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----------------------
HAProxy
Configuration Manual
----------------------
version 1.4
willy tarreau
2009/06/09
This document covers the configuration language as implemented in the version
specified above. It does not provide any hint, example or advice. For such
documentation, please refer to the Reference Manual or the Architecture Manual.
The summary below is meant to help you search sections by name and navigate
through the document.
Note to documentation contributors :
This document is formated with 80 columns per line, with even number of
spaces for indentation and without tabs. Please follow these rules strictly
so that it remains easily printable everywhere. If a line needs to be
printed verbatim and does not fit, please end each line with a backslash
('\') and continue on next line. If you add sections, please update the
summary below for easier searching.
Summary
-------
1. Quick reminder about HTTP
1.1. The HTTP transaction model
1.2. HTTP request
1.2.1. The Request line
1.2.2. The request headers
1.3. HTTP response
1.3.1. The Response line
1.3.2. The response headers
2. Configuring HAProxy
2.1. Configuration file format
2.2. Time format
3. Global parameters
3.1. Process management and security
3.2. Performance tuning
3.3. Debugging
4. Proxies
4.1. Proxy keywords matrix
4.2. Alphabetically sorted keywords reference
5. Server options
6. HTTP header manipulation
7. Using ACLs
7.1. Matching integers
7.2. Matching strings
7.3. Matching regular expressions (regexes)
7.4. Matching IPv4 addresses
7.5. Available matching criteria
7.5.1. Matching at Layer 4 and below
7.5.2. Matching contents at Layer 4
7.5.3. Matching at Layer 7
7.6. Pre-defined ACLs
7.7. Using ACLs to form conditions
8. Logging
8.1. Log levels
8.2. Log formats
8.2.1. Default log format
8.2.2. TCP log format
8.2.3. HTTP log format
8.3. Advanced logging options
8.3.1. Disabling logging of external tests
8.3.2. Logging before waiting for the session to terminate
8.3.3. Raising log level upon errors
8.3.4. Disabling logging of successful connections
8.4. Timing events
8.5. Session state at disconnection
8.6. Non-printable characters
8.7. Capturing HTTP cookies
8.8. Capturing HTTP headers
8.9. Examples of logs
9. Statistics and monitoring
9.1. CSV format
9.2. Unix Socket commands
1. Quick reminder about HTTP
----------------------------
When haproxy is running in HTTP mode, both the request and the response are
fully analyzed and indexed, thus it becomes possible to build matching criteria
on almost anything found in the contents.
However, it is important to understand how HTTP requests and responses are
formed, and how HAProxy decomposes them. It will then become easier to write
correct rules and to debug existing configurations.
1.1. The HTTP transaction model
-------------------------------
The HTTP protocol is transaction-driven. This means that each request will lead
to one and only one response. Traditionnally, a TCP connection is established
from the client to the server, a request is sent by the client on the
connection, the server responds and the connection is closed. A new request
will involve a new connection :
[CON1] [REQ1] ... [RESP1] [CLO1] [CON2] [REQ2] ... [RESP2] [CLO2] ...
In this mode, called the "HTTP close" mode, there are as many connection
establishments as there are HTTP transactions. Since the connection is closed
by the server after the response, the client does not need to know the content
length.
Due to the transactional nature of the protocol, it was possible to improve it
to avoid closing a connection between two subsequent transactions. In this mode
however, it is mandatory that the server indicates the content length for each
response so that the client does not wait indefinitely. For this, a special
header is used: "Content-length". This mode is called the "keep-alive" mode :
[CON] [REQ1] ... [RESP1] [REQ2] ... [RESP2] [CLO] ...
Its advantages are a reduced latency between transactions, and less processing
power required on the server side. It is generally better than the close mode,
but not always because the clients often limit their concurrent connections to
a smaller value. HAProxy currently does not support the HTTP keep-alive mode,
but knows how to transform it to the close mode.
A last improvement in the communications is the pipelining mode. It still uses
keep-alive, but the client does not wait for the first response to send the
second request. This is useful for fetching large number of images composing a
page :
[CON] [REQ1] [REQ2] ... [RESP1] [RESP2] [CLO] ...
This can obviously have a tremendous benefit on performance because the network
latency is eliminated between subsequent requests. Many HTTP agents do not
correctly support pipelining since there is no way to associate a response with
the corresponding request in HTTP. For this reason, it is mandatory for the
server to reply in the exact same order as the requests were received.
Right now, HAProxy only supports the first mode (HTTP close) if it needs to
process the request. This means that for each request, there will be one TCP
connection. If keep-alive or pipelining are required, HAProxy will still
support them, but will only see the first request and the first response of
each transaction. While this is generally problematic with regards to logs,
content switching or filtering, it most often causes no problem for persistence
with cookie insertion.
1.2. HTTP request
-----------------
First, let's consider this HTTP request :
Line Contents
number
1 GET /serv/login.php?lang=en&profile=2 HTTP/1.1
2 Host: www.mydomain.com
3 User-agent: my small browser
4 Accept: image/jpeg, image/gif
5 Accept: image/png
1.2.1. The Request line
-----------------------
Line 1 is the "request line". It is always composed of 3 fields :
- a METHOD : GET
- a URI : /serv/login.php?lang=en&profile=2
- a version tag : HTTP/1.1
All of them are delimited by what the standard calls LWS (linear white spaces),
which are commonly spaces, but can also be tabs or line feeds/carriage returns
followed by spaces/tabs. The method itself cannot contain any colon (':') and
is limited to alphabetic letters. All those various combinations make it
desirable that HAProxy performs the splitting itself rather than leaving it to
the user to write a complex or inaccurate regular expression.
The URI itself can have several forms :
- A "relative URI" :
/serv/login.php?lang=en&profile=2
It is a complete URL without the host part. This is generally what is
received by servers, reverse proxies and transparent proxies.
- An "absolute URI", also called a "URL" :
http://192.168.0.12:8080/serv/login.php?lang=en&profile=2
It is composed of a "scheme" (the protocol name followed by '://'), a host
name or address, optionally a colon (':') followed by a port number, then
a relative URI beginning at the first slash ('/') after the address part.
This is generally what proxies receive, but a server supporting HTTP/1.1
must accept this form too.
- a star ('*') : this form is only accepted in association with the OPTIONS
method and is not relayable. It is used to inquiry a next hop's
capabilities.
- an address:port combination : 192.168.0.12:80
This is used with the CONNECT method, which is used to establish TCP
tunnels through HTTP proxies, generally for HTTPS, but sometimes for
other protocols too.
In a relative URI, two sub-parts are identified. The part before the question
mark is called the "path". It is typically the relative path to static objects
on the server. The part after the question mark is called the "query string".
It is mostly used with GET requests sent to dynamic scripts and is very
specific to the language, framework or application in use.
1.2.2. The request headers
--------------------------
The headers start at the second line. They are composed of a name at the
beginning of the line, immediately followed by a colon (':'). Traditionally,
an LWS is added after the colon but that's not required. Then come the values.
Multiple identical headers may be folded into one single line, delimiting the
values with commas, provided that their order is respected. This is commonly
encountered in the "Cookie:" field. A header may span over multiple lines if
the subsequent lines begin with an LWS. In the example in 1.2, lines 4 and 5
define a total of 3 values for the "Accept:" header.
Contrary to a common mis-conception, header names are not case-sensitive, and
their values are not either if they refer to other header names (such as the
"Connection:" header).
The end of the headers is indicated by the first empty line. People often say
that it's a double line feed, which is not exact, even if a double line feed
is one valid form of empty line.
Fortunately, HAProxy takes care of all these complex combinations when indexing
headers, checking values and counting them, so there is no reason to worry
about the way they could be written, but it is important not to accuse an
application of being buggy if it does unusual, valid things.
Important note:
As suggested by RFC2616, HAProxy normalizes headers by replacing line breaks
in the middle of headers by LWS in order to join multi-line headers. This
is necessary for proper analysis and helps less capable HTTP parsers to work
correctly and not to be fooled by such complex constructs.
1.3. HTTP response
------------------
An HTTP response looks very much like an HTTP request. Both are called HTTP
messages. Let's consider this HTTP response :
Line Contents
number
1 HTTP/1.1 200 OK
2 Content-length: 350
3 Content-Type: text/html
1.3.1. The Response line
------------------------
Line 1 is the "response line". It is always composed of 3 fields :
- a version tag : HTTP/1.1
- a status code : 200
- a reason : OK
The status code is always 3-digit. The first digit indicates a general status :
- 2xx = OK, content is following (eg: 200, 206)
- 3xx = OK, no content following (eg: 302, 304)
- 4xx = error caused by the client (eg: 401, 403, 404)
- 5xx = error caused by the server (eg: 500, 502, 503)
Please refer to RFC2616 for the detailed meaning of all such codes. The
"reason" field is just a hint, but is not parsed by clients. Anything can be
found there, but it's a common practice to respect the well-established
messages. It can be composed of one or multiple words, such as "OK", "Found",
or "Authentication Required".
