-factor is used.
Example :
acl es req.fhdr(accept-language),language(es;fr;en) -m str es
acl fr req.fhdr(accept-language),language(es;fr;en) -m str fr
acl en req.fhdr(accept-language),language(es;fr;en) -m str en
use_backend spanish if es
use_backend french if fr
use_backend english if en
default_backend choose_your_language
Get the length of the string. This can only be placed after a string
sample fetch function or after a transformation keyword returning a string
type. The result is of type integer.
Convert a string sample to lower case. This can only be placed after a string
sample fetch function or after a transformation keyword returning a string
type. The result is of type string.
ltime(
<format>[,<offset>])
Converts an integer supposed to contain a date since epoch to a string
representing this date in local time using a format defined by the <format>
string using strftime(3). The purpose is to allow any date format to be used
in logs. An optional <offset> in seconds may be applied to the input date
(positive or negative). See the strftime() man page for the format supported
by your operating system. See also the utime converter.
Example :
log-format %[date,ltime(%Y%m%d%H%M%S)]\ %ci:%cp
Skips any characters from <chars> from the beginning of the string
representation of the input sample.
map(
<map_file>[,<default_value>])
map_<match_type>(<map_file>[,<default_value>])
map_<match_type>_<output_type>(<map_file>[,<default_value>])
Search the input value from <map_file> using the <match_type> matching method,
and return the associated value converted to the type <output_type>. If the
input value cannot be found in the <map_file>, the converter returns the
<default_value>. If the <default_value> is not set, the converter fails and
acts as if no input value could be fetched. If the <match_type> is not set, it
defaults to "
str". Likewise, if the <output_type> is not set, it defaults to
"
str". For convenience, the "
map" keyword is an alias for "map_str" and maps a
string to another string.
It is important to avoid overlapping between the keys : IP addresses and
strings are stored in trees, so the first of the finest match will be used.
Other keys are stored in lists, so the first matching occurrence will be used.
The following array contains the list of all map functions available sorted by
input type, match type and output type.
input type | match method | output type str | output type int | output type ip |
str | str | map_str | map_str_int | map_str_ip |
str | beg | map_beg | map_beg_int | map_end_ip |
str | sub | map_sub | map_sub_int | map_sub_ip |
str | dir | map_dir | map_dir_int | map_dir_ip |
str | dom | map_dom | map_dom_int | map_dom_ip |
str | end | map_end | map_end_int | map_end_ip |
str | reg | map_reg | map_reg_int | map_reg_ip |
str | reg | map_regm | map_reg_int | map_reg_ip |
int | int | map_int | map_int_int | map_int_ip |
ip | ip | map_ip | map_ip_int | map_ip_ip |
The special map called "map_regm" expect matching zone in the regular
expression and modify the output replacing back reference (like "\1") by
the corresponding match text.
The file contains one key + value per line. Lines which start with '#' are
ignored, just like empty lines. Leading tabs and spaces are stripped. The key
is then the first "
word" (series of non-space/tabs characters), and the value
is what follows this series of space/tab till the end of the line excluding
trailing spaces/tabs.
Example :
2.22.246.0/23 United Kingdom \n
<-><-----------><--><------------><---->
| | | | `- trailing spaces ignored
| | | `---------- value
| | `-------------------- middle spaces ignored
| `---------------------------- key
`------------------------------------ leading spaces ignored
Divides the input value of type signed integer by <value>, and returns the
remainder as an signed integer. If <value> is null, then zero is returned.
<value> can be a numeric value or a variable name. The name of the variable
starts with an indication about its scope. The scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and response)
"req" : the variable is shared only during request processing
"res" : the variable is shared only during response processing
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
Returns value of <fieldname> found in input MQTT payload of type
<packettype>.
<packettype> can be either a string (case insensitive matching) or a numeric
value corresponding to the type of packet we're supposed to extract data
from.
Supported string and integers can be found here:
https://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718021
https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901022
<fieldname> depends on <packettype> and can be any of the following below.
(note that <fieldname> matching is case insensitive).
