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----------------------
HAProxy
Configuration Manual
----------------------
version 2.1
willy tarreau
2019/11/25
This document covers the configuration language as implemented in the version
specified above. It does not provide any hints, examples, or advice. For such
documentation, please refer to the Reference Manual or the Architecture Manual.
The summary below is meant to help you find sections by name and navigate
through the document.
Note to documentation contributors :
This document is formatted 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, indented by two characters. It is also
sometimes useful to prefix all output lines (logs, console outputs) with 3
closing angle brackets ('>>>') in order to emphasize the difference between
inputs and outputs when they may be ambiguous. 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. Quoting and escaping
2.3. Environment variables
2.4. Time format
2.5. Examples
3. Global parameters
3.1. Process management and security
3.2. Performance tuning
3.3. Debugging
3.4. Userlists
3.5. Peers
3.6. Mailers
3.7. Programs
4. Proxies
4.1. Proxy keywords matrix
4.2. Alphabetically sorted keywords reference
5. Bind and server options
5.1. Bind options
5.2. Server and default-server options
5.3. Server DNS resolution
5.3.1. Global overview
5.3.2. The resolvers section
7. Using ACLs and fetching samples
7.1. ACL basics
7.1.1. Matching booleans
7.1.2. Matching integers
7.1.3. Matching strings
7.1.4. Matching regular expressions (regexes)
7.1.5. Matching arbitrary data blocks
7.1.6. Matching IPv4 and IPv6 addresses
7.2. Using ACLs to form conditions
7.3. Fetching samples
7.3.1. Converters
7.3.2. Fetching samples from internal states
7.3.3. Fetching samples at Layer 4
7.3.4. Fetching samples at Layer 5
7.3.5. Fetching samples from buffer contents (Layer 6)
7.3.6. Fetching HTTP samples (Layer 7)
7.4. Pre-defined ACLs
6. Cache
6.1. Limitation
6.2. Setup
6.2.1. Cache section
6.2.2. Proxy section
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
8.2.4. Custom log format
8.2.5. Error 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. Supported filters
9.1. Trace
9.2. HTTP compression
9.3. Stream Processing Offload Engine (SPOE)
9.4. Cache
9.5. fcgi-app
10. FastCGI applications
10.1. Setup
10.1.1. Fcgi-app section
10.1.2. Proxy section
10.1.3. Example
10.2. Default parameters
10.3. Limitations
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. Traditionally, a TCP connection is established
from the client to the server, a request is sent by the client through 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.
Another 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.
The next improvement is the multiplexed mode, as implemented in HTTP/2. This
time, each transaction is assigned a single stream identifier, and all streams
are multiplexed over an existing connection. Many requests can be sent in
parallel by the client, and responses can arrive in any order since they also
carry the stream identifier.
By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and
leaves the connection idle on both sides between the end of a response and the
start of a new request. When it receives HTTP/2 connections from a client, it
processes all the requests in parallel and leaves the connection idling,
waiting for new requests, just as if it was a keep-alive HTTP connection.
HAProxy supports 4 connection modes :
- keep alive : all requests and responses are processed (default)
- tunnel : only the first request and response are processed,
everything else is forwarded with no analysis (deprecated).
- server close : the server-facing connection is closed after the response.
- close : the connection is actively closed after end of response.
For HTTP/2, the connection mode resembles more the "server close" mode : given
the independence of all streams, there is currently no place to hook the idle
server connection after a response, so it is closed after the response. HTTP/2
is only supported for incoming connections, not on connections going to
servers.
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.
HTTP/2 doesn't convey a version information with the request, so the version is
assumed to be the same as the one of the underlying protocol (i.e. "HTTP/2").
However, haproxy natively processes HTTP/1.x requests and headers, so requests
received over an HTTP/2 connection are transcoded to HTTP/1.1 before being
processed. This explains why they still appear as "HTTP/1.1" in haproxy's logs
as well as in server logs.
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 misconception, header names are not case-sensitive, and
their values are not either if they refer to other header names (such as the
"Connection:" header). In HTTP/2, header names are always sent in lower case,
as can be seen when running in debug mode.
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 RFC7231, 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
As a special case, HTTP supports so called "Informational responses" as status
codes 1xx. These messages are special in that they don't convey any part of the
response, they're just used as sort of a signaling message to ask a client to
continue to post its request for instance. In the case of a status 100 response
the requested information will be carried by the next non-100 response message
following the informational one. This implies that multiple responses may be
sent to a single request, and that this only works when keep-alive is enabled
(1xx messages are HTTP/1.1 only). HAProxy handles these messages and is able to
correctly forward and skip them, and only process the next non-100 response. As
such, these messages are neither logged nor transformed, unless explicitly
state otherwise. Status 101 messages indicate that the protocol is changing
over the same connection and that haproxy must switch to tunnel mode, just as
if a CONNECT had occurred. Then the Upgrade header would contain additional
information about the type of protocol the connection is switching to.
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 :
- 1xx = informational message to be skipped (e.g. 100, 101)
- 2xx = OK, content is following (e.g. 200, 206)
- 3xx = OK, no content following (e.g. 302, 304)
- 4xx = error caused by the client (e.g. 401, 403, 404)
- 5xx = error caused by the server (e.g. 500, 502, 503)
Please refer to RFC7231 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
307 when performing a redirection, depending on the configured code
308 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 "http-request deny" rule
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 "http-response deny" rule 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.
2.2. Quoting and escaping
-------------------------
HAProxy's configuration introduces a quoting and escaping system similar to
many programming languages. The configuration file supports 3 types: escaping
with a backslash, weak quoting with double quotes, and strong quoting with
single quotes.
If spaces have to be entered in strings, then they must be escaped by preceding
them by a backslash ('\') or by quoting them. Backslashes also have to be
escaped by doubling or strong quoting them.
Escaping is achieved by preceding a special character by a backslash ('\'):
\ to mark a space and differentiate it from a delimiter
\# to mark a hash and differentiate it from a comment
\\ to use a backslash
\' to use a single quote and differentiate it from strong quoting
\" to use a double quote and differentiate it from weak quoting
Weak quoting is achieved by using double quotes (""). Weak quoting prevents
the interpretation of:
space as a parameter separator
' single quote as a strong quoting delimiter
# hash as a comment start
Weak quoting permits the interpretation of variables, if you want to use a non
-interpreted dollar within a double quoted string, you should escape it with a
backslash ("\$"), it does not work outside weak quoting.
Interpretation of escaping and special characters are not prevented by weak
quoting.
Strong quoting is achieved by using single quotes (''). Inside single quotes,
nothing is interpreted, it's the efficient way to quote regexes.
Quoted and escaped strings are replaced in memory by their interpreted
equivalent, it allows you to perform concatenation.
Example:
# those are equivalents:
log-format %{+Q}o\ %t\ %s\ %{-Q}r
log-format "%{+Q}o %t %s %{-Q}r"
log-format '%{+Q}o %t %s %{-Q}r'
log-format "%{+Q}o %t"' %s %{-Q}r'
log-format "%{+Q}o %t"' %s'\ %{-Q}r
# those are equivalents:
reqrep "^([^\ :]*)\ /static/(.*)" \1\ /\2
reqrep "^([^ :]*)\ /static/(.*)" '\1 /\2'
reqrep "^([^ :]*)\ /static/(.*)" "\1 /\2"
reqrep "^([^ :]*)\ /static/(.*)" "\1\ /\2"
2.3. Environment variables
--------------------------
HAProxy's configuration supports environment variables. Those variables are
interpreted only within double quotes. Variables are expanded during the
configuration parsing. Variable names must be preceded by a dollar ("$") and
optionally enclosed with braces ("{}") similarly to what is done in Bourne
shell. Variable names can contain alphanumerical characters or the character
underscore ("_") but should not start with a digit.