Haproxy may emit the following status codes by itself :
Code When / reason
200 access to stats page, and when replying to monitoring requests
301 when performing a redirection, depending on the configured code
302 when performing a redirection, depending on the configured code
303 when performing a redirection, depending on the configured code
400 for an invalid or too large request
401 when an authentication is required to perform the action (when
accessing the stats page)
403 when a request is forbidden by a "block" ACL or "reqdeny" filter
408 when the request timeout strikes before the request is complete
500 when haproxy encounters an unrecoverable internal error, such as a
memory allocation failure, which should never happen
502 when the server returns an empty, invalid or incomplete response, or
when an "rspdeny" filter blocks the response.
503 when no server was available to handle the request, or in response to
monitoring requests which match the "monitor fail" condition
504 when the response timeout strikes before the server responds
The error 4xx and 5xx codes above may be customized (see "errorloc" in section
4.2).
1.3.2. The response headers
---------------------------
Response headers work exactly like request headers, and as such, HAProxy uses
the same parsing function for both. Please refer to paragraph 1.2.2 for more
details.
2. Configuring HAProxy
----------------------
2.1. Configuration file format
------------------------------
HAProxy's configuration process involves 3 major sources of parameters :
- the arguments from the command-line, which always take precedence
- the "global" section, which sets process-wide parameters
- the proxies sections which can take form of "defaults", "listen",
"frontend" and "backend".
The configuration file syntax consists in lines beginning with a keyword
referenced in this manual, optionally followed by one or several parameters
delimited by spaces. If spaces have to be entered in strings, then they must be
preceeded by a backslash ('\') to be escaped. Backslashes also have to be
escaped by doubling them.
2.2. Time format
----------------
Some parameters involve values representating time, such as timeouts. These
values are generally expressed in milliseconds (unless explicitly stated
otherwise) but may be expressed in any other unit by suffixing the unit to the
numeric value. It is important to consider this because it will not be repeated
for every keyword. Supported units are :
- us : microseconds. 1 microsecond = 1/1000000 second
- ms : milliseconds. 1 millisecond = 1/1000 second. This is the default.
- s : seconds. 1s = 1000ms
- m : minutes. 1m = 60s = 60000ms
- h : hours. 1h = 60m = 3600s = 3600000ms
- d : days. 1d = 24h = 1440m = 86400s = 86400000ms
3. Global parameters
--------------------
Parameters in the "global" section are process-wide and often OS-specific. They
are generally set once for all and do not need being changed once correct. Some
of them have command-line equivalents.
The following keywords are supported in the "global" section :
* Process management and security
- chroot
- daemon
- gid
- group
- log
- nbproc
- pidfile
- uid
- ulimit-n
- user
- stats
* Performance tuning
- maxconn
- maxpipes
- noepoll
- nokqueue
- nopoll
- nosepoll
- nosplice
- spread-checks
- tune.maxaccept
- tune.maxpollevents
* Debugging
- debug
- quiet
3.1. Process management and security
------------------------------------
chroot <jail dir>
Changes current directory to <jail dir> and performs a chroot() there before
dropping privileges. This increases the security level in case an unknown
vulnerability would be exploited, since it would make it very hard for the
attacker to exploit the system. This only works when the process is started
with superuser privileges. It is important to ensure that <jail_dir> is both
empty and unwritable to anyone.
daemon
Makes the process fork into background. This is the recommended mode of
operation. It is equivalent to the command line "-D" argument. It can be
disabled by the command line "-db" argument.
gid <number>
Changes the process' group ID to <number>. It is recommended that the group
ID is dedicated to HAProxy or to a small set of similar daemons. HAProxy must
be started with a user belonging to this group, or with superuser privileges.
See also "group" and "uid".
group <group name>
Similar to "gid" but uses the GID of group name <group name> from /etc/group.
See also "gid" and "user".
log <address> <facility> [max level [min level]]
Adds a global syslog server. Up to two global servers can be defined. They
will receive logs for startups and exits, as well as all logs from proxies
configured with "log global".
<address> 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).
- 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
writeable).
<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
An optional level can be specified to filter outgoing messages. By default,
all messages are sent. If a maximum 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
nbproc <number>
Creates <number> processes when going daemon. This requires the "daemon"
mode. By default, only one process is created, which is the recommended mode
of operation. For systems limited to small sets of file descriptors per
process, it may be needed to fork multiple daemons. USING MULTIPLE PROCESSES
IS HARDER TO DEBUG AND IS REALLY DISCOURAGED. See also "daemon".
pidfile <pidfile>
Writes pids of all daemons into file <pidfile>. This option is equivalent to
the "-p" command line argument. The file must be accessible to the user
starting the process. See also "daemon".
stats socket <path> [{uid | user} <uid>] [{gid | group} <gid>] [mode <mode>]
Creates a UNIX socket in stream mode at location <path>. Any previously
existing socket will be backed up then replaced. Connections to this socket
will get a CSV-formated output of the process statistics in response to the
"show stat" command followed by a line feed, more general process information
in response to the "show info" command followed by a line feed, and a
complete list of all existing sessions in response to the "show sess" command
followed by a line feed.
On platforms which support it, it is possible to restrict access to this
socket by specifying numerical IDs after "uid" and "gid", or valid user and
group names after the "user" and "group" keywords. It is also possible to
restrict permissions on the socket by passing an octal value after the "mode"
keyword (same syntax as chmod). Depending on the platform, the permissions on
the socket will be inherited from the directory which hosts it, or from the
user the process is started with.
stats timeout <timeout, in milliseconds>
The default timeout on the stats socket is set to 10 seconds. It is possible
to change this value with "stats timeout". The value must be passed in
milliseconds, or be suffixed by a time unit among { us, ms, s, m, h, d }.
stats maxconn <connections>
By default, the stats socket is limited to 10 concurrent connections. It is
possible to change this value with "stats maxconn".
uid <number>
Changes the process' user ID to <number>. It is recommended that the user ID
is dedicated to HAProxy or to a small set of similar daemons. HAProxy must
be started with superuser privileges in order to be able to switch to another
one. See also "gid" and "user".
ulimit-n <number>
Sets the maximum number of per-process file-descriptors to <number>. By
default, it is automatically computed, so it is recommended not to use this
option.
user <user name>
Similar to "uid" but uses the UID of user name <user name> from /etc/passwd.
See also "uid" and "group".
3.2. Performance tuning
-----------------------
maxconn <number>
Sets the maximum per-process number of concurrent connections to <number>. It
is equivalent to the command-line argument "-n". Proxies will stop accepting
connections when this limit is reached. The "ulimit-n" parameter is
automatically adjusted according to this value. See also "ulimit-n".
maxpipes <number>
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.
noepoll
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 "nosepoll", and "nopoll".
nokqueue
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".
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 "nosepoll", and "nopoll" and
"nokqueue".
nosepoll
Disables the use of the "speculative epoll" event polling system on Linux. It
is equivalent to the command-line argument "-ds". The next polling system
used will generally be "epoll". See also "nosepoll", and "nopoll".
nosplice
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 verstions 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".
spread-checks <0..50, in percent>
Sometimes it is desirable to avoid sending 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.
tune.maxaccept <number>
Sets the maximum number of consecutive accepts that a process may perform on
a single wake up. High values give higher priority to high connection rates,
while lower values give higher priority to already established connections.
This value is limited to 100 by default in single process mode. However, in
multi-process mode (nbproc > 1), it defaults to 8 so that when one process
wakes up, it does not take all incoming connections for itself and leaves a
part of them to other processes. Setting this value to -1 completely disables
the limitation. It should normally not be needed to tweak this value.
tune.maxpollevents <number>
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.
3.3. Debugging
--------------
debug
Enables debug mode which dumps to stdout all exchanges, and disables forking
into background. It is the equivalent of the command-line argument "-d". It
should never be used in a production configuration since it may prevent full
system startup.
quiet
Do not display any message during startup. It is equivalent to the command-
line argument "-q".
4. Proxies
----------
Proxy configuration can be located in a set of sections :
- defaults <name>
- frontend <name>
- backend <name>
- listen <name>
A "defaults" section sets default parameters for all other sections following
its declaration. Those default parameters are reset by the next "defaults"
section. See below for the list of parameters which can be set in a "defaults"
section. The name is optional but its use is encouraged for better readability.
A "frontend" section describes a set of listening sockets accepting client
connections.