<property id> can only be found in MQTT v5.0 streams. check this table:
https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901029
- CONNECT (or 1): flags, protocol_name, protocol_version, client_identifier,
will_topic, will_payload, username, password, keepalive
OR any property ID as a numeric value (for MQTT v5.0
packets only):
17: Session Expiry Interval
33: Receive Maximum
39: Maximum Packet Size
34: Topic Alias Maximum
25: Request Response Information
23: Request Problem Information
21: Authentication Method
22: Authentication Data
18: Will Delay Interval
1: Payload Format Indicator
2: Message Expiry Interval
3: Content Type
8: Response Topic
9: Correlation Data
Not supported yet:
38: User Property
- CONNACK (or 2): flags, protocol_version, reason_code
OR any property ID as a numeric value (for MQTT v5.0
packets only):
17: Session Expiry Interval
33: Receive Maximum
36: Maximum QoS
37: Retain Available
39: Maximum Packet Size
18: Assigned Client Identifier
34: Topic Alias Maximum
31: Reason String
40; Wildcard Subscription Available
41: Subscription Identifiers Available
42: Shared Subscription Available
19: Server Keep Alive
26: Response Information
28: Server Reference
21: Authentication Method
22: Authentication Data
Not supported yet:
38: User Property
Due to current HAProxy design, only the first message sent by the client and
the server can be parsed. Thus this converter can extract data only from
CONNECT and CONNACK packet types. CONNECT is the first message sent by the
client and CONNACK is the first response sent by the server.
Example:
acl data_in_buffer req.len ge 4
tcp-request content set-var(txn.username) \
req.payload(0,0),mqtt_field_value(connect,protocol_name) \
if data_in_buffer
tcp-request content set-var(txn.username) \
req.payload(0,0),mqtt_field_value(1,protocol_name) \
if data_in_buffer
Checks that the binary input is a valid MQTT packet. It returns a boolean.
Due to current HAProxy design, only the first message sent by the client and
the server can be parsed. Thus this converter can extract data only from
CONNECT and CONNACK packet types. CONNECT is the first message sent by the
client and CONNACK is the first response sent by the server.
Only MQTT 3.1, 3.1.1 and 5.0 are supported.
Example:
acl data_in_buffer req.len ge 4
tcp-request content reject unless { req.payload(0,0),mqtt_is_valid }
This works like "
ltime" but takes an input in milliseconds. It also supports
the %N conversion specifier inspired by date(1).
Converts an integer supposed to contain a date since epoch to a string
representing this date in local time using a format defined by the <format>
string using strftime(3). The purpose is to allow any date format to be used
in logs. An optional <offset> in milliseconds may be applied to the input date
(positive or negative). See the strftime() man page for the format supported
by your operating system.
The %N conversion specifier allows you to output the nanoseconds part of the
date, precision is limited since the input is milliseconds.
(000000000..999000000). %N can take a width argument between % and N. It is
useful to display milliseconds (%3N) or microseconds (%6N). The default and
maximum width is 9 (%N = %9N).
See also the utime converter for UTC as well as "
ltime" and "
us_ltime"
converters.
Example :
log-format %[accept_date(ms),ms_ltime("%Y/%m/%d/%H:%M:%S.%3N %z")]\ %ci:%cp
This works like "
utime" but takes an input in milliseconds. It also supports
the %N conversion specifier inspired by date(1).
Converts an integer supposed to contain a date since epoch to a string
representing this date in UTC time using a format defined by the <format>
string using strftime(3). The purpose is to allow any date format to be used
in logs. An optional <offset> in milliseconds may be applied to the input date
(positive or negative). See the strftime() man page for the format supported
by your operating system.
The %N conversion specifier allows you to output the nanoseconds part of the
date, precision is limited since the input is milliseconds.
(000000000..999000000). %N can take a width argument between % and N. It is
useful to display milliseconds (%3N) or microseconds (%6N). The default and
maximum width is 9 (%N = %9N).
See also the ltime converter for local as well as "
utime" and "
us_utime"
converters.
Example :
log-format %[accept_date(ms),ms_utime("%Y/%m/%d/%H:%M:%S.%3N %z")]\ %ci:%cp
Multiplies the input value of type signed integer by <value>, and returns
the product as an signed integer. In case of overflow, the largest possible
value for the sign is returned so that the operation doesn't wrap around.
<value> can be a numeric value or a variable name. The name of the variable
starts with an indication about its scope. The scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and response)
"req" : the variable is shared only during request processing
"res" : the variable is shared only during response processing
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
Takes an input value of type string, interprets it as a backend name and
returns the number of usable servers in that backend. Can be used in places
where we want to look up a backend from a dynamic name, like a result of a
map lookup.