Example:
bind "fd@${FD_APP1}"
log "${LOCAL_SYSLOG}:514" local0 notice # send to local server
user "$HAPROXY_USER"
Some variables are defined by HAProxy, they can be used in the configuration
file, or could be inherited by a program (See 3.7. Programs):
* HAPROXY_LOCALPEER: defined at the startup of the process which contains the
name of the local peer. (See "-L" in the management guide.)
* HAPROXY_CFGFILES: list of the configuration files loaded by HAProxy,
separated by semicolons. Can be useful in the case you specified a
directory.
* HAPROXY_MWORKER: In master-worker mode, this variable is set to 1.
* HAPROXY_CLI: configured listeners addresses of the stats socket for every
processes, separated by semicolons.
* HAPROXY_MASTER_CLI: In master-worker mode, listeners addresses of the master
CLI, separated by semicolons.
See also "external-check command" for other variables.
2.4. Time format
----------------
Some parameters involve values representing 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
2.5. Examples
-------------
# Simple configuration for an HTTP proxy listening on port 80 on all
# interfaces and forwarding requests to a single backend "servers" with a
# single server "server1" listening on 127.0.0.1:8000
global
daemon
maxconn 256
defaults
mode http
timeout connect 5000ms
timeout client 50000ms
timeout server 50000ms
frontend http-in
bind *:80
default_backend servers
backend servers
server server1 127.0.0.1:8000 maxconn 32
# The same configuration defined with a single listen block. Shorter but
# less expressive, especially in HTTP mode.
global
daemon
maxconn 256
defaults
mode http
timeout connect 5000ms
timeout client 50000ms
timeout server 50000ms
listen http-in
bind *:80
server server1 127.0.0.1:8000 maxconn 32
Assuming haproxy is in $PATH, test these configurations in a shell with:
$ sudo haproxy -f configuration.conf -c
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
- ca-base
- chroot
- crt-base
- cpu-map
- daemon
- description
- deviceatlas-json-file
- deviceatlas-log-level
- deviceatlas-separator
- deviceatlas-properties-cookie
- external-check
- gid
- group
- hard-stop-after
- h1-case-adjust
- h1-case-adjust-file
- log
- log-tag
- log-send-hostname
- lua-load
- mworker-max-reloads
- nbproc
- nbthread
- node
- pidfile
- presetenv
- resetenv
- uid
- ulimit-n
- user
- set-dumpable
- setenv
- stats
- ssl-default-bind-ciphers
- ssl-default-bind-ciphersuites
- ssl-default-bind-options
- ssl-default-server-ciphers
- ssl-default-server-ciphersuites
- ssl-default-server-options
- ssl-dh-param-file
- ssl-server-verify
- unix-bind
- unsetenv
- 51degrees-data-file
- 51degrees-property-name-list
- 51degrees-property-separator
- 51degrees-cache-size
- wurfl-data-file
- wurfl-information-list
- wurfl-information-list-separator
- wurfl-cache-size
- strict-limits
* Performance tuning
- busy-polling
- max-spread-checks
- maxconn
- maxconnrate
- maxcomprate
- maxcompcpuusage
- maxpipes
- maxsessrate
- maxsslconn
- maxsslrate
- maxzlibmem
- noepoll
- nokqueue
- noevports
- nopoll
- nosplice
- nogetaddrinfo
- noreuseport
- profiling.tasks
- spread-checks
- server-state-base
- server-state-file
- ssl-engine
- ssl-mode-async
- tune.buffers.limit
- tune.buffers.reserve
- tune.bufsize
- tune.chksize
- tune.comp.maxlevel
- tune.h2.header-table-size
- tune.h2.initial-window-size
- tune.h2.max-concurrent-streams
- tune.http.cookielen
- tune.http.logurilen
- tune.http.maxhdr
- tune.idletimer
- tune.lua.forced-yield
- tune.lua.maxmem
- tune.lua.session-timeout
- tune.lua.task-timeout
- tune.lua.service-timeout
- tune.maxaccept
- tune.maxpollevents
- tune.maxrewrite
- tune.pattern.cache-size
- tune.pipesize
- tune.rcvbuf.client
- tune.rcvbuf.server
- tune.recv_enough
- tune.runqueue-depth
- tune.sndbuf.client
- tune.sndbuf.server
- tune.ssl.cachesize
- tune.ssl.lifetime
- tune.ssl.force-private-cache
- tune.ssl.maxrecord
- tune.ssl.default-dh-param
- tune.ssl.ssl-ctx-cache-size
- tune.ssl.capture-cipherlist-size
- tune.vars.global-max-size
- tune.vars.proc-max-size
- tune.vars.reqres-max-size
- tune.vars.sess-max-size
- tune.vars.txn-max-size
- tune.zlib.memlevel
- tune.zlib.windowsize
* Debugging
- debug
- quiet
3.1. Process management and security
------------------------------------
ca-base <dir>
Assigns a default directory to fetch SSL CA certificates and CRLs from when a
relative path is used with "ca-file" or "crl-file" directives. Absolute
locations specified in "ca-file" and "crl-file" prevail and ignore "ca-base".
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 non-writable to anyone.
cpu-map [auto:]<process-set>[/<thread-set>] <cpu-set>...
On Linux 2.6 and above, it is possible to bind a process or a thread to a
specific CPU set. This means that the process or the thread will never run on
other CPUs. The "cpu-map" directive specifies CPU sets for process or thread
sets. The first argument is a process set, eventually followed by a thread
set. These sets have the format
all | odd | even | number[-[number]]
<number>> must be a number between 1 and 32 or 64, depending on the machine's
word size. Any process IDs above nbproc and any thread IDs above nbthread are
ignored. It is possible to specify a range with two such number delimited by
a dash ('-'). It also is possible to specify all processes at once using
"all", only odd numbers using "odd" or even numbers using "even", just like
with the "bind-process" directive. The second and forthcoming arguments are
CPU sets. Each CPU set is either a unique number between 0 and 31 or 63 or a
range with two such numbers delimited by a dash ('-'). Multiple CPU numbers
or ranges may be specified, and the processes or threads will be allowed to
bind to all of them. Obviously, multiple "cpu-map" directives may be
specified. Each "cpu-map" directive will replace the previous ones when they
overlap. A thread will be bound on the intersection of its mapping and the
one of the process on which it is attached. If the intersection is null, no
specific binding will be set for the thread.
Ranges can be partially defined. The higher bound can be omitted. In such
case, it is replaced by the corresponding maximum value, 32 or 64 depending
on the machine's word size.
The prefix "auto:" can be added before the process set to let HAProxy
automatically bind a process or a thread to a CPU by incrementing
process/thread and CPU sets. To be valid, both sets must have the same
size. No matter the declaration order of the CPU sets, it will be bound from
the lowest to the highest bound. Having a process and a thread range with the
"auto:" prefix is not supported. Only one range is supported, the other one
must be a fixed number.