A "backend" section describes a set of servers to which the proxy will connect
to forward incoming connections.
A "listen" section defines a complete proxy with its frontend and backend
parts combined in one section. It is generally useful for TCP-only traffic.
All proxy names must be formed from upper and lower case letters, digits,
'-' (dash), '_' (underscore) , '.' (dot) and ':' (colon). ACL names are
case-sensitive, which means that "www" and "WWW" are two different proxies.
Historically, all proxy names could overlap, it just caused troubles in the
logs. Since the introduction of content switching, it is mandatory that two
proxies with overlapping capabilities (frontend/backend) have different names.
However, it is still permitted that a frontend and a backend share the same
name, as this configuration seems to be commonly encountered.
Right now, two major proxy modes are supported : "tcp", also known as layer 4,
and "http", also known as layer 7. In layer 4 mode, HAProxy simply forwards
bidirectionnal traffic between two sides. In layer 7 mode, HAProxy analyzes the
protocol, and can interact with it by allowing, blocking, switching, adding,
modifying, or removing arbitrary contents in requests or responses, based on
arbitrary criteria.
4.1. Proxy keywords matrix
--------------------------
The following list of keywords is supported. Most of them may only be used in a
limited set of section types. Some of them are marked as "deprecated" because
they are inherited from an old syntax which may be confusing or functionally
limited, and there are new recommended keywords to replace them. Keywords
listed with [no] can be optionally inverted using the "no" prefix, eg. "no
option contstats". This makes sense when the option has been enabled by default
and must be disabled for a specific instance. Such options may also be prefixed
with "default" in order to restore default settings regardless of what has been
specified in a previous "defaults" section.
keyword defaults frontend listen backend
----------------------+----------+----------+---------+---------
acl - X X X
appsession - - X X
backlog X X X -
balance X - X X
bind - X X -
bind-process X X X X
block - X X X
capture cookie - X X -
capture request header - X X -
capture response header - X X -
clitimeout X X X - (deprecated)
contimeout X - X X (deprecated)
cookie X - X X
default_backend - X X -
disabled X X X X
dispatch - - X X
enabled X X X X
errorfile X X X X
errorloc X X X X
errorloc302 X X X X
errorloc303 X X X X
fullconn X - X X
grace - X X X
http-check disable-on-404 X - X X
log X X X X
maxconn X X X -
mode X X X X
monitor fail - X X -
monitor-net X X X -
monitor-uri X X X -
[no] option abortonclose X - X X
[no] option accept-invalid-
http-request X X X -
[no] option accept-invalid-
http-response X - X X
[no] option allbackups X - X X
[no] option checkcache X - X X
[no] option clitcpka X X X -
[no] option contstats X X X -
[no] option dontlog-normal X X X -
[no] option dontlognull X X X -
[no] option forceclose X - X X
option forwardfor X X X X
option httpchk X - X X
[no] option httpclose X X X X
option httplog X X X X
[no] option http_proxy X X X X
[no] option log-separate-
errors X X X -
[no] option logasap X X X -
[no] option nolinger X X X X
option originalto X X X X
[no] option persist X - X X
[no] option redispatch X - X X
option smtpchk X - X X
[no] option splice-auto X X X X
[no] option splice-request X X X X
[no] option splice-response X X X X
[no] option srvtcpka X - X X
option ssl-hello-chk X - X X
[no] option tcp-smart-
accept X X X -
option tcpka X X X X
option tcplog X X X X
[no] option tcpsplice X X X X
[no] option transparent X - X X
persist rdp-cookie X - X X
rate-limit sessions X X X -
redirect - X X X
redisp X - X X (deprecated)
redispatch X - X X (deprecated)
reqadd - X X X
reqallow - X X X
reqdel - X X X
reqdeny - X X X
reqiallow - X X X
reqidel - X X X
reqideny - X X X
reqipass - X X X
reqirep - X X X
reqisetbe - X X X
reqitarpit - X X X
reqpass - X X X
reqrep - X X X
reqsetbe - X X X
reqtarpit - X X X
retries X - X X
rspadd - X X X
rspdel - X X X
rspdeny - X X X
rspidel - X X X
rspideny - X X X
rspirep - X X X
rsprep - X X X
server - - X X
source X - X X
srvtimeout X - X X (deprecated)
stats auth X - X X
stats enable X - X X
stats realm X - X X
stats refresh X - X X
stats scope X - X X
stats uri X - X X
stats hide-version X - X X
tcp-request content accept - X X -
tcp-request content reject - X X -
tcp-request inspect-delay - X X -
timeout check X - X X
timeout client X X X -
timeout clitimeout X X X - (deprecated)
timeout connect X - X X
timeout contimeout X - X X (deprecated)
timeout http-request X X X X
timeout queue X - X X
timeout server X - X X
timeout srvtimeout X - X X (deprecated)
timeout tarpit X X X X
transparent X - X X (deprecated)
use_backend - X X -
----------------------+----------+----------+---------+---------
keyword defaults frontend listen backend
4.2. Alphabetically sorted keywords reference
---------------------------------------------
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 sections : defaults | frontend | listen | backend
no | yes | yes | yes
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.
appsession <cookie> len <length> timeout <holdtime>
Define session stickiness on an existing application cookie.
May be used in sections : defaults | frontend | listen | backend
no | no | yes | yes
Arguments :
<cookie> this is the name of the cookie used by the application and which
HAProxy will have to learn for each new session.
<length> this is the number of characters that will be memorized and
checked in each cookie value.
<holdtime> this is the time after which the cookie will be removed from
memory if unused. If no unit is specified, this time is in
milliseconds.
When an application cookie is defined in a backend, HAProxy will check when
the server sets such a cookie, and will store its value in a table, and
associate it with the server's identifier. Up to <length> characters from
the value will be retained. On each connection, haproxy will look for this
cookie both in the "Cookie:" headers, and as a URL parameter in the query
string. If a known value is found, the client will be directed to the server
associated with this value. Otherwise, the load balancing algorithm is
applied. Cookies are automatically removed from memory when they have been
unused for a duration longer than <holdtime>.
The definition of an application cookie is limited to one per backend.
Example :
appsession JSESSIONID len 52 timeout 3h
See also : "cookie", "capture cookie" and "balance".
backlog <conns>
Give hints to the system about the approximate listen backlog desired size
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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.
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).
See also : "maxconn" and the target operating system's tuning guide.
balance <algorithm> [ <arguments> ]
balance url_param <param> [check_post [<max_wait>]]
Define the load balancing algorithm to be used in a backend.
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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.
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.
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 stickyness
to clients which refuse session cookies. This algorithm is
static, which means that changing a server's weight on the
fly will have no effect.
uri The left part of the URI (before the question mark) is hashed
and divided by the total weight of the running servers. The
result designates which server will receive the request. This
ensures that a 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, which means
that changing a server's weight on the fly will have no
effect.
This algorithm support 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.
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 the question mark indicating a query string ('?') is not
present in the URL. Optionally, specify a number of octets to
wait for before attempting to search the message body. If the
entity can not be searched, then round robin is used for each
request. For instance, if your clients always send the LB
parameter in the first 128 bytes, then specify that. The
default is 48. The entity data will not be scanned until the
required number of octets have arrived at the gateway, this
is the minimum of: (default/max_wait, Content-Length or first
chunk length). If Content-Length is missing or zero, it does
not need to wait for more data than the client promised to
send. When Content-Length is present and larger than
<max_wait>, then waiting is limited to <max_wait> and it is
assumed that this will be enough data to search for the
presence of the parameter. In the unlikely event that
Transfer-Encoding: chunked is used, only the first chunk is
scanned. Parameter values separated by a chunk boundary, may
be randomly balanced if at all.
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, which means that changing a
server's weight on the fly will have no effect.
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 round-robin
algorithm is applied instead.
An optionnal '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.
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 round-robind 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.
<arguments> is an optional list of arguments which may be needed by some
algorithms. Right now, only "url_param" and "uri" support an
optional argument.
balance uri [len <len>] [depth <depth>]
balance url_param <param> [check_post [<max_wait>]]
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.
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
Note: the following caveats and limitations on using the "check_post"
extension with "url_param" must be considered :
- all POST requests are eligable 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 reqideny 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 (RFC2616 3.6.1) 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. Scaning 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.
See also : "dispatch", "cookie", "appsession", "transparent" and "http_proxy".
bind [<address>]:<port> [, ...]
bind [<address>]:<port> [, ...] interface <interface>
bind [<address>]:<port> [, ...] mss <maxseg>
bind [<address>]:<port> [, ...] transparent
Define one or several listening addresses and/or ports in a frontend.
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | no
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".