Takes the input value of type signed integer, computes the opposite value,
and returns the remainder as an signed integer. 0 is identity. This operator
is provided for reversed subtracts : in order to subtract the input from a
constant, simply perform a "neg,add(value)".
Returns a boolean FALSE if the input value of type signed integer is
non-null, otherwise returns TRUE. Used in conjunction with and(), it can be
used to report true/false for bit testing on input values (e.g. verify the
absence of a flag).
Returns a boolean TRUE if the input value of type signed integer is odd
otherwise returns FALSE. It is functionally equivalent to "and(1),bool".
Performs a bitwise "OR" between <value> and the input value of type signed
integer, and returns the result as an signed integer. <value> can be a
numeric value or a variable name. The name of the variable starts with an
indication about its scope. The scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and response)
"req" : the variable is shared only during request processing
"res" : the variable is shared only during response processing
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
This extracts the first occurrence of the parameter <name> in the input string
where parameters are delimited by <delim>, which defaults to "&", and the name
and value of the parameter are separated by a "=". If there is no "=" and
value before the end of the parameter segment, it is treated as equivalent to
a value of an empty string.
This can be useful for extracting parameters from a query string, or possibly
a x-www-form-urlencoded body. In particular, `query,param(<name>)` can be used
as an alternative to `urlp(<name>)` which only uses "&" as a delimiter,
whereas "
urlp" also uses "?" and ";".
Note that this converter doesn't do anything special with url encoded
characters. If you want to decode the value, you can use the url_dec converter
on the output. If the name of the parameter in the input might contain encoded
characters, you'll probably want do normalize the input before calling
"
param". This can be done using "http-request normalize-uri", in particular
the percent-decode-unreserved and percent-to-uppercase options.
Example :
str(a=b&c=d&a=r),param(a)
str(a&b=c),param(a)
str(a=&b&c=a),param(b)
str(a=1;b=2;c=4),param(b,;)
query,param(redirect_uri),urldec()
Converts a string which contains a Host header value into an integer by
returning its port.
The input must respect the format of the host header value
(rfc9110#section-7.2). It will support that kind of input: hostname,
hostname:80, 127.0.0.1, 127.0.0.1:80, [::1], [::1]:80.
If no port were provided in the input, it will return 0.
This extracts the protocol buffers message field in raw mode of an input binary
sample representation of a protocol buffer message with <field_number> as field
number (dotted notation) if <field_type> is not present, or as an integer sample
if this field is present (see also "
ungrpc" below).
The list of the authorized types is the following one: "int32", "int64", "uint32",
"uint64", "sint32", "sint64", "
bool", "enum" for the "varint" wire type 0
"fixed64", "sfixed64", "double" for the 64bit wire type 1, "fixed32", "sfixed32",
"float" for the wire type 5. Note that "string" is considered as a length-delimited
type, so it does not require any <field_type> argument to be extracted.
More information may be found here about the protocol buffers message field types:
https://developers.google.com/protocol-buffers/docs/encoding
regsub(
<regex>,
<subst>[,<flags>])
Applies a regex-based substitution to the input string. It does the same
operation as the well-known "sed" utility with "s/<regex>/<subst>/". By
default it will replace in the input string the first occurrence of the
largest part matching the regular expression <regex> with the substitution
string <subst>. It is possible to replace all occurrences instead by adding
the flag "g" in the third argument <flags>. It is also possible to make the
regex case insensitive by adding the flag "i" in <flags>. Since <flags> is a
string, it is made up from the concatenation of all desired flags. Thus if
both "i" and "g" are desired, using "gi" or "ig" will have the same effect.
The first use of this converter is to replace certain characters or sequence
of characters with other ones.
It is highly recommended to enclose the regex part using protected quotes to
improve clarity and never have a closing parenthesis from the regex mixed up
with the parenthesis from the function. Just like in Bourne shell, the first
level of quotes is processed when delimiting word groups on the line, a
second level is usable for argument. It is recommended to use single quotes
outside since these ones do not try to resolve backslashes nor dollar signs.
Examples:
http-request set-header x-path "%[hdr(x-path),regsub('/+','/','g')]"
http-request set-header x-query "%[query,regsub([?;&]*,'')]"
http-request redirect location %[url,'regsub("(foo|bar)([0-9]+)?","\2\1",i)']
http-request redirect location %[url,regsub(\"(foo|bar)([0-9]+)?\",\"\2\1\",i)]
Extracts a single field/parameter from RFC 7239 compliant header value input.