Examples:
cpu-map 1-4 0-3 # bind processes 1 to 4 on the first 4 CPUs
cpu-map 1/all 0-3 # bind all threads of the first process on the
# first 4 CPUs
cpu-map 1- 0- # will be replaced by "cpu-map 1-64 0-63"
# or "cpu-map 1-32 0-31" depending on the machine's
# word size.
# all these lines bind the process 1 to the cpu 0, the process 2 to cpu 1
# and so on.
cpu-map auto:1-4 0-3
cpu-map auto:1-4 0-1 2-3
cpu-map auto:1-4 3 2 1 0
# all these lines bind the thread 1 to the cpu 0, the thread 2 to cpu 1
# and so on.
cpu-map auto:1/1-4 0-3
cpu-map auto:1/1-4 0-1 2-3
cpu-map auto:1/1-4 3 2 1 0
# bind each process to exactly one CPU using all/odd/even keyword
cpu-map auto:all 0-63
cpu-map auto:even 0-31
cpu-map auto:odd 32-63
# invalid cpu-map because process and CPU sets have different sizes.
cpu-map auto:1-4 0 # invalid
cpu-map auto:1 0-3 # invalid
# invalid cpu-map because automatic binding is used with a process range
# and a thread range.
cpu-map auto:all/all 0 # invalid
cpu-map auto:all/1-4 0 # invalid
cpu-map auto:1-4/all 0 # invalid
crt-base <dir>
Assigns a default directory to fetch SSL certificates from when a relative
path is used with "crtfile" directives. Absolute locations specified after
"crtfile" prevail and ignore "crt-base".
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. This option is ignored in
systemd mode.
deviceatlas-json-file <path>
Sets the path of the DeviceAtlas JSON data file to be loaded by the API.
The path must be a valid JSON data file and accessible by HAProxy process.
deviceatlas-log-level <value>
Sets the level of information returned by the API. This directive is
optional and set to 0 by default if not set.
deviceatlas-separator <char>
Sets the character separator for the API properties results. This directive
is optional and set to | by default if not set.
deviceatlas-properties-cookie <name>
Sets the client cookie's name used for the detection if the DeviceAtlas
Client-side component was used during the request. This directive is optional
and set to DAPROPS by default if not set.
external-check
Allows the use of an external agent to perform health checks.
This is disabled by default as a security precaution.
See "option external-check".
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.
Note that if haproxy is started from a user having supplementary groups, it
will only be able to drop these groups if started with superuser privileges.
See also "group" and "uid".
hard-stop-after <time>
Defines the maximum time allowed to perform a clean soft-stop.
Arguments :
<time> is the maximum time (by default in milliseconds) for which the
instance will remain alive when a soft-stop is received via the
SIGUSR1 signal.
This may be used to ensure that the instance will quit even if connections
remain opened during a soft-stop (for example with long timeouts for a proxy
in tcp mode). It applies both in TCP and HTTP mode.
Example:
global
hard-stop-after 30s
h1-case-adjust <from> <to>
Defines the case adjustment to apply, when enabled, to the header name
<from>, to change it to <to> before sending it to HTTP/1 clients or
servers. <from> must be in lower case, and <from> and <to> must not differ
except for their case. It may be repeated if several header names need to be
ajusted. Duplicate entries are not allowed. If a lot of header names have to
be adjusted, it might be more convenient to use "h1-case-adjust-file".
Please note that no transformation will be applied unless "option
h1-case-adjust-bogus-client" or "option h1-case-adjust-bogus-server" is
specified in a proxy.
There is no standard case for header names because, as stated in RFC7230,
they are case-insensitive. So applications must handle them in a case-
insensitive manner. But some bogus applications violate the standards and
erroneously rely on the cases most commonly used by browsers. This problem
becomes critical with HTTP/2 because all header names must be exchanged in
lower case, and HAProxy follows the same convention. All header names are
sent in lower case to clients and servers, regardless of the HTTP version.
Applications which fail to properly process requests or responses may require
to temporarily use such workarounds to adjust header names sent to them for
the time it takes the application to be fixed. Please note that an
application which requires such workarounds might be vulnerable to content
smuggling attacks and must absolutely be fixed.
Example:
global
h1-case-adjust content-length Content-Length
See "h1-case-adjust-file", "option h1-case-adjust-bogus-client" and
"option h1-case-adjust-bogus-server".
h1-case-adjust-file <hdrs-file>
Defines a file containing a list of key/value pairs used to adjust the case
of some header names before sending them to HTTP/1 clients or servers. The
file <hdrs-file> must contain 2 header names per line. The first one must be
in lower case and both must not differ except for their case. Lines which
start with '#' are ignored, just like empty lines. Leading and trailing tabs
and spaces are stripped. Duplicate entries are not allowed. Please note that
no transformation will be applied unless "option h1-case-adjust-bogus-client"
or "option h1-case-adjust-bogus-server" is specified in a proxy.
If this directive is repeated, only the last one will be processed. It is an
alternative to the directive "h1-case-adjust" if a lot of header names need
to be adjusted. Please read the risks associated with using this.
See "h1-case-adjust", "option h1-case-adjust-bogus-client" and
"option h1-case-adjust-bogus-server".
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> [len <length>] [format <format>] [sample <ranges>:<smp_size>]
<facility> [max level [min level]]
Adds a global syslog server. Several global servers can be defined. They
will receive logs for starts 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).
- An IPv6 address followed by a colon and optionally a UDP port. If
no port is specified, 514 is used by default (the standard syslog
port).
- A filesystem path to a datagram UNIX domain socket, keeping in mind
considerations for chroot (be sure the path is accessible inside
the chroot) and uid/gid (be sure the path is appropriately
writable).
- A file descriptor number in the form "fd@<number>", which may point
to a pipe, terminal, or socket. In this case unbuffered logs are used
and one writev() call per log is performed. This is a bit expensive
but acceptable for most workloads. Messages sent this way will not be
truncated but may be dropped, in which case the DroppedLogs counter
will be incremented. The writev() call is atomic even on pipes for
messages up to PIPE_BUF size, which POSIX recommends to be at least
512 and which is 4096 bytes on most modern operating systems. Any
larger message may be interleaved with messages from other processes.
Exceptionally for debugging purposes the file descriptor may also be
directed to a file, but doing so will significantly slow haproxy down
as non-blocking calls will be ignored. Also there will be no way to
purge nor rotate this file without restarting the process. Note that
the configured syslog format is preserved, so the output is suitable
for use with a TCP syslog server. See also the "short" and "raw"
format below.
- "stdout" / "stderr", which are respectively aliases for "fd@1" and
"fd@2", see above.
- A ring buffer in the form "ring@<name>", which will correspond to an
in-memory ring buffer accessible over the CLI using the "show events"
command, which will also list existing rings and their sizes. Such
buffers are lost on reload or restart but when used as a complement
this can help troubleshooting by having the logs instantly available.
You may want to reference some environment variables in the address
parameter, see section 2.3 about environment variables.
<length> is an optional maximum line length. Log lines larger than this value
will be truncated before being sent. The reason is that syslog
servers act differently on log line length. All servers support the
default value of 1024, but some servers simply drop larger lines
while others do log them. If a server supports long lines, it may
make sense to set this value here in order to avoid truncating long
lines. Similarly, if a server drops long lines, it is preferable to
truncate them before sending them. Accepted values are 80 to 65535
inclusive. The default value of 1024 is generally fine for all
standard usages. Some specific cases of long captures or
JSON-formatted logs may require larger values. You may also need to
increase "tune.http.logurilen" if your request URIs are truncated.