<port> is the TCP port number the proxy will listen on. The port is
mandatory. Note that in the case of an IPv6 address, the port
is always the number after the last colon (':').
<interface> is an optional physical interface name. This is currently
only supported on Linux. The interface must be a physical
interface, not an aliased interface. When specified, all
addresses on the same line will only be accepted if the
incoming packet physically come through the designated
interface. It is also possible to bind multiple frontends to
the same address if they are bound to different interfaces.
Note that binding to a physical interface requires root
privileges.
<maxseg> is an optional TCP Maximum Segment Size (MSS) value to be
advertised on incoming connections. This can be used to force
a lower MSS for certain specific ports, for instance for
connections passing through a VPN. Note that this relies on a
kernel feature which is theorically supported under Linux but
was buggy in all versions prior to 2.6.28. It may or may not
work on other operating systems. The commonly advertised
value on Ethernet networks is 1460 = 1500(MTU) - 40(IP+TCP).
transparent is an optional keyword which is supported only on certain
Linux kernels. It indicates that the addresses will be bound
even if they do not belong to the local machine. Any packet
targetting any of these addresses will be caught just as if
the address was locally configured. This normally requires
that IP forwarding is enabled. Caution! do not use this with
the default address '*', as it would redirect any traffic for
the specified port. This keyword is available only when
HAProxy is built with USE_LINUX_TPROXY=1.
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
See also : "source".
bind-process [ all | odd | even | <number 1-32> ] ...
Limit visibility of an instance to a certain set of processes numbers.
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
all All process will see this instance. This is the default. It
may be used to override a default value.
odd This instance will be enabled on processes 1,3,5,...31. This
option may be combined with other numbers.
even This instance will be enabled on processes 2,4,6,...32. This
option may be combined with other numbers. Do not use it
with less than 2 processes otherwise some instances might be
missing from all processes.
number The instance will be enabled on this process number, between
1 and 32. You must be careful not to reference a process
number greater than the configured global.nbproc, otherwise
some instances might be missing from all processes.
This keyword limits binding of certain instances to certain processes. This
is useful in order not to have too many processes listening to the same
ports. For instance, on a dual-core machine, it might make sense to set
'nbproc 2' in the global section, then distributes the listeners among 'odd'
and 'even' instances.
At the moment, it is not possible to reference more than 32 processes using
this keyword, but this should be more than enough for most setups. Please
note that 'all' really means all processes and is not limited to the first
32.
If some backends are referenced by frontends bound to other processes, the
backend automatically inherits the frontend's processes.
Example :
listen app_ip1
bind 10.0.0.1:80
bind_process odd
listen app_ip2
bind 10.0.0.2:80
bind_process even
listen management
bind 10.0.0.3:80
bind_process 1 2 3 4
See also : "nbproc" in global section.
block { if | unless } <condition>
Block a layer 7 request if/unless a condition is matched
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
The HTTP request will be blocked very early in the layer 7 processing
if/unless <condition> is matched. A 403 error will be returned if the request
is blocked. The condition has to reference ACLs (see section 7). This is
typically used to deny access to certain sensible resources if some
conditions are met or not met. There is no fixed limit to the number of
"block" statements per instance.
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
block if invalid_src || local_dst
See section 7 about ACL usage.
capture cookie <name> len <length>
Capture and log a cookie in the request and in the response.
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | no
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 (eg: ASPSESSIONXXXXX).
<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
configured in the souces by default to 64 characters. It is not possible to
specify a capture in a "defaults" section.
Example:
capture cookie ASPSESSION len 32
See also : "capture request header", "capture response header" as well as
section 8 about logging.
capture request header <name> len <length>
Capture and log the first occurrence of the specified request header.
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | no
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>.
Only the first 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
differenciate 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, but each capture
is limited to 64 characters. 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 Referrer len 15
See also : "capture cookie", "capture response header" as well as section 8
about logging.
capture response header <name> len <length>
Capture and log the first occurrence of the specified response header.
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | no
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>.
Only the first 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, but each
capture is limited to 64 characters. 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
See also : "capture cookie", "capture request header" as well as section 8
about logging.
clitimeout <timeout>
Set the maximum inactivity time on the client side.
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
Arguments :
<timeout> is the timeout value is 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. 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
(eg: 4 or 5 seconds).
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 results in accumulation of expired sessions in
the system if the system's timeouts are not configured either.
This parameter is provided for compatibility but is currently deprecated.
Please use "timeout client" instead.
See also : "timeout client", "timeout http-request", "timeout server", and
"srvtimeout".
contimeout <timeout>
Set the maximum time to wait for a connection attempt to a server to succeed.
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
Arguments :
<timeout> is the timeout value is 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 (eg: 4 or 5 seconds). By default, the
connect timeout also presets the queue timeout to the same value if this one
has not been specified. Historically, the contimeout was also used to set the
tarpit timeout in a listen section, which is not possible in a pure frontend.
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 results in accumulation of failed sessions in
the system if the system's timeouts are not configured either.
This parameter is provided for backwards compatibility but is currently
deprecated. Please use "timeout connect", "timeout queue" or "timeout tarpit"
instead.
See also : "timeout connect", "timeout queue", "timeout tarpit",
"timeout server", "contimeout".
cookie <name> [ rewrite | insert | prefix ] [ indirect ] [ nocache ]
[ postonly ] [ domain <domain> ]
Enable cookie-based persistence in a backend.
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 (eg:
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 only
works in HTTP close mode. Unless the application behaviour 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 the responses. If the server emits a
cookie with the same name, it will be replaced anyway. 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. Due to
caching effects, it is generally wise to add the "indirect" and
"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 requires the HTTP close mode. The "prefix" keyword is
not compatible with "rewrite" and "insert".
indirect When this option is specified in insert mode, cookies will only
be added when the server was not reached after a direct access,
which means that only when a server is elected after applying a
load-balancing algorithm, or after a redispatch, then the cookie
will be inserted. If the client has all the required information
to connect to the same server next time, no further cookie will
be inserted. In all cases, when the "indirect" option is used in
insert mode, the cookie is always removed from the requests
transmitted to the server. The persistence mechanism then becomes
totally transparent from the application point of view.
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.
domain This option allows to specify the domain at which a cookie is
inserted. It requires exactly one paramater: a valid domain
name.
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
See also : "appsession", "balance source", "capture cookie", "server".
default_backend <backend>
Specify the backend to use when no "use_backend" rule has been matched.
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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
See also : "use_backend", "reqsetbe", "reqisetbe"
disabled
Disable a proxy, frontend or backend.
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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.
See also : "enabled"
enabled
Enable a proxy, frontend or backend.
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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.
See also : "disabled"
errorfile <code> <file>
Return a file contents instead of errors generated by HAProxy
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 400, 403, 408, 500, 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.
The files are returned verbatim on the TCP socket. This allows any trick such
as redirections to another URL or site, as well as tricks to clean cookies,
force enable or disable caching, etc... The package provides default error
files returning the same contents as default errors.
The files should not exceed the configured buffer size (BUFSIZE), which
generally is 8 or 16 kB, otherwise they will be truncated. It is also wise
not to put any reference to local contents (eg: 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. For better HTTP compliance, it is
recommended that all header lines end with CR-LF and not LF alone.
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.
See also : "errorloc", "errorloc302", "errorloc303"
Example :
errorfile 400 /etc/haproxy/errorfiles/400badreq.http
errorfile 403 /etc/haproxy/errorfiles/403forbid.http
errorfile 503 /etc/haproxy/errorfiles/503sorry.http
errorloc <code> <url>
errorloc302 <code> <url>
Return an HTTP redirection to a URL instead of errors generated by HAProxy
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 400, 403, 408, 500, 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 (eg: 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.
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
workaround 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.
See also : "errorfile", "errorloc303"
errorloc303 <code> <url>
Return an HTTP redirection to a URL instead of errors generated by HAProxy
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 400, 403, 408, 500, 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 (eg: 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.
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.
See also : "errorfile", "errorloc", "errorloc302"
fullconn <conns>
Specify at what backend load the servers will reach their maxconn
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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
exceptionnal loads.
Example :
# The servers will accept between 100 and 1000 concurrent connections each
# and the maximum of 1000 will be reached when the backend reaches 10000
# connections.
backend dynamic
fullconn 10000
server srv1 dyn1:80 minconn 100 maxconn 1000
server srv2 dyn2:80 minconn 100 maxconn 1000
See also : "maxconn", "server"
grace <time>
Maintain a proxy operational for some time after a soft stop
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<time> is the time (by default in milliseconds) for which the instance
will remain operational with the frontend sockets still listening
when a soft-stop is received via the SIGUSR1 signal.
This may be used to ensure that the services disappear in a certain order.