Supported fields are:
- proto: either 'http' or 'https'
- host: http compliant host
- for: RFC7239 node
- by: RFC7239 node
More info here:
https://www.rfc-editor.org/rfc/rfc7239.html#section-6
Example:
http-request set-var(req.fhost) req.hdr(forwarded),rfc7239_field(host)
http-request set-var(req.ffor) req.hdr(forwarded),rfc7239_field(for)
Returns true if input header is RFC 7239 compliant header value and false
otherwise.
Example:
acl valid req.hdr(forwarded),rfc7239_is_valid
Converts RFC7239 node (provided by 'for' or 'by' 7239 header fields)
into its corresponding nodename final form:
- ipv4 address
- ipv6 address
- 'unknown'
- '_obfs' identifier
Example:
http-request set-var(req.fnn) req.hdr(forwarded),rfc7239_field(for),rfc7239_n2nn
Converts RFC7239 node (provided by 'for' or 'by' 7239 header fields)
into its corresponding nodeport final form:
- unsigned integer
- '_obfs' identifier
Example:
http-request set-var(req.fnp) req.hdr(forwarded),rfc7239_field(by),rfc7239_n2np
Skips any characters from <chars> from the end of the string representation
of the input sample.
Hashes a binary input sample into an unsigned 32-bit quantity using the SDBM
hash function. Optionally, it is possible to apply a full avalanche hash
function to the output if the optional <avalanche> argument equals 1. This
converter uses the same functions as used by the various hash-based load
balancing algorithms, so it will provide exactly the same results. It is
mostly intended for debugging, but can be used as a stick-table entry to
collect rough statistics. It must not be used for security purposes as a
32-bit hash is trivial to break. See also "
crc32", "
djb2", "
wt6", "
crc32c",
and the "
hash-type" directive.
Compares the contents of <var> with the input value. Both values are treated
as a binary string. Returns a boolean indicating whether both binary strings
match.
If both binary strings have the same length then the comparison will be
performed in constant time.
Please note that this converter is only available when HAProxy has been
compiled with USE_OPENSSL.
Example :
http-request set-var(txn.token) hdr(token)
acl token_given str(my_secret_token),secure_memcmp(txn.token)
Sets a variable with the input content and returns the content on the output
as-is if all of the specified conditions are true (see below for a list of
possible conditions). The variable keeps the value and the associated input
type. The name of the variable starts with an indication about its scope. The
scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and
response),
"req" : the variable is shared only during request processing,
"res" : the variable is shared only during response processing.
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
You can pass at most four conditions to the converter among the following
possible conditions :
- "ifexists"/"ifnotexists":
Checks if the variable already existed before the current set-var call.
A variable is usually created through a successful set-var call.
Note that variables of scope "
proc" are created during configuration
parsing so the "ifexists" condition will always be true for them.
- "ifempty"/"ifnotempty":
Checks if the input is empty or not.
Scalar types are never empty so the ifempty condition will be false for
them regardless of the input's contents (integers, booleans, IPs ...).
- "ifset"/"ifnotset":
Checks if the variable was previously set or not, or if unset-var was
called on the variable.
A variable that does not exist yet is considered as not set. A "
proc"
variable can exist while not being set since they are created during
configuration parsing.
- "ifgt"/"iflt":
Checks if the content of the variable is "greater than" or "less than"
the input. This check can only be performed if both the input and
the variable are of type integer. Otherwise, the check is considered as
true by default.
Converts a binary input sample to a SHA-1 digest. The result is a binary
sample with length of 20 bytes.
Converts a binary input sample to a digest in the SHA-2 family. The result
is a binary sample with length of <bits>/8 bytes.
Valid values for <bits> are 224, 256, 384, 512, each corresponding to
SHA-<bits>. The default value is 256.
Please note that this converter is only available when HAProxy has been
compiled with USE_OPENSSL.
Takes an input value of type string, either a server name or <backend>/<server>
format and returns the number of queued streams on that server. Can be used
in places where we want to look up queued streams from a dynamic name, like a
cookie value (e.g. req.cook(SRVID),srv_queue) and then make a decision to break
persistence or direct a request elsewhere.