<format> is the log format used when generating syslog messages. It may be
one of the following :
rfc3164 The RFC3164 syslog message format. This is the default.
(https://tools.ietf.org/html/rfc3164)
rfc5424 The RFC5424 syslog message format.
(https://tools.ietf.org/html/rfc5424)
short A message containing only a level between angle brackets such as
'<3>', followed by the text. The PID, date, time, process name
and system name are omitted. This is designed to be used with a
local log server. This format is compatible with what the systemd
logger consumes.
raw A message containing only the text. The level, PID, date, time,
process name and system name are omitted. This is designed to be
used in containers or during development, where the severity only
depends on the file descriptor used (stdout/stderr).
<ranges> A list of comma-separated ranges to identify the logs to sample.
This is used to balance the load of the logs to send to the log
server. The limits of the ranges cannot be null. They are numbered
from 1. The size or period (in number of logs) of the sample must be
set with <sample_size> parameter.
<sample_size>
The size of the sample in number of logs to consider when balancing
their logging loads. It is used to balance the load of the logs to
send to the syslog server. This size must be greater or equal to the
maximum of the high limits of the ranges.
(see also <ranges> parameter).
<facility> must be one of the 24 standard syslog facilities :
kern user mail daemon auth syslog lpr news
uucp cron auth2 ftp ntp audit alert cron2
local0 local1 local2 local3 local4 local5 local6 local7
Note that the facility is ignored for the "short" and "raw"
formats, but still required as a positional field. It is
recommended to use "daemon" in this case to make it clear that
it's only supposed to be used locally.
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
log-send-hostname [<string>]
Sets the hostname field in the syslog header. If optional "string" parameter
is set the header is set to the string contents, otherwise uses the hostname
of the system. Generally used if one is not relaying logs through an
intermediate syslog server or for simply customizing the hostname printed in
the logs.
log-tag <string>
Sets the tag field in the syslog header to this string. It defaults to the
program name as launched from the command line, which usually is "haproxy".
Sometimes it can be useful to differentiate between multiple processes
running on the same host. See also the per-proxy "log-tag" directive.
lua-load <file>
This global directive loads and executes a Lua file. This directive can be
used multiple times.
master-worker [no-exit-on-failure]
Master-worker mode. It is equivalent to the command line "-W" argument.
This mode will launch a "master" which will monitor the "workers". Using
this mode, you can reload HAProxy directly by sending a SIGUSR2 signal to
the master. The master-worker mode is compatible either with the foreground
or daemon mode. It is recommended to use this mode with multiprocess and
systemd.
By default, if a worker exits with a bad return code, in the case of a
segfault for example, all workers will be killed, and the master will leave.
It is convenient to combine this behavior with Restart=on-failure in a
systemd unit file in order to relaunch the whole process. If you don't want
this behavior, you must use the keyword "no-exit-on-failure".
See also "-W" in the management guide.
mworker-max-reloads <number>
In master-worker mode, this option limits the number of time a worker can
survive to a reload. If the worker did not leave after a reload, once its
number of reloads is greater than this number, the worker will receive a
SIGTERM. This option helps to keep under control the number of workers.
See also "show proc" in the Management Guide.
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. When set to a value
larger than 1, threads are automatically disabled. USING MULTIPLE PROCESSES
IS HARDER TO DEBUG AND IS REALLY DISCOURAGED. See also "daemon" and
"nbthread".
nbthread <number>
This setting is only available when support for threads was built in. It
makes haproxy run on <number> threads. This is exclusive with "nbproc". While
"nbproc" historically used to be the only way to use multiple processors, it
also involved a number of shortcomings related to the lack of synchronization
between processes (health-checks, peers, stick-tables, stats, ...) which do
not affect threads. As such, any modern configuration is strongly encouraged
to migrate away from "nbproc" to "nbthread". "nbthread" also works when
HAProxy is started in foreground. On some platforms supporting CPU affinity,
when nbproc is not used, the default "nbthread" value is automatically set to
the number of CPUs the process is bound to upon startup. This means that the
thread count can easily be adjusted from the calling process using commands
like "taskset" or "cpuset". Otherwise, this value defaults to 1. The default
value is reported in the output of "haproxy -vv". See also "nbproc".
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".
presetenv <name> <value>
Sets environment variable <name> to value <value>. If the variable exists, it
is NOT overwritten. The changes immediately take effect so that the next line
in the configuration file sees the new value. See also "setenv", "resetenv",
and "unsetenv".
resetenv [<name> ...]
Removes all environment variables except the ones specified in argument. It
allows to use a clean controlled environment before setting new values with
setenv or unsetenv. Please note that some internal functions may make use of
some environment variables, such as time manipulation functions, but also
OpenSSL or even external checks. This must be used with extreme care and only
after complete validation. The changes immediately take effect so that the
next line in the configuration file sees the new environment. See also
"setenv", "presetenv", and "unsetenv".
stats bind-process [ all | odd | even | <process_num>[-[process_num>]] ] ...
Limits the stats socket to a certain set of processes numbers. By default the
stats socket is bound to all processes, causing a warning to be emitted when
nbproc is greater than 1 because there is no way to select the target process
when connecting. However, by using this setting, it becomes possible to pin
the stats socket to a specific set of processes, typically the first one. The
warning will automatically be disabled when this setting is used, whatever
the number of processes used. The maximum process ID depends on the machine's
word size (32 or 64). Ranges can be partially defined. The higher bound can
be omitted. In such case, it is replaced by the corresponding maximum
value. A better option consists in using the "process" setting of the "stats
socket" line to force the process on each line.
server-state-base <directory>
Specifies the directory prefix to be prepended in front of all servers state
file names which do not start with a '/'. See also "server-state-file",
"load-server-state-from-file" and "server-state-file-name".
server-state-file <file>
Specifies the path to the file containing state of servers. If the path starts
with a slash ('/'), it is considered absolute, otherwise it is considered
relative to the directory specified using "server-state-base" (if set) or to
the current directory. Before reloading HAProxy, it is possible to save the
servers' current state using the stats command "show servers state". The
output of this command must be written in the file pointed by <file>. When
starting up, before handling traffic, HAProxy will read, load and apply state
for each server found in the file and available in its current running
configuration. See also "server-state-base" and "show servers state",
"load-server-state-from-file" and "server-state-file-name"
setenv <name> <value>
Sets environment variable <name> to value <value>. If the variable exists, it
is overwritten. The changes immediately take effect so that the next line in
the configuration file sees the new value. See also "presetenv", "resetenv",
and "unsetenv".
set-dumpable
This option is better left disabled by default and enabled only upon a
developer's request. If it has been enabled, it may still be forcibly
disabled by prefixing it with the "no" keyword. It has no impact on
performance nor stability but will try hard to re-enable core dumps that were
possibly disabled by file size limitations (ulimit -f), core size limitations
(ulimit -c), or "dumpability" of a process after changing its UID/GID (such
as /proc/sys/fs/suid_dumpable on Linux). Core dumps might still be limited by
the current directory's permissions (check what directory the file is started
from), the chroot directory's permission (it may be needed to temporarily
disable the chroot directive or to move it to a dedicated writable location),
or any other system-specific constraint. For example, some Linux flavours are
notorious for replacing the default core file with a path to an executable
not even installed on the system (check /proc/sys/kernel/core_pattern). Often,
simply writing "core", "core.%p" or "/var/log/core/core.%p" addresses the
issue. When trying to enable this option waiting for a rare issue to
re-appear, it's often a good idea to first try to obtain such a dump by
issuing, for example, "kill -11" to the haproxy process and verify that it
leaves a core where expected when dying.
ssl-default-bind-ciphers <ciphers>
This setting is only available when support for OpenSSL was built in. It sets
the default string describing the list of cipher algorithms ("cipher suite")
that are negotiated during the SSL/TLS handshake up to TLSv1.2 for all
"bind" lines which do not explicitly define theirs. The format of the string
is defined in "man 1 ciphers" from OpenSSL man pages. For background
information and recommendations see e.g.