This was designed so that frontends which are dedicated to monitoring by an
external equipement fail immediately while other ones remain up for the time
needed by the equipment to detect the failure.
Note that currently, there is very little benefit in using this parameter,
and it may in fact complicate the soft-reconfiguration process more than
simplify it.
http-check disable-on-404
Enable a maintenance mode upon HTTP/404 response to health-checks
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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.
See also : "option httpchk"
id <value>
Set a persistent value for proxy ID. Must be unique and larger than 1000, as
smaller values are reserved for auto-assigned ids.
log global
log <address> <facility> [<level> [<minlevel>]]
Enable per-instance logging of events and traffic.
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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 <address>, <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.
<address> 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).
- 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 writeable).
<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
<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
Note that up to two "log" entries may be specified per instance. However, if
"log global" is used and if the "global" section already contains 2 log
entries, then additional log entries will be ignored.
Also, 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 127.0.0.1:514 local0 notice # only send important events
log 127.0.0.1:514 local0 notice notice # same but limit output level
maxconn <conns>
Fix the maximum number of concurrent connections on a frontend
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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 8kB each, as well as some other data resulting in about 17 kB of RAM being
consumed per established connection. That means that a medium system equipped
with 1GB of RAM can withstand around 40000-50000 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.
See also : "server", global section's "maxconn", "fullconn"
mode { tcp|http|health }
Set the running mode or protocol of the instance
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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.
health The instance will work in "health" mode. It will just reply "OK"
to incoming connections and close the connection. Nothing will be
logged. This mode is used to reply to external components health
checks. This mode is deprecated and should not be used anymore as
it is possible to do the same and even better by combining TCP or
HTTP modes with the "monitor" keyword.
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
See also : "monitor", "monitor-net"
monitor fail [if | unless] <condition>
Add a condition to report a failure to a monitor HTTP request.
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | no
Arguments :
if <cond> the monitor request will fail if the condition is satisfied,
and will succeed otherwise. The condition should describe a
combinated 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.
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
See also : "monitor-net", "monitor-uri"
monitor-net <source>
Declare a source network which is limited to monitor requests
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
Arguments :
<source> is the source IPv4 address or network which will only be able to
get monitor responses to any request. It can be either an IPv4
address, a host name, or an address followed by a slash ('/')
followed by a mask.
In TCP mode, any connection coming from a source matching <source> will cause
the connection to be immediately closed without any log. This allows another
equipement to probe the port and verify that it is still listening, without
forwarding the connection to a remote server.
In HTTP mode, a connection coming from a source matching <source> will be
accepted, the following response will be sent without waiting for a request,
then the connection will be closed : "HTTP/1.0 200 OK". 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.
Monitor requests are processed very early. It is not possible to block nor
divert them using ACLs. They cannot be logged either, and it is the intended
purpose. They are only used to report HAProxy's health to an upper component,
nothing more. Right now, it is not possible to set failure conditions on
requests caught by "monitor-net".
Example :
# addresses .252 and .253 are just probing us.
frontend www
monitor-net 192.168.0.252/31
See also : "monitor fail", "monitor-uri"
monitor-uri <uri>
Intercept a URI used by external components' monitor requests
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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. It is not possible to block nor
divert them using ACLs. They cannot be logged either, and it is the intended
purpose. 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).
Example :
# Use /haproxy_test to report haproxy's status
frontend www
mode http
monitor-uri /haproxy_test
See also : "monitor fail", "monitor-net"
option abortonclose
no option abortonclose
Enable or disable early dropping of aborted requests pending in queues.
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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-session
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 session while waiting for the response. Some HTTP agents
support this behaviour (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 session early while
still not served and not pollute the servers.
In HAProxy, the user can choose the desired behaviour using the option
"abortonclose". By default (without the option) the behaviour is HTTP
compliant and aborted requests will be served. But when the option is
specified, a session 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.
See also : "timeout queue" and server's "maxconn" and "maxqueue" parameters
option accept-invalid-http-request
no option accept-invalid-http-request
Enable or disable relaxing of HTTP request parsing
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
Arguments : none
By default, HAProxy complies with RFC2616 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 behaviour 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 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. 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.
See also : "option accept-invalid-http-response" and "show errors" on the
stats socket.
option accept-invalid-http-response
no option accept-invalid-http-response
Enable or disable relaxing of HTTP response parsing
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
Arguments : none
By default, HAProxy complies with RFC2616 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 behaviour 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 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.
See also : "option accept-invalid-http-request" and "show errors" on the
stats socket.
option allbackups
no option allbackups
Use either all backup servers at a time or only the first one
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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.
option checkcache
no option checkcache
Analyze all server responses and block requests with cachable cookies
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 cachable 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 sensible 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 cachability. 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, 206, 300, 301, 410,
provided that the server has not set a "Cache-control: public" header ;
- all those that come from a POST request, provided that the server has not
set a 'Cache-Control: public' header ;
- 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 "rspdeny" filter, with an "HTTP 502 bad gateway".
The session state shows "PH--" meaning that the proxy blocked the response
during headers processing. Additionnaly, 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 behaviours.
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 clitcpka
no option clitcpka
Enable or disable the sending of TCP keepalive packets on the client side
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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 (eg: 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.
See also : "option srvtcpka", "option tcpka"
option contstats
Enable continuous traffic statistics updates
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
Arguments : none
By default, counters used for statistics calculation are incremented
only when a session 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 continuously,
during a whole session. Recounting touches a hotpath directly so
it is not enabled by default, as it has small performance impact (~0.5%).
option dontlog-normal
no option dontlog-normal
Enable or disable logging of normal, successful connections
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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.
See also : "log", "dontlognull", "log-separate-errors" and section 8 about
logging.
option dontlognull
no option dontlognull
Enable or disable logging of null connections
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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.
It is generally recommended not to use this option in uncontrolled
environments (eg: 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.
See also : "log", "monitor-net", "monitor-uri" and section 8 about logging.
option forceclose
no option forceclose
Enable or disable active connection closing after response is transferred.
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
Arguments : none
Some HTTP servers do not necessarily close the connections when they receive
the "Connection: close" set by "option httpclose", and if the client does not
close either, then the connection remains open till the timeout expires. This
causes high number of simultaneous connections on the servers and shows high
global session times in the logs.
When this happens, it is possible to use "option forceclose". It will
actively close the outgoing server channel as soon as the server begins to
reply and only if the request buffer is empty. Note that this should NOT be
used if CONNECT requests are expected between the client and the server. This
option implicitly enables the "httpclose" option.
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.
See also : "option httpclose"
option forwardfor [ except <network> ] [ header <name> ]
Enable insertion of the X-Forwarded-For header to requests sent to servers
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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 (eg: stunnel),
and you need preserve it. Also if your backend server doesn't use the
"X-Forwarded-For" header and requires different one (eg: 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.
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.
It is important to note that as long as HAProxy does not support keep-alive
connections, only the first request of a connection will receive the header.
For this reason, it is important to ensure that "option httpclose" is set
when using this option.
Examples :
# Public HTTP address also used by stunnel on the same machine
frontend www
mode http
option forwardfor except 127.0.0.1 # stunnel already adds the header
# Those servers want the IP Address in X-Client
backend www
mode http
option forwardfor header X-Client
See also : "option httpclose"
option httpchk
option httpchk <uri>
option httpchk <method> <uri>
option httpchk <method> <uri> <version>
Enable HTTP protocol to check on the servers health
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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, and as a trick, it is possible to pass it
after "\r\n" following the version string.
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.
The port and interval are specified in the server configuration.
This 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.
Examples :
# Relay HTTPS traffic to Apache instance and check service availability
# using HTTP request "OPTIONS * HTTP/1.1" on port 80.
backend https_relay
mode tcp
option httpchk OPTIONS * HTTP/1.1\r\nHost:\ www
server apache1 192.168.1.1:443 check port 80
See also : "option ssl-hello-chk", "option smtpchk", "http-check" and the
"check", "port" and "interval" server options.
option httpclose
no option httpclose
Enable or disable passive HTTP connection closing
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments : none
As stated in section 1, HAProxy does not yes support the HTTP keep-alive
mode. So by default, if a client communicates with a server in this mode, it
will only analyze, log, and process the first request of each connection. To
workaround this limitation, it is possible to specify "option httpclose". It
will check if a "Connection: close" header is already set in each direction,
and will add one if missing. Each end should react to this by actively
closing the TCP connection after each transfer, thus resulting in a switch to
the HTTP close mode. Any "Connection" header different from "close" will also
be removed.
It seldom happens that some servers incorrectly ignore this header and do not
close the connection eventough they reply "Connection: close". For this
reason, they are not compatible with older HTTP 1.0 browsers. If this
happens it is possible to use the "option forceclose" which actively closes
the request connection once the server responds.