Compares the contents of <var> with the input value of type string. Returns
the result as a signed integer compatible with strcmp(3): 0 if both strings
are identical. A value less than 0 if the left string is lexicographically
smaller than the right string or if the left string is shorter. A value greater
than 0 otherwise (right string greater than left string or the right string is
shorter).
See also the secure_memcmp converter if you need to compare two binary
strings in constant time.
Example :
http-request set-var(txn.host) hdr(host)
acl ssl_sni_http_host_match ssl_fc_sni,strcmp(txn.host) eq 0
Subtracts <value> from the input value of type signed integer, and returns
the result as an signed integer. Note: in order to subtract the input from
a constant, simply perform a "neg,add(value)". <value> can be a numeric value
or a variable name. The name of the variable starts with an indication about
its scope. The scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and
response),
"req" : the variable is shared only during request processing,
"res" : the variable is shared only during response processing.
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the average client-to-server
bytes rate associated with the input sample in the designated table, measured
in amount of bytes over the period configured in the table. See also the
sc_bytes_in_rate sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the average server-to-client
bytes rate associated with the input sample in the designated table, measured
in amount of bytes over the period configured in the table. See also the
sc_bytes_out_rate sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the cumulative number of incoming
connections associated with the input sample in the designated table. See
also the sc_conn_cnt sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the current amount of concurrent
tracked connections associated with the input sample in the designated table.
See also the sc_conn_cur sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the average incoming connection
rate associated with the input sample in the designated table. See also the
sc_conn_rate sample fetch keyword.
Uses the input sample to perform a look up in the specified table. If the key
is not found in the table, the converter fails except if <default_value> is
set: this makes the converter succeed and return <default_value>. If the key
is found the converter returns the key expiration delay associated with the
input sample in the designated table.
See also the table_idle sample fetch keyword.
Uses the string representation of the input sample to perform a lookup in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the current value of the
General Purpose Counter at the index <idx> of the array associated
to the input sample in the designated <table>. <idx> is an integer
between 0 and 99.
If there is no GPC stored at this index, it also returns the boolean value 0.
This applies only to the 'gpc' array data_type (and not to the legacy
'gpc0' nor 'gpc1' data_types).
See also the sc_get_gpc sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the current value of the first
general purpose counter associated with the input sample in the designated
table. See also the sc_get_gpc0 sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the frequency which the gpc0
counter was incremented over the configured period in the table, associated
with the input sample in the designated table. See also the sc_get_gpc0_rate
sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the current value of the second
general purpose counter associated with the input sample in the designated
table. See also the sc_get_gpc1 sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the frequency which the gpc1
counter was incremented over the configured period in the table, associated
with the input sample in the designated table. See also the sc_get_gpc1_rate
sample fetch keyword.
Uses the string representation of the input sample to perform a lookup in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the frequency which the Global
Purpose Counter at index <idx> of the array (associated to the input sample
in the designated stick-table <table>) was incremented over the
configured period. <idx> is an integer between 0 and 99.
If there is no gpc_rate stored at this index, it also returns the boolean
value 0.
This applies only to the 'gpc_rate' array data_type (and not to the
legacy 'gpc0_rate' nor 'gpc1_rate' data_types).
See also the sc_gpc_rate sample fetch keyword.
Uses the string representation of the input sample to perform a lookup in
the specified table. If the key is not found in the table, boolean value zero
is returned. Otherwise the converter returns the current value of the general
purpose tag at the index <idx> of the array associated to the input sample
in the designated <table>. <idx> is an integer between 0 and 99.
If there is no GPT stored at this index, it also returns the boolean value 0.
This applies only to the 'gpt' array data_type (and not on the legacy 'gpt0'
data-type).
See also the sc_get_gpt sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, boolean value zero
is returned. Otherwise the converter returns the current value of the first
general purpose tag associated with the input sample in the designated table.
See also the sc_get_gpt0 sample fetch keyword.
HAPEE: this function is provided by the "extensions" module
Uses the string representation of the input sample to perform a lookup in the
specified table. If the key is not found in the table, the optional <default>
string is returned, otherwise an empty string. If the key is found, the
converter reads up to <gptcnt> GPT entries starting at index <gptidx> of the
array associated to the input sample in the designated <table>, converts them
to a string and returns that string. <gptidx> is an integer between 0 and 99.