(https://wiki.mozilla.org/Security/Server_Side_TLS) and
(https://mozilla.github.io/server-side-tls/ssl-config-generator/). For TLSv1.3
cipher configuration, please check the "ssl-default-bind-ciphersuites" keyword.
Please check the "bind" keyword for more information.
ssl-default-bind-ciphersuites <ciphersuites>
This setting is only available when support for OpenSSL was built in and
OpenSSL 1.1.1 or later was used to build HAProxy. It sets the default string
describing the list of cipher algorithms ("cipher suite") that are negotiated
during the TLSv1.3 handshake for all "bind" lines which do not explicitly define
theirs. The format of the string is defined in
"man 1 ciphers" from OpenSSL man pages under the section "ciphersuites". For
cipher configuration for TLSv1.2 and earlier, please check the
"ssl-default-bind-ciphers" keyword. Please check the "bind" keyword for more
information.
ssl-default-bind-options [<option>]...
This setting is only available when support for OpenSSL was built in. It sets
default ssl-options to force on all "bind" lines. Please check the "bind"
keyword to see available options.
Example:
global
ssl-default-bind-options ssl-min-ver TLSv1.0 no-tls-tickets
ssl-default-server-ciphers <ciphers>
This setting is only available when support for OpenSSL was built in. It
sets the default string describing the list of cipher algorithms that are
negotiated during the SSL/TLS handshake up to TLSv1.2 with the server,
for all "server" lines which do not explicitly define theirs. The format of
the string is defined in "man 1 ciphers" from OpenSSL man pages. For background
information and recommendations see e.g.
(https://wiki.mozilla.org/Security/Server_Side_TLS) and
(https://mozilla.github.io/server-side-tls/ssl-config-generator/).
For TLSv1.3 cipher configuration, please check the
"ssl-default-server-ciphersuites" keyword. Please check the "server" keyword
for more information.
ssl-default-server-ciphersuites <ciphersuites>
This setting is only available when support for OpenSSL was built in and
OpenSSL 1.1.1 or later was used to build HAProxy. It sets the default
string describing the list of cipher algorithms that are negotiated during
the TLSv1.3 handshake with the server, for all "server" lines which do not
explicitly define theirs. The format of the string is defined in
"man 1 ciphers" from OpenSSL man pages under the section "ciphersuites". For
cipher configuration for TLSv1.2 and earlier, please check the
"ssl-default-server-ciphers" keyword. Please check the "server" keyword for
more information.
ssl-default-server-options [<option>]...
This setting is only available when support for OpenSSL was built in. It sets
default ssl-options to force on all "server" lines. Please check the "server"
keyword to see available options.
ssl-dh-param-file <file>
This setting is only available when support for OpenSSL was built in. It sets
the default DH parameters that are used during the SSL/TLS handshake when
ephemeral Diffie-Hellman (DHE) key exchange is used, for all "bind" lines
which do not explicitly define theirs. It will be overridden by custom DH
parameters found in a bind certificate file if any. If custom DH parameters
are not specified either by using ssl-dh-param-file or by setting them
directly in the certificate file, pre-generated DH parameters of the size
specified by tune.ssl.default-dh-param will be used. Custom parameters are
known to be more secure and therefore their use is recommended.
Custom DH parameters may be generated by using the OpenSSL command
"openssl dhparam <size>", where size should be at least 2048, as 1024-bit DH
parameters should not be considered secure anymore.
ssl-server-verify [none|required]
The default behavior for SSL verify on servers side. If specified to 'none',
servers certificates are not verified. The default is 'required' except if
forced using cmdline option '-dV'.
stats socket [<address:port>|<path>] [param*]
Binds a UNIX socket to <path> or a TCPv4/v6 address to <address:port>.
Connections to this socket will return various statistics outputs and even
allow some commands to be issued to change some runtime settings. Please
consult section 9.3 "Unix Socket commands" of Management Guide for more
details.
All parameters supported by "bind" lines are supported, for instance to
restrict access to some users or their access rights. Please consult
section 5.1 for more information.
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.
unix-bind [ prefix <prefix> ] [ mode <mode> ] [ user <user> ] [ uid <uid> ]
[ group <group> ] [ gid <gid> ]
Fixes common settings to UNIX listening sockets declared in "bind" statements.
This is mainly used to simplify declaration of those UNIX sockets and reduce
the risk of errors, since those settings are most commonly required but are
also process-specific. The <prefix> setting can be used to force all socket
path to be relative to that directory. This might be needed to access another
component's chroot. Note that those paths are resolved before haproxy chroots
itself, so they are absolute. The <mode>, <user>, <uid>, <group> and <gid>
all have the same meaning as their homonyms used by the "bind" statement. If
both are specified, the "bind" statement has priority, meaning that the
"unix-bind" settings may be seen as process-wide default settings.
unsetenv [<name> ...]
Removes environment variables specified in arguments. This can be useful to
hide some sensitive information that are occasionally inherited from the
user's environment during some operations. Variables which did not exist are
silently ignored so that after the operation, it is certain that none of
these variables remain. The changes immediately take effect so that the next
line in the configuration file will not see these variables. See also
"setenv", "presetenv", and "resetenv".
user <user name>
Similar to "uid" but uses the UID of user name <user name> from /etc/passwd.
See also "uid" and "group".
node <name>
Only letters, digits, hyphen and underscore are allowed, like in DNS names.
This statement is useful in HA configurations where two or more processes or
servers share the same IP address. By setting a different node-name on all
nodes, it becomes easy to immediately spot what server is handling the
traffic.
description <text>
Add a text that describes the instance.
Please note that it is required to escape certain characters (# for example)
and this text is inserted into a html page so you should avoid using
"<" and ">" characters.
51degrees-data-file <file path>
The path of the 51Degrees data file to provide device detection services. The
file should be unzipped and accessible by HAProxy with relevant permissions.
Please note that this option is only available when haproxy has been
compiled with USE_51DEGREES.
51degrees-property-name-list [<string> ...]
A list of 51Degrees property names to be load from the dataset. A full list
of names is available on the 51Degrees website:
https://51degrees.com/resources/property-dictionary
Please note that this option is only available when haproxy has been
compiled with USE_51DEGREES.
51degrees-property-separator <char>
A char that will be appended to every property value in a response header
containing 51Degrees results. If not set that will be set as ','.
Please note that this option is only available when haproxy has been
compiled with USE_51DEGREES.
51degrees-cache-size <number>
Sets the size of the 51Degrees converter cache to <number> entries. This
is an LRU cache which reminds previous device detections and their results.