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.
If "option forceclose" is specified too, it has precedence over "httpclose".
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.
See also : "option forceclose"
option httplog [ clf ]
Enable logging of HTTP request, session state and timers
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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 analyser 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 session
status, the connections numbers, the captured headers and cookies, the
frontend, backend and server name, and of course the source address and
ports.
This option may be set either in the frontend or the backend.
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. Specifying
only "option httplog" will automatically clear the 'clf' mode if it was set
by default.
See also : section 8 about logging.
option http_proxy
no option http_proxy
Enable or disable plain HTTP proxy mode
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments : none
It sometimes happens that people need a pure HTTP proxy which understands
basic proxy requests without caching nor any fancy feature. In this case,
it may be worth setting up an HAProxy instance with the "option http_proxy"
set. In this mode, no server is declared, and the connection is forwarded to
the IP address and port found in the URL after the "http://" scheme.
No host address resolution is performed, so this only works when pure IP
addresses are passed. Since this option's usage perimeter is rather limited,
it will probably be used only by experts who know they need exactly it. Last,
if the clients are susceptible of sending keep-alive requests, it will be
needed to add "option http_close" to ensure that all requests will correctly
be analyzed.
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.
Example :
# this backend understands HTTP proxy requests and forwards them directly.
backend direct_forward
option httpclose
option http_proxy
See also : "option httpclose"
option log-separate-errors
no option log-separate-errors
Change log level for non-completely successful connections
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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.
See also : "log", "dontlognull", "dontlog-normal" and section 8 about
logging.
option logasap
no option logasap
Enable or disable early logging of HTTP requests
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
Arguments : none
By default, HTTP requests are logged upon termination so that the total
transfer time and the number of bytes appear in the logs. When large objects
are being transferred, it may take a while before the request appears in the
logs. Using "option logasap", the request gets logged as soon as the server
sends the complete headers. The only missing information in the logs will be
the total number of bytes which will indicate everything except the amount
of data transferred, and the total time which will not take the transfer
time into account. In such a situation, it's a 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"
See also : "option httplog", "capture response header", and section 8 about
logging.
option nolinger
no option nolinger
Enable or disable immediate session ressource cleaning after close
May be used in sections: defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments : none
When clients or servers abort connections in a dirty way (eg: 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,
the session is instantly purged from the system's tables. This usually has
side effects such as increased number of TCP resets due to old retransmits
getting immediately rejected. Some firewalls may sometimes complain about
this too.
For this reason, it is not recommended to use this option when not absolutely
needed. You know that you need it when you have thousands of FIN_WAIT1
sessions on your system (TIME_WAIT ones do not count).
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.
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 originalto [ except <network> ] [ header <name> ]
Enable insertion of the X-Original-To header to requests sent to servers
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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 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.
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.
It is important to note that as long as HAProxy does not support keep-alive
connections, only the first request of a connection will receive the header.
For this reason, it is important to ensure that "option httpclose" is set
when using this option.
Examples :
# Original Destination address
frontend www
mode http
option originalto except 127.0.0.1
# Those servers want the IP Address in X-Client-Dst
backend www
mode http
option originalto header X-Client-Dst
See also : "option httpclose"
option persist
no option persist
Enable or disable forced persistence on down servers
May be used in sections: defaults | frontend | listen | backend
yes | no | yes | yes
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.
See also : "option redispatch", "retries"
option redispatch
no option redispatch
Enable or disable session redistribution in case of connection failure
May be used in sections: defaults | frontend | listen | backend
yes | no | yes | yes
Arguments : none
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 their
persistence and redistribute them to a working server.
It also allows to retry last connection to another server in case of multiple
connection failures. Of course, it requires having "retries" set to a nonzero
value.
This form is the preferred form, which replaces both the "redispatch" and
"redisp" keywords.
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.
See also : "redispatch", "retries"
option smtpchk
option smtpchk <hello> <domain>
Use SMTP health checks for server testing
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
Arguments :
<hello> is an optional argument. It is the "hello" command to use. It can
be either "HELO" (for SMTP) or "EHLO" (for ESTMP). 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 behaviour. 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 cttproxy feature to be compiled in.
Example :
option smtpchk HELO mydomain.org
See also : "option httpchk", "source"
option splice-auto
no option splice-auto
Enable or disable automatic kernel acceleration on sockets in both directions
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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 independantly. 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.
See also : "option splice-request", "option splice-response", and global
options "nosplice" and "maxpipes"
option splice-request
no option splice-request
Enable or disable automatic kernel acceleration on sockets for requests
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments : none
When this option is enabled either on a frontend or on a backend, haproxy
will user 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.
See also : "option splice-auto", "option splice-response", and global options
"nosplice" and "maxpipes"
option splice-response
no option splice-response
Enable or disable automatic kernel acceleration on sockets for responses
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments : none
When this option is enabled either on a frontend or on a backend, haproxy
will user 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.
See also : "option splice-auto", "option splice-request", and global options
"nosplice" and "maxpipes"
option srvtcpka
no option srvtcpka
Enable or disable the sending of TCP keepalive packets on the server side
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 (eg: 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.
See also : "option clitcpka", "option tcpka"
option ssl-hello-chk
Use SSLv3 client hello health checks for server testing
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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.
See also: "option httpchk"
option tcp-smart-accept
no option tcp-smart-accept
Enable or disable the saving of one ACK packet during the accept sequence
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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 behaviour 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.
See also : "option tcp-smart-connect"
option tcp-smart-connect
no option tcp-smart-connect
Enable or disable the saving of one ACK packet during the connect sequence
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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.
See also : "option tcp-smart-accept"
option tcpka
Enable or disable the sending of TCP keepalive packets on both sides
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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 (eg: 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.
See also : "option clitcpka", "option srvtcpka"
option tcplog
Enable advanced logging of TCP connections with session state and timers
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
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 session 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.
This option may be set either in the frontend or the backend.
See also : "option httplog", and section 8 about logging.
option tcpsplice [ experimental ]
Enable linux kernel-based acceleration of data relaying
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments : none
This option is only available when HAProxy has been built for use on Linux
with USE_TCPSPLICE=1. This option requires a kernel patch which is available
on http://www.linux-l7sw.org/.
When "option tcpsplice" is set, as soon as the server's response headers have
been transferred, the session handling is transferred to the kernel which
will forward all subsequent data from the server to the client untill the
session closes. This leads to much faster data transfers between client and
server since the data is not copied twice between kernel and user space, but
there are some limitations such as the lack of information about the number
of bytes transferred and the total transfer time.
This is an experimental feature. It happens to reliably work but issues
caused by corner cases are to be expected.
Note that this option requires that the process permanently runs with
CAP_NETADMIN privileges, which most often translates into running as root.
option transparent
no option transparent
Enable client-side transparent proxying
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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.
See also: the "usersrc" argument of the "source" keyword, and the
"transparent" option of the "bind" keyword.
persist rdp-cookie
persist rdp-cookie(name)
Enable RDP cookie-based persistence
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
Arguments :
<name> is the optional name of the RDP cookie to check. If omitted, the
default cookie name "mstshash" 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 analysed
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 higly recommended to put all statements in
a single "listen" section.
Example :
listen tse-farm
bind :3389
# wait up to 5s for an RDP cookie in the request
tcp-request inspect-delay 5s
tcp-request content accept if RDP_COOKIE
# apply RDP cookie persistence
persist rdp-cookie
# if server is unknown, let's balance on the same cookie.
# alternatively, "balance leastconn" may be useful too.
balance rdp-cookie
server srv1 1.1.1.1:3389
server srv2 1.1.1.2:3389
See also : "balance rdp-cookie", "tcp-request" and the "req_rdp_cookie" ACL.
rate-limit sessions <rate>
Set a limit on the number of new sessions accepted per second on a frontend
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | no
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 127.0.0.1:1025
Note : when the maximum rate is reached, the frontend's status appears as
"FULL" in the statistics, exactly as when it is saturated.
See also : the "backlog" keyword and the "fe_sess_rate" ACL criterion.
redirect location <to> [code <code>] <option> {if | unless} <condition>
redirect prefix <to> [code <code>] <option> {if | unless} <condition>
Return an HTTP redirection if/unless a condition is matched
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
If/unless the condition is matched, the HTTP request will lead to a redirect
response.
Arguments :
<to> With "redirect location", the exact value in <to> is placed into
the HTTP "Location" header. In case of "redirect prefix", the
"Location" header is built from the concatenation of <to> and the
complete URI, including the query string, unless the "drop-query"
option is specified (see below). As a special case, if <to>
equals exactly "/" in prefix mode, then nothing is inserted
before the original URI. It allows one to redirect to the same
URL.