If there is no GPT stored at this index, the default or empty string is
returned. The special value "0" for <gptcnt> will read all GPT entries till
the end. See also the sc-set-gptstr action and the sc_get_gptstr sample fetch
keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the cumulative number of HTTP
errors associated with the input sample in the designated table. See also the
sc_http_err_cnt sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the average rate of HTTP errors associated with the
input sample in the designated table, measured in amount of errors over the
period configured in the table. See also the sc_http_err_rate sample fetch
keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the cumulative number of HTTP
failures associated with the input sample in the designated table. See also
the sc_http_fail_cnt sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the average rate of HTTP failures associated with the
input sample in the designated table, measured in amount of failures over the
period configured in the table. See also the sc_http_fail_rate sample fetch
keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the cumulative number of HTTP
requests associated with the input sample in the designated table. See also
the sc_http_req_cnt sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the average rate of HTTP requests associated with the
input sample in the designated table, measured in amount of requests over the
period configured in the table. See also the sc_http_req_rate sample fetch
keyword.
Uses the input sample to perform a look up in the specified table. If the key
is not found in the table, the converter fails except if <default_value> is
set: this makes the converter succeed and return <default_value>. If the key
is found the converter returns the time the key entry associated with the
input sample in the designated table remained idle since the last time it was
updated.
See also the table_expire sample fetch keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the cumulative number of client-
to-server data associated with the input sample in the designated table,
measured in kilobytes. The test is currently performed on 32-bit integers,
which limits values to 4 terabytes. See also the sc_kbytes_in sample fetch
keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the cumulative number of server-
to-client data associated with the input sample in the designated table,
measured in kilobytes. The test is currently performed on 32-bit integers,
which limits values to 4 terabytes. See also the sc_kbytes_out sample fetch
keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the server ID associated with
the input sample in the designated table. A server ID is associated to a
sample by a "
stick" rule when a connection to a server succeeds. A server ID
zero means that no server is associated with this key.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the cumulative number of incoming
sessions associated with the input sample in the designated table. Note that
a session here refers to an incoming connection being accepted by the
"
tcp-request connection" rulesets. See also the sc_sess_cnt sample fetch
keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the average incoming session
rate associated with the input sample in the designated table. Note that a
session here refers to an incoming connection being accepted by the
"
tcp-request connection" rulesets. See also the sc_sess_rate sample fetch
keyword.
Uses the string representation of the input sample to perform a look up in
the specified table. If the key is not found in the table, integer value zero
is returned. Otherwise the converter returns the current amount of concurrent
connections tracking the same key as the input sample in the designated
table. It differs from table_conn_cur in that it does not rely on any stored
information but on the table's reference count (the "use" value which is
returned by "show table" on the CLI). This may sometimes be more suited for
layer7 tracking. It can be used to tell a server how many concurrent
connections there are from a given address for example. See also the
sc_trackers sample fetch keyword.
This converter is the base64url variant of b64dec converter. base64url
encoding is the "URL and Filename Safe Alphabet" variant of base64 encoding.
It is also the encoding used in JWT (JSON Web Token) standard.
Example:
http-request set-var(txn.token_payload) req.hdr(Authorization),word(2,.),ub64dec
This converter is the base64url variant of base64 converter.
ungrpc(
<field_number>,
[<field_type>])
This extracts the protocol buffers message field in raw mode of an input binary
sample representation of a gRPC message with <field_number> as field number
(dotted notation) if <field_type> is not present, or as an integer sample if this
field is present.
The list of the authorized types is the following one: "int32", "int64", "uint32",
"uint64", "sint32", "sint64", "
bool", "enum" for the "varint" wire type 0
"fixed64", "sfixed64", "double" for the 64bit wire type 1, "fixed32", "sfixed32",
"float" for the wire type 5. Note that "string" is considered as a length-delimited
type, so it does not require any <field_type> argument to be extracted.
More information may be found here about the protocol buffers message field types:
https://developers.google.com/protocol-buffers/docs/encoding
Example:
// with such a protocol buffer .proto file content adapted from
// https://github.com/grpc/grpc/blob/master/examples/protos/route_guide.proto
message Point {
int32 latitude = 1;
int32 longitude = 2;
}
message PPoint {
Point point = 59;
}
message Rectangle {
// One corner of the rectangle.
PPoint lo = 48;
// The other corner of the rectangle.