By default, this cache is disabled.
Please note that this option is only available when haproxy has been
compiled with USE_51DEGREES.
wurfl-data-file <file path>
The path of the WURFL data file to provide device detection services. The
file should be accessible by HAProxy with relevant permissions.
Please note that this option is only available when haproxy has been compiled
with USE_WURFL=1.
wurfl-information-list [<capability>]*
A space-delimited list of WURFL capabilities, virtual capabilities, property
names we plan to use in injected headers. A full list of capability and
virtual capability names is available on the Scientiamobile website :
https://www.scientiamobile.com/wurflCapability
Valid WURFL properties are:
- wurfl_id Contains the device ID of the matched device.
- wurfl_root_id Contains the device root ID of the matched
device.
- wurfl_isdevroot Tells if the matched device is a root device.
Possible values are "TRUE" or "FALSE".
- wurfl_useragent The original useragent coming with this
particular web request.
- wurfl_api_version Contains a string representing the currently
used Libwurfl API version.
- wurfl_info A string containing information on the parsed
wurfl.xml and its full path.
- wurfl_last_load_time Contains the UNIX timestamp of the last time
WURFL has been loaded successfully.
- wurfl_normalized_useragent The normalized useragent.
Please note that this option is only available when haproxy has been compiled
with USE_WURFL=1.
wurfl-information-list-separator <char>
A char that will be used to separate values in a response header containing
WURFL results. If not set that a comma (',') will be used by default.
Please note that this option is only available when haproxy has been compiled
with USE_WURFL=1.
wurfl-patch-file [<file path>]
A list of WURFL patch file paths. Note that patches are loaded during startup
thus before the chroot.
Please note that this option is only available when haproxy has been compiled
with USE_WURFL=1.
wurfl-cache-size <size>
Sets the WURFL Useragent cache size. For faster lookups, already processed user
agents are kept in a LRU cache :
- "0" : no cache is used.
- <size> : size of lru cache in elements.
Please note that this option is only available when haproxy has been compiled
with USE_WURFL=1.
strict-limits
Makes process fail at startup when a setrlimit fails. Haproxy is tries to set
the best setrlimit according to what has been calculated. If it fails, it
will emit a warning. Use this option if you want an explicit failure of
haproxy when those limits fail. This option is disabled by default. If it has
been enabled, it may still be forcibly disabled by prefixing it with the "no"
keyword.
3.2. Performance tuning
-----------------------
busy-polling
In some situations, especially when dealing with low latency on processors
supporting a variable frequency or when running inside virtual machines, each
time the process waits for an I/O using the poller, the processor goes back
to sleep or is offered to another VM for a long time, and it causes
excessively high latencies. This option provides a solution preventing the
processor from sleeping by always using a null timeout on the pollers. This
results in a significant latency reduction (30 to 100 microseconds observed)
at the expense of a risk to overheat the processor. It may even be used with
threads, in which case improperly bound threads may heavily conflict,
resulting in a worse performance and high values for the CPU stolen fields
in "show info" output, indicating which threads are misconfigured. It is
important not to let the process run on the same processor as the network
interrupts when this option is used. It is also better to avoid using it on
multiple CPU threads sharing the same core. This option is disabled by
default. If it has been enabled, it may still be forcibly disabled by
prefixing it with the "no" keyword. It is ignored by the "select" and
"poll" pollers.
max-spread-checks <delay in milliseconds>
By default, haproxy tries to spread the start of health checks across the
smallest health check interval of all the servers in a farm. The principle is
to avoid hammering services running on the same server. But when using large
check intervals (10 seconds or more), the last servers in the farm take some
time before starting to be tested, which can be a problem. This parameter is
used to enforce an upper bound on delay between the first and the last check,
even if the servers' check intervals are larger. When servers run with
shorter intervals, their intervals will be respected though.
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". Note:
the "select" poller cannot reliably use more than 1024 file descriptors on
some platforms. If your platform only supports select and reports "select
FAILED" on startup, you need to reduce maxconn until it works (slightly
below 500 in general). If this value is not set, it will automatically be
calculated based on the current file descriptors limit reported by the
"ulimit -n" command, possibly reduced to a lower value if a memory limit
is enforced, based on the buffer size, memory allocated to compression, SSL
cache size, and use or not of SSL and the associated maxsslconn (which can
also be automatic).
maxconnrate <number>
Sets the maximum per-process number of connections per second to <number>.
Proxies will stop accepting connections when this limit is reached. It can be
used to limit the global capacity regardless of each frontend capacity. It is
important to note that this can only be used as a service protection measure,
as there will not necessarily be a fair share between frontends when the
limit is reached, so it's a good idea to also limit each frontend to some
value close to its expected share. Also, lowering tune.maxaccept can improve
fairness.
maxcomprate <number>
Sets the maximum per-process input compression rate to <number> kilobytes
per second. For each session, if the maximum is reached, the compression
level will be decreased during the session. If the maximum is reached at the
beginning of a session, the session will not compress at all. If the maximum
is not reached, the compression level will be increased up to
tune.comp.maxlevel. A value of zero means there is no limit, this is the
default value.
maxcompcpuusage <number>
Sets the maximum CPU usage HAProxy can reach before stopping the compression
for new requests or decreasing the compression level of current requests.
It works like 'maxcomprate' but measures CPU usage instead of incoming data
bandwidth. The value is expressed in percent of the CPU used by haproxy. In
case of multiple processes (nbproc > 1), each process manages its individual
usage. A value of 100 disable the limit. The default value is 100. Setting
a lower value will prevent the compression work from slowing the whole
process down and from introducing high latencies.
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.
maxsessrate <number>
Sets the maximum per-process number of sessions per second to <number>.
Proxies will stop accepting connections when this limit is reached. It can be
used to limit the global capacity regardless of each frontend capacity. It is
important to note that this can only be used as a service protection measure,
as there will not necessarily be a fair share between frontends when the
limit is reached, so it's a good idea to also limit each frontend to some
value close to its expected share. Also, lowering tune.maxaccept can improve
fairness.
maxsslconn <number>
Sets the maximum per-process number of concurrent SSL connections to
<number>. By default there is no SSL-specific limit, which means that the
global maxconn setting will apply to all connections. Setting this limit
avoids having openssl use too much memory and crash when malloc returns NULL
(since it unfortunately does not reliably check for such conditions). Note
that the limit applies both to incoming and outgoing connections, so one
connection which is deciphered then ciphered accounts for 2 SSL connections.
If this value is not set, but a memory limit is enforced, this value will be
automatically computed based on the memory limit, maxconn, the buffer size,
memory allocated to compression, SSL cache size, and use of SSL in either
frontends, backends or both. If neither maxconn nor maxsslconn are specified
when there is a memory limit, haproxy will automatically adjust these values
so that 100% of the connections can be made over SSL with no risk, and will
consider the sides where it is enabled (frontend, backend, both).
maxsslrate <number>
Sets the maximum per-process number of SSL sessions per second to <number>.
SSL listeners will stop accepting connections when this limit is reached. It
can be used to limit the global SSL CPU usage regardless of each frontend
capacity. It is important to note that this can only be used as a service
protection measure, as there will not necessarily be a fair share between
frontends when the limit is reached, so it's a good idea to also limit each
frontend to some value close to its expected share. It is also important to
note that the sessions are accounted before they enter the SSL stack and not
after, which also protects the stack against bad handshakes. Also, lowering
tune.maxaccept can improve fairness.
maxzlibmem <number>
Sets the maximum amount of RAM in megabytes per process usable by the zlib.