<code> The code is optional. It indicates which type of HTTP redirection
is desired. Only codes 301, 302 and 303 are supported, and 302 is
used if no code is specified. 301 means "Moved permanently", and
a browser may cache the Location. 302 means "Moved permanently"
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.
<option> There are several options which can be specified to adjust the
expected behaviour 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.
- "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
See section 7 about ACL usage.
redisp (deprecated)
redispatch (deprecated)
Enable or disable session redistribution in case of connection failure
May be used in sections: defaults | frontend | listen | backend
yes | no | yes | yes
Arguments : none
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 "redispatch" will allow the proxy to break their persistence and
redistribute them to a working server.
It also allows to retry last connection to another server in case of multiple
connection failures. Of course, it requires having "retries" set to a nonzero
value.
This form is deprecated, do not use it in any new configuration, use the new
"option redispatch" instead.
See also : "option redispatch"
reqadd <string>
Add a header at the end of the HTTP request
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<string> is the complete line to be added. Any space or known delimiter
must be escaped using a backslash ('\'). Please refer to section
6 about HTTP header manipulation for more information.
A new line consisting in <string> followed by a line feed will be added after
the last header of an HTTP request.
Header transformations only apply to traffic which passes through HAProxy,
and not to traffic generated by HAProxy, such as health-checks or error
responses.
See also: "rspadd" and section 6 about HTTP header manipulation
reqallow <search>
reqiallow <search> (ignore case)
Definitely allow an HTTP request if a line matches a regular expression
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The
"reqallow" keyword strictly matches case while "reqiallow"
ignores case.
A request containing any line which matches extended regular expression
<search> will mark the request as allowed, even if any later test would
result in a deny. The test applies both to the request line and to request
headers. Keep in mind that URLs in request line are case-sensitive while
header names are not.
It is easier, faster and more powerful to use ACLs to write access policies.
Reqdeny, reqallow and reqpass should be avoided in new designs.
Example :
# allow www.* but refuse *.local
reqiallow ^Host:\ www\.
reqideny ^Host:\ .*\.local
See also: "reqdeny", "acl", "block" and section 6 about HTTP header
manipulation
reqdel <search>
reqidel <search> (ignore case)
Delete all headers matching a regular expression in an HTTP request
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The "reqdel"
keyword strictly matches case while "reqidel" ignores case.
Any header line matching extended regular expression <search> in the request
will be completely deleted. Most common use of this is to remove unwanted
and/or dangerous headers or cookies from a request before passing it to the
next servers.
Header transformations only apply to traffic which passes through HAProxy,
and not to traffic generated by HAProxy, such as health-checks or error
responses. Keep in mind that header names are not case-sensitive.
Example :
# remove X-Forwarded-For header and SERVER cookie
reqidel ^X-Forwarded-For:.*
reqidel ^Cookie:.*SERVER=
See also: "reqadd", "reqrep", "rspdel" and section 6 about HTTP header
manipulation
reqdeny <search>
reqideny <search> (ignore case)
Deny an HTTP request if a line matches a regular expression
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The
"reqdeny" keyword strictly matches case while "reqideny" ignores
case.
A request containing any line which matches extended regular expression
<search> will mark the request as denied, even if any later test would
result in an allow. The test applies both to the request line and to request
headers. Keep in mind that URLs in request line are case-sensitive while
header names are not.
A denied request will generate an "HTTP 403 forbidden" response once the
complete request has been parsed. This is consistent with what is practiced
using ACLs.
It is easier, faster and more powerful to use ACLs to write access policies.
Reqdeny, reqallow and reqpass should be avoided in new designs.
Example :
# refuse *.local, then allow www.*
reqideny ^Host:\ .*\.local
reqiallow ^Host:\ www\.
See also: "reqallow", "rspdeny", "acl", "block" and section 6 about HTTP
header manipulation
reqpass <search>
reqipass <search> (ignore case)
Ignore any HTTP request line matching a regular expression in next rules
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The
"reqpass" keyword strictly matches case while "reqipass" ignores
case.
A request containing any line which matches extended regular expression
<search> will skip next rules, without assigning any deny or allow verdict.
The test applies both to the request line and to request headers. Keep in
mind that URLs in request line are case-sensitive while header names are not.
It is easier, faster and more powerful to use ACLs to write access policies.
Reqdeny, reqallow and reqpass should be avoided in new designs.
Example :
# refuse *.local, then allow www.*, but ignore "www.private.local"
reqipass ^Host:\ www.private\.local
reqideny ^Host:\ .*\.local
reqiallow ^Host:\ www\.
See also: "reqallow", "reqdeny", "acl", "block" and section 6 about HTTP
header manipulation
reqrep <search> <string>
reqirep <search> <string> (ignore case)
Replace a regular expression with a string in an HTTP request line
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The "reqrep"
keyword strictly matches case while "reqirep" ignores case.
<string> is the complete line to be added. Any space or known delimiter
must be escaped using a backslash ('\'). References to matched
pattern groups are possible using the common \N form, with N
being a single digit between 0 and 9. Please refer to section
6 about HTTP header manipulation for more information.
Any line matching extended regular expression <search> in the request (both
the request line and header lines) will be completely replaced with <string>.
Most common use of this is to rewrite URLs or domain names in "Host" headers.
Header transformations only apply to traffic which passes through HAProxy,
and not to traffic generated by HAProxy, such as health-checks or error
responses. Note that for increased readability, it is suggested to add enough
spaces between the request and the response. Keep in mind that URLs in
request line are case-sensitive while header names are not.
Example :
# replace "/static/" with "/" at the beginning of any request path.
reqrep ^([^\ ]*)\ /static/(.*) \1\ /\2
# replace "www.mydomain.com" with "www" in the host name.
reqirep ^Host:\ www.mydomain.com Host:\ www
See also: "reqadd", "reqdel", "rsprep" and section 6 about HTTP header
manipulation
reqtarpit <search>
reqitarpit <search> (ignore case)
Tarpit an HTTP request containing a line matching a regular expression
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<search> is the regular expression applied to HTTP headers and to the
request line. This is an extended regular expression. Parenthesis
grouping is supported and no preliminary backslash is required.
Any space or known delimiter must be escaped using a backslash
('\'). The pattern applies to a full line at a time. The
"reqtarpit" keyword strictly matches case while "reqitarpit"
ignores case.
A request containing any line which matches extended regular expression
<search> will be tarpitted, which means that it will connect to nowhere, will
be kept open for a pre-defined time, then will return an HTTP error 500 so
that the attacker does not suspect it has been tarpitted. The status 500 will
be reported in the logs, but the completion flags will indicate "PT". The
delay is defined by "timeout tarpit", or "timeout connect" if the former is
not set.
The goal of the tarpit is to slow down robots attacking servers with
identifiable requests. Many robots limit their outgoing number of connections
and stay connected waiting for a reply which can take several minutes to
come. Depending on the environment and attack, it may be particularly
efficient at reducing the load on the network and firewalls.
Example :
# ignore user-agents reporting any flavour of "Mozilla" or "MSIE", but
# block all others.
reqipass ^User-Agent:\.*(Mozilla|MSIE)
reqitarpit ^User-Agent:
See also: "reqallow", "reqdeny", "reqpass", and section 6 about HTTP header
manipulation
retries <value>
Set the number of retries to perform on a server after a connection failure
May be used in sections: defaults | frontend | listen | backend
yes | no | yes | yes
Arguments :
<value> is the number of times a connection attempt should be retried on
a server when a connection either is refused or times out. The
default value is 3.
It is important to understand that this value applies to the number of
connection attempts, not full requests. When a connection has effectively
been established to a server, there will be no more retry.
In order to avoid immediate reconnections to a server which is restarting,
a turn-around timer of 1 second is applied before a retry occurs.
When "option redispatch" is set, the last retry may be performed on another
server even if a cookie references a different server.
See also : "option redispatch"
rspadd <string>
Add a header at the end of the HTTP response
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<string> is the complete line to be added. Any space or known delimiter
must be escaped using a backslash ('\'). Please refer to section
6 about HTTP header manipulation for more information.
A new line consisting in <string> followed by a line feed will be added after
the last header of an HTTP response.
Header transformations only apply to traffic which passes through HAProxy,
and not to traffic generated by HAProxy, such as health-checks or error
responses.
See also: "reqadd" and section 6 about HTTP header manipulation
rspdel <search>
rspidel <search> (ignore case)
Delete all headers matching a regular expression in an HTTP response
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<search> is the regular expression applied to HTTP headers and to the
response line. This is an extended regular expression, so
parenthesis grouping is supported and no preliminary backslash
is required. Any space or known delimiter must be escaped using
a backslash ('\'). The pattern applies to a full line at a time.