PPoint hi = 49;
}
let's say a body request is made of a "Rectangle" object value (two PPoint
protocol buffers messages), the four protocol buffers fields could be
extracted with these "
ungrpc" directives:
req.body,ungrpc(48.59.1,int32) # "latitude" of "lo" first PPoint
req.body,ungrpc(48.59.2,int32) # "longitude" of "lo" first PPoint
req.body,ungrpc(49.59.1,int32) # "latitude" of "hi" second PPoint
req.body,ungrpc(49.59.2,int32) # "longitude" of "hi" second PPoint
We could also extract the intermediary 48.59 field as a binary sample as follows:
req.body,ungrpc(48.59)
As a gRPC message is always made of a gRPC header followed by protocol buffers
messages, in the previous example the "latitude" of "lo" first PPoint
could be extracted with these equivalent directives:
req.body,ungrpc(48.59),protobuf(1,int32)
req.body,ungrpc(48),protobuf(59.1,int32)
req.body,ungrpc(48),protobuf(59),protobuf(1,int32)
Note that the first convert must be "
ungrpc", the remaining ones must be
"
protobuf" and only the last one may have or not a second argument to
interpret the previous binary sample.
Unsets a variable if the input content is defined. The name of the variable
starts with an indication about its scope. The scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and
response),
"req" : the variable is shared only during request processing,
"res" : the variable is shared only during response processing.
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
Convert a string sample to upper case. This can only be placed after a string
sample fetch function or after a transformation keyword returning a string
type. The result is of type string.
Takes an url-encoded string provided as input and returns the decoded version
as output. The input and the output are of type string. If the <in_form>
argument is set to a non-zero integer value, the input string is assumed to
be part of a form or query string and the '+' character will be turned into a
space (' '). Otherwise this will only happen after a question mark indicating
a query string ('?').
Takes a string provided as input and returns the encoded version as output.
The input and the output are of type string. By default the type of encoding
is meant for `query` type. There is no other type supported for now but the
optional argument is here for future changes.
This works like "
ltime" but takes an input in microseconds. It also supports
the %N conversion specifier inspired by date(1).
Converts an integer supposed to contain a date since epoch to a string
representing this date in local time using a format defined by the <format>
string using strftime(3). The purpose is to allow any date format to be used
in logs. An optional <offset> in microseconds may be applied to the input
date (positive or negative). See the strftime() man page for the format
supported by your operating system.
The %N conversion specifier allows you to output the nanoseconds part of the
date, precision is limited since the input is microseconds.
(000000000..999999000). %N can take a width argument between % and N. It is
useful to display milliseconds (%3N) or microseconds (%6N). The default and
maximum width is 9 (%N = %9N).
See also the "
utime" converter for UTC as well as "
ltime" and "
ms_ltime"
converters.
Example :
log-format %[accept_date(us),us_ltime("%Y/%m/%d/%H:%M:%S.%6N %z")]\ %ci:%cp
This works like "
utime" but takes an input in microseconds. It also supports
the %N conversion specifier inspired by date(1).
Converts an integer supposed to contain a date since epoch to a string
representing this date in UTC time using a format defined by the <format>
string using strftime(3). The purpose is to allow any date format to be used
in logs. An optional <offset> in microseconds may be applied to the input
date (positive or negative). See the strftime() man page for the format
supported by your operating system.
The %N conversion specifier allows you to output the nanoseconds part of the
date, precision is limited since the input is microseconds.
(000000000..999999000). %N can take a width argument between % and N. It is
useful to display milliseconds (%3N) or microseconds (%6N). The default and
maximum width is 9 (%N = %9N).
See also the "
ltime" converter for local as well as "
utime" and "
ms_utime"
converters.
Example :
log-format %[accept_date(us),us_utime("%Y/%m/%d/%H:%M:%S.%6N %z")]\ %ci:%cp
utime(
<format>[,<offset>])
Converts an integer supposed to contain a date since epoch to a string
representing this date in UTC time using a format defined by the <format>
string using strftime(3). The purpose is to allow any date format to be used
in logs. An optional <offset> in seconds may be applied to the input date
(positive or negative). See the strftime() man page for the format supported
by your operating system. See also the "
ltime" converter as well as "
ms_utime"
and "
us_utime".
Example :
log-format %[date,utime(%Y%m%d%H%M%S)]\ %ci:%cp
word(
<index>,
<delimiters>[,<count>])
Extracts the nth word counting from the beginning (positive index) or from
the end (negative index) considering given delimiters from an input string.
Indexes start at 1 or -1 and delimiters are a string formatted list of chars.
Empty words are skipped. This means that delimiters at the start or end of
the input string are ignored and consecutive delimiters within the input
string are considered to be a single delimiter.
Optionally you can specify <count> of words to extract (default: 1).
Value of 0 indicates extraction of all remaining words.
Example :
str(f1_f2_f3__f5),word(4,_)
str(f1_f2_f3__f5),word(5,_)
str(f1_f2_f3__f5),word(2,_,0)
str(f1_f2_f3__f5),word(3,_,2)
str(f1_f2_f3__f5),word(-2,_,3)
str(f1_f2_f3__f5),word(-3,_,0)
str(/f1/f2/f3/f4),word(1,/)
str(/f1////f2/f3/f4),word(1,/)
Hashes a binary input sample into an unsigned 32-bit quantity using the WT6
hash function. Optionally, it is possible to apply a full avalanche hash
function to the output if the optional <avalanche> argument equals 1. This
converter uses the same functions as used by the various hash-based load
balancing algorithms, so it will provide exactly the same results. It is
mostly intended for debugging, but can be used as a stick-table entry to
collect rough statistics. It must not be used for security purposes as a
32-bit hash is trivial to break. See also "
crc32", "
djb2", "
sdbm", "
crc32c",
and the "
hash-type" directive.
Convert a numerical value to its corresponding X509_V_ERR constant name. It
is useful in ACL in order to have a configuration which works with multiple
version of OpenSSL since some codes might change when changing version.
When the corresponding constant name was not found, outputs the numerical
value as a string.
The list of constant provided by OpenSSL can be found at
https://www.openssl.org/docs/manmaster/man3/X509_STORE_CTX_get_error.html#ERROR-CODES
Be careful to read the page for the right version of OpenSSL.
Example:
bind :443 ssl crt common.pem ca-file ca-auth.crt verify optional crt-ignore-err X509_V_ERR_CERT_REVOKED,X509_V_ERR_CERT_HAS_EXPIRED
acl cert_expired ssl_c_verify,x509_v_err_str -m str X509_V_ERR_CERT_HAS_EXPIRED
acl cert_revoked ssl_c_verify,x509_v_err_str -m str X509_V_ERR_CERT_REVOKED
acl cert_ok ssl_c_verify,x509_v_err_str -m str X509_V_OK
http-response add-header X-SSL Ok if cert_ok
http-response add-header X-SSL Expired if cert_expired
http-response add-header X-SSL Revoked if cert_revoked
http-response add-header X-SSL-verify %[ssl_c_verify,x509_v_err_str]
Performs a bitwise "XOR" (exclusive OR) between <value> and the input value
of type signed integer, and returns the result as an signed integer.
<value> can be a numeric value or a variable name. The name of the variable
starts with an indication about its scope. The scopes allowed are:
"
proc" : the variable is shared with the whole process
"sess" : the variable is shared with the whole session
"txn" : the variable is shared with the transaction (request and
response),
"req" : the variable is shared only during request processing,
"res" : the variable is shared only during response processing.
This prefix is followed by a name. The separator is a '.'. The name may only
contain characters 'a-z', 'A-Z', '0-9', '.' and '_'.
Hashes a binary input sample into a signed 64-bit quantity using the XXH3
64-bit variant of the XXhash hash function. This hash supports a seed which
defaults to zero but a different value maybe passed as the <seed> argument.
This hash is known to be very good and very fast so it can be used to hash
URLs and/or URL parameters for use as stick-table keys to collect statistics
with a low collision rate, though care must be taken as the algorithm is not
considered as cryptographically secure.
Hashes a binary input sample into an unsigned 32-bit quantity using the 32-bit
variant of the XXHash hash function. This hash supports a seed which defaults
to zero but a different value maybe passed as the <seed> argument. This hash
is known to be very good and very fast so it can be used to hash URLs and/or
URL parameters for use as stick-table keys to collect statistics with a low
collision rate, though care must be taken as the algorithm is not considered
as cryptographically secure.
Hashes a binary input sample into a signed 64-bit quantity using the 64-bit
variant of the XXHash hash function. This hash supports a seed which defaults
to zero but a different value maybe passed as the <seed> argument. This hash
is known to be very good and very fast so it can be used to hash URLs and/or
URL parameters for use as stick-table keys to collect statistics with a low
collision rate, though care must be taken as the algorithm is not considered
as cryptographically secure.