When the maximum amount is reached, future sessions will not compress as long
as RAM is unavailable. When sets to 0, there is no limit.
The default value is 0. The value is available in bytes on the UNIX socket
with "show info" on the line "MaxZlibMemUsage", the memory used by zlib is
"ZlibMemUsage" in bytes.
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 "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".
noevports
Disables the use of the event ports event polling system on SunOS systems
derived from Solaris 10 and later. It is equivalent to the command-line
argument "-dv". The next polling system used will generally be "poll". See
also "nopoll".
nopoll
Disables the use of the "poll" event polling system. It is equivalent to the
command-line argument "-dp". The next polling system used will be "select".
It should never be needed to disable "poll" since it's available on all
platforms supported by HAProxy. See also "nokqueue", "noepoll" and
"noevports".
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 versions between
2.6.25 and 2.6.28 are buggy and will forward corrupted data, so they must not
be used. This option makes it easier to globally disable kernel splicing in
case of doubt. See also "option splice-auto", "option splice-request" and
"option splice-response".
nogetaddrinfo
Disables the use of getaddrinfo(3) for name resolving. It is equivalent to
the command line argument "-dG". Deprecated gethostbyname(3) will be used.
noreuseport
Disables the use of SO_REUSEPORT - see socket(7). It is equivalent to the
command line argument "-dR".
profiling.tasks { auto | on | off }
Enables ('on') or disables ('off') per-task CPU profiling. When set to 'auto'
the profiling automatically turns on a thread when it starts to suffer from
an average latency of 1000 microseconds or higher as reported in the
"avg_loop_us" activity field, and automatically turns off when the latency
returns below 990 microseconds (this value is an average over the last 1024
loops so it does not vary quickly and tends to significantly smooth short
spikes). It may also spontaneously trigger from time to time on overloaded
systems, containers, or virtual machines, or when the system swaps (which
must absolutely never happen on a load balancer).
CPU profiling per task can be very convenient to report where the time is
spent and which requests have what effect on which other request. Enabling
it will typically affect the overall's performance by less than 1%, thus it
is recommended to leave it to the default 'auto' value so that it only
operates when a problem is identified. This feature requires a system
supporting the clock_gettime(2) syscall with clock identifiers
CLOCK_MONOTONIC and CLOCK_THREAD_CPUTIME_ID, otherwise the reported time will
be zero. This option may be changed at run time using "set profiling" on the
CLI.
spread-checks <0..50, in percent>
Sometimes it is desirable to avoid sending agent and health checks to
servers at exact intervals, for instance when many logical servers are
located on the same physical server. With the help of this parameter, it
becomes possible to add some randomness in the check interval between 0
and +/- 50%. A value between 2 and 5 seems to show good results. The
default value remains at 0.
ssl-engine <name> [algo <comma-separated list of algorithms>]
Sets the OpenSSL engine to <name>. List of valid values for <name> may be
obtained using the command "openssl engine". This statement may be used
multiple times, it will simply enable multiple crypto engines. Referencing an
unsupported engine will prevent haproxy from starting. Note that many engines
will lead to lower HTTPS performance than pure software with recent
processors. The optional command "algo" sets the default algorithms an ENGINE
will supply using the OPENSSL function ENGINE_set_default_string(). A value
of "ALL" uses the engine for all cryptographic operations. If no list of
algo is specified then the value of "ALL" is used. A comma-separated list
of different algorithms may be specified, including: RSA, DSA, DH, EC, RAND,
CIPHERS, DIGESTS, PKEY, PKEY_CRYPTO, PKEY_ASN1. This is the same format that
openssl configuration file uses:
https://www.openssl.org/docs/man1.0.2/apps/config.html
ssl-mode-async
Adds SSL_MODE_ASYNC mode to the SSL context. This enables asynchronous TLS
I/O operations if asynchronous capable SSL engines are used. The current
implementation supports a maximum of 32 engines. The Openssl ASYNC API
doesn't support moving read/write buffers and is not compliant with
haproxy's buffer management. So the asynchronous mode is disabled on
read/write operations (it is only enabled during initial and renegotiation
handshakes).
tune.buffers.limit <number>
Sets a hard limit on the number of buffers which may be allocated per process.
The default value is zero which means unlimited. The minimum non-zero value
will always be greater than "tune.buffers.reserve" and should ideally always
be about twice as large. Forcing this value can be particularly useful to
limit the amount of memory a process may take, while retaining a sane
behavior. When this limit is reached, sessions which need a buffer wait for
another one to be released by another session. Since buffers are dynamically
allocated and released, the waiting time is very short and not perceptible
provided that limits remain reasonable. In fact sometimes reducing the limit
may even increase performance by increasing the CPU cache's efficiency. Tests
have shown good results on average HTTP traffic with a limit to 1/10 of the
expected global maxconn setting, which also significantly reduces memory
usage. The memory savings come from the fact that a number of connections
will not allocate 2*tune.bufsize. It is best not to touch this value unless
advised to do so by an haproxy core developer.
tune.buffers.reserve <number>
Sets the number of buffers which are pre-allocated and reserved for use only
during memory shortage conditions resulting in failed memory allocations. The
minimum value is 2 and is also the default. There is no reason a user would
want to change this value, it's mostly aimed at haproxy core developers.
tune.bufsize <number>
Sets the buffer size to this size (in bytes). Lower values allow more
sessions to coexist in the same amount of RAM, and higher values allow some
applications with very large cookies to work. The default value is 16384 and
can be changed at build time. It is strongly recommended not to change this
from the default value, as very low values will break some services such as
statistics, and values larger than default size will increase memory usage,
possibly causing the system to run out of memory. At least the global maxconn
parameter should be decreased by the same factor as this one is increased. In
addition, use of HTTP/2 mandates that this value must be 16384 or more. If an
HTTP request is larger than (tune.bufsize - tune.maxrewrite), haproxy will
return HTTP 400 (Bad Request) error. Similarly if an HTTP response is larger
than this size, haproxy will return HTTP 502 (Bad Gateway). Note that the
value set using this parameter will automatically be rounded up to the next
multiple of 8 on 32-bit machines and 16 on 64-bit machines.
tune.chksize <number>
Sets the check buffer size to this size (in bytes). Higher values may help
find string or regex patterns in very large pages, though doing so may imply
more memory and CPU usage. The default value is 16384 and can be changed at
build time. It is not recommended to change this value, but to use better
checks whenever possible.
tune.comp.maxlevel <number>
Sets the maximum compression level. The compression level affects CPU
usage during compression. This value affects CPU usage during compression.
Each session using compression initializes the compression algorithm with
this value. The default value is 1.
tune.fail-alloc
If compiled with DEBUG_FAIL_ALLOC, gives the percentage of chances an
allocation attempt fails. Must be between 0 (no failure) and 100 (no
success). This is useful to debug and make sure memory failures are handled
gracefully.
tune.h2.header-table-size <number>
Sets the HTTP/2 dynamic header table size. It defaults to 4096 bytes and
cannot be larger than 65536 bytes. A larger value may help certain clients
send more compact requests, depending on their capabilities. This amount of
memory is consumed for each HTTP/2 connection. It is recommended not to
change it.
tune.h2.initial-window-size <number>
Sets the HTTP/2 initial window size, which is the number of bytes the client
can upload before waiting for an acknowledgment from haproxy. This setting
only affects payload contents (i.e. the body of POST requests), not headers.
The default value is 65535, which roughly allows up to 5 Mbps of upload
bandwidth per client over a network showing a 100 ms ping time, or 500 Mbps
over a 1-ms local network. It can make sense to increase this value to allow
faster uploads, or to reduce it to increase fairness when dealing with many
clients. It doesn't affect resource usage.
tune.h2.max-concurrent-streams <number>
Sets the HTTP/2 maximum number of concurrent streams per connection (ie the
number of outstanding requests on a single connection). The default value is
100. A larger one may slightly improve page load time for complex sites when
visited over high latency networks, but increases the amount of resources a
single client may allocate. A value of zero disables the limit so a single
client may create as many streams as allocatable by haproxy. It is highly
recommended not to change this value.
tune.h2.max-frame-size <number>
Sets the HTTP/2 maximum frame size that haproxy announces it is willing to
receive to its peers. The default value is the largest between 16384 and the
buffer size (tune.bufsize). In any case, haproxy will not announce support
for frame sizes larger than buffers. The main purpose of this setting is to
allow to limit the maximum frame size setting when using large buffers. Too
large frame sizes might have performance impact or cause some peers to
misbehave. It is highly recommended not to change this value.
tune.http.cookielen <number>
Sets the maximum length of captured cookies. This is the maximum value that
the "capture cookie xxx len yyy" will be allowed to take, and any upper value
will automatically be truncated to this one. It is important not to set too
high a value because all cookie captures still allocate this size whatever
their configured value (they share a same pool). This value is per request
per response, so the memory allocated is twice this value per connection.
When not specified, the limit is set to 63 characters. It is recommended not
to change this value.
tune.http.logurilen <number>
Sets the maximum length of request URI in logs. This prevents truncating long
request URIs with valuable query strings in log lines. This is not related
to syslog limits. If you increase this limit, you may also increase the
'log ... len yyy' parameter. Your syslog daemon may also need specific
configuration directives too.
The default value is 1024.
tune.http.maxhdr <number>
Sets the maximum number of headers in a request. When a request comes with a
number of headers greater than this value (including the first line), it is
rejected with a "400 Bad Request" status code. Similarly, too large responses
are blocked with "502 Bad Gateway". The default value is 101, which is enough
for all usages, considering that the widely deployed Apache server uses the
same limit. It can be useful to push this limit further to temporarily allow
a buggy application to work by the time it gets fixed. The accepted range is
1..32767. Keep in mind that each new header consumes 32bits of memory for
each session, so don't push this limit too high.
tune.idletimer <timeout>
Sets the duration after which haproxy will consider that an empty buffer is
probably associated with an idle stream. This is used to optimally adjust
some packet sizes while forwarding large and small data alternatively. The
decision to use splice() or to send large buffers in SSL is modulated by this
parameter. The value is in milliseconds between 0 and 65535. A value of zero
means that haproxy will not try to detect idle streams. The default is 1000,
which seems to correctly detect end user pauses (e.g. read a page before
clicking). There should be no reason for changing this value. Please check
tune.ssl.maxrecord below.
tune.listener.multi-queue { on | off }
Enables ('on') or disables ('off') the listener's multi-queue accept which
spreads the incoming traffic to all threads a "bind" line is allowed to run
on instead of taking them for itself. This provides a smoother traffic
distribution and scales much better, especially in environments where threads
may be unevenly loaded due to external activity (network interrupts colliding
with one thread for example). This option is enabled by default, but it may
be forcefully disabled for troubleshooting or for situations where it is
estimated that the operating system already provides a good enough
distribution and connections are extremely short-lived.
tune.lua.forced-yield <number>
This directive forces the Lua engine to execute a yield each <number> of
instructions executed. This permits interrupting a long script and allows the
HAProxy scheduler to process other tasks like accepting connections or
forwarding traffic. The default value is 10000 instructions. If HAProxy often
executes some Lua code but more responsiveness is required, this value can be
lowered. If the Lua code is quite long and its result is absolutely required
to process the data, the <number> can be increased.
tune.lua.maxmem
Sets the maximum amount of RAM in megabytes per process usable by Lua. By
default it is zero which means unlimited. It is important to set a limit to
ensure that a bug in a script will not result in the system running out of
memory.
tune.lua.session-timeout <timeout>
This is the execution timeout for the Lua sessions. This is useful for
preventing infinite loops or spending too much time in Lua. This timeout
counts only the pure Lua runtime. If the Lua does a sleep, the sleep is
not taken in account. The default timeout is 4s.
tune.lua.task-timeout <timeout>
Purpose is the same as "tune.lua.session-timeout", but this timeout is
dedicated to the tasks. By default, this timeout isn't set because a task may
remain alive during of the lifetime of HAProxy. For example, a task used to
check servers.
tune.lua.service-timeout <timeout>
This is the execution timeout for the Lua services. This is useful for
preventing infinite loops or spending too much time in Lua. This timeout
counts only the pure Lua runtime. If the Lua does a sleep, the sleep is
not taken in account. The default timeout is 4s.
tune.maxaccept <number>
Sets the maximum number of consecutive connections a process may accept in a
row before switching to other work. In single process mode, higher numbers
give better performance at high connection rates. However in multi-process
modes, keeping a bit of fairness between processes generally is better to
increase performance. This value applies individually to each listener, so
that the number of processes a listener is bound to is taken into account.
This value defaults to 64. In multi-process mode, it is divided by twice
the number of processes the listener is bound to. Setting this value to -1
completely disables the limitation. It should normally not be needed to tweak
this value.
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.
tune.maxrewrite <number>
Sets the reserved buffer space to this size in bytes. The reserved space is
used for header rewriting or appending. The first reads on sockets will never
fill more than bufsize-maxrewrite. Historically it has defaulted to half of
bufsize, though that does not make much sense since there are rarely large
numbers of headers to add. Setting it too high prevents processing of large
requests or responses. Setting it too low prevents addition of new headers
to already large requests or to POST requests. It is generally wise to set it
to about 1024. It is automatically readjusted to half of bufsize if it is
larger than that. This means you don't have to worry about it when changing
bufsize.
tune.pattern.cache-size <number>
Sets the size of the pattern lookup cache to <number> entries. This is an LRU
cache which reminds previous lookups and their results. It is used by ACLs
and maps on slow pattern lookups, namely the ones using the "sub", "reg",
"dir", "dom", "end", "bin" match methods as well as the case-insensitive
strings. It applies to pattern expressions which means that it will be able
to memorize the result of a lookup among all the patterns specified on a
configuration line (including all those loaded from files). It automatically
invalidates entries which are updated using HTTP actions or on the CLI. The
default cache size is set to 10000 entries, which limits its footprint to
about 5 MB per process/thread on 32-bit systems and 8 MB per process/thread
on 64-bit systems, as caches are thread/process local. There is a very low
risk of collision in this cache, which is in the order of the size of the
cache divided by 2^64. Typically, at 10000 requests per second with the
default cache size of 10000 entries, there's 1% chance that a brute force
attack could cause a single collision after 60 years, or 0.1% after 6 years.
This is considered much lower than the risk of