The "rspdel" keyword strictly matches case while "rspidel"
ignores case.
Any header line matching extended regular expression <search> in the response
will be completely deleted. Most common use of this is to remove unwanted
and/or sensible headers or cookies from a response before passing it to the
client.
Header transformations only apply to traffic which passes through HAProxy,
and not to traffic generated by HAProxy, such as health-checks or error
responses. Keep in mind that header names are not case-sensitive.
Example :
# remove the Server header from responses
reqidel ^Server:.*
See also: "rspadd", "rsprep", "reqdel" and section 6 about HTTP header
manipulation
rspdeny <search>
rspideny <search> (ignore case)
Block an HTTP response if a line matches a regular expression
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<search> is the regular expression applied to HTTP headers and to the
response line. This is an extended regular expression, so
parenthesis grouping is supported and no preliminary backslash
is required. Any space or known delimiter must be escaped using
a backslash ('\'). The pattern applies to a full line at a time.
The "rspdeny" keyword strictly matches case while "rspideny"
ignores case.
A response containing any line which matches extended regular expression
<search> will mark the request as denied. The test applies both to the
response line and to response headers. Keep in mind that header names are not
case-sensitive.
Main use of this keyword is to prevent sensitive information leak and to
block the response before it reaches the client. If a response is denied, it
will be replaced with an HTTP 502 error so that the client never retrieves
any sensitive data.
It is easier, faster and more powerful to use ACLs to write access policies.
Rspdeny should be avoided in new designs.
Example :
# Ensure that no content type matching ms-word will leak
rspideny ^Content-type:\.*/ms-word
See also: "reqdeny", "acl", "block" and section 6 about HTTP header
manipulation
rsprep <search> <string>
rspirep <search> <string> (ignore case)
Replace a regular expression with a string in an HTTP response line
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<search> is the regular expression applied to HTTP headers and to the
response line. This is an extended regular expression, so
parenthesis grouping is supported and no preliminary backslash
is required. Any space or known delimiter must be escaped using
a backslash ('\'). The pattern applies to a full line at a time.
The "rsprep" keyword strictly matches case while "rspirep"
ignores case.
<string> is the complete line to be added. Any space or known delimiter
must be escaped using a backslash ('\'). References to matched
pattern groups are possible using the common \N form, with N
being a single digit between 0 and 9. Please refer to section
6 about HTTP header manipulation for more information.
Any line matching extended regular expression <search> in the response (both
the response line and header lines) will be completely replaced with
<string>. Most common use of this is to rewrite Location headers.
Header transformations only apply to traffic which passes through HAProxy,
and not to traffic generated by HAProxy, such as health-checks or error
responses. Note that for increased readability, it is suggested to add enough
spaces between the request and the response. Keep in mind that header names
are not case-sensitive.
Example :
# replace "Location: 127.0.0.1:8080" with "Location: www.mydomain.com"
rspirep ^Location:\ 127.0.0.1:8080 Location:\ www.mydomain.com
See also: "rspadd", "rspdel", "reqrep" and section 6 about HTTP header
manipulation
server <name> <address>[:port] [param*]
Declare a server in a backend
May be used in sections : defaults | frontend | listen | backend
no | no | yes | yes
Arguments :
<name> is the internal name assigned to this server. This name will
appear in logs and alerts.
<address> is the IPv4 address of the server. Alternatively, a resolvable
hostname is supported, but this name will be resolved during
start-up.
<ports> 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
See also : section 5 about server options
source <addr>[:<port>] [usesrc { <addr2>[:<port2>] | client | clientip } ]
source <addr>[:<port>] [interface <name>]
Set the source address for outgoing connections
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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.
<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.
<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.
Note that depending on the transparent proxy technology used, it may be
required to force the source address. In fact, cttproxy version 2 requires an
IP address in <addr> above, and does not support setting of "0.0.0.0" as the
IP address because it creates NAT entries which much match the exact outgoing
address. Tproxy version 4 and some other kernel patches which work in pure
forwarding mode generally will not have this limitation.
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.
Examples :
backend private
# Connect to the servers using our 192.168.1.200 source address
source 192.168.1.200
backend transparent_ssl1
# Connect to the SSL farm from the client's source address
source 192.168.1.200 usesrc clientip
backend transparent_ssl2
# Connect to the SSL farm from the client's source address and port
# not recommended if IP conntrack is present on the local machine.
source 192.168.1.200 usesrc client
backend transparent_ssl3
# Connect to the SSL farm from the client's source address. It
# is more conntrack-friendly.
source 192.168.1.200 usesrc clientip
backend transparent_smtp
# Connect to the SMTP farm from the client's source address/port
# with Tproxy version 4.
source 0.0.0.0 usesrc clientip
See also : the "source" server option in section 5, the Tproxy patches for
the Linux kernel on www.balabit.com, the "bind" keyword.
srvtimeout <timeout> (deprecated)
Set the maximum inactivity time on the server side.
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 (eg: 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. 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 results in accumulation of expired sessions in
the system if the system's timeouts are not configured either.
This parameter is provided for compatibility but is currently deprecated.
Please use "timeout server" instead.
See also : "timeout server", "timeout client" and "clitimeout".
stats auth <user>:<passwd>
Enable statistics with authentication and grant access to an account
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 sensible 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 :
# public access (limited to this backend only)
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
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "stats enable", "stats realm", "stats scope", "stats uri"
stats enable
Enable statistics reporting with default settings
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 :
# public access (limited to this backend only)
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
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "stats auth", "stats realm", "stats uri"
stats realm <realm>
Enable statistics and set authentication realm
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 :
# public access (limited to this backend only)
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
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "stats auth", "stats enable", "stats uri"
stats refresh <delay>
Enable statistics with automatic refresh
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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
he wants 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 :
# public access (limited to this backend only)
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
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "stats auth", "stats enable", "stats realm", "stats uri"
stats scope { <name> | "." }
Enable statistics and limit access scope
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 :
# public access (limited to this backend only)
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
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "stats auth", "stats enable", "stats realm", "stats uri"
stats uri <prefix>
Enable statistics and define the URI prefix to access them
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 explictly 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 :
# public access (limited to this backend only)
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
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "stats auth", "stats enable", "stats realm"
stats hide-version
Enable statistics and hide HAProxy version reporting
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
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 :
# public access (limited to this backend only)
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
# internal monitoring access (unlimited)
backend private_monitoring
stats enable
stats uri /admin?stats
stats refresh 5s
See also : "stats auth", "stats enable", "stats realm", "stats uri"
tcp-request content accept [{if | unless} <condition>]
Accept a connection if/unless a content inspection condition is matched
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | no
During TCP content inspection, the connection is immediately validated if the
condition is true (when used with "if") or false (when used with "unless").
Most of the time during content inspection, a condition will be in an
uncertain state which is neither true nor false. The evaluation immediately
stops when such a condition is encountered. It is important to understand
that "accept" and "reject" rules are evaluated in their exact declaration
order, so that it is possible to build complex rules from them. There is no
specific limit to the number of rules which may be inserted.
Note that the "if/unless" condition is optionnal. If no condition is set on
the action, it is simply performed unconditionally.
If no "tcp-request content" rules are matched, the default action already is
"accept". Thus, this statement alone does not bring anything without another
"reject" statement.
See section 7 about ACL usage.
See also : "tcp-request content reject", "tcp-request inspect-delay"
tcp-request content reject [{if | unless} <condition>]
Reject a connection if/unless a content inspection condition is matched
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | no
During TCP content inspection, the connection is immediately rejected if the
condition is true (when used with "if") or false (when used with "unless").
Most of the time during content inspection, a condition will be in an
uncertain state which is neither true nor false. The evaluation immediately
stops when such a condition is encountered. It is important to understand
that "accept" and "reject" rules are evaluated in their exact declaration
order, so that it is possible to build complex rules from them. There is no
specific limit to the number of rules which may be inserted.
Note that the "if/unless" condition is optionnal. If no condition is set on
the action, it is simply performed unconditionally.
If no "tcp-request content" rules are matched, the default action is set to
"accept".
Example:
# reject SMTP connection if client speaks first
tcp-request inspect-delay 30s
acl content_present req_len gt 0
tcp-request reject if content_present
# Forward HTTPS connection only if client speaks
tcp-request inspect-delay 30s
acl content_present req_len gt 0
tcp-request accept if content_present
tcp-request reject
See section 7 about ACL usage.
See also : "tcp-request content accept", "tcp-request inspect-delay"
tcp-request inspect-delay <timeout>
Set the maximum allowed time to wait for data during content inspection
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | no
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.
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 aforementionned 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.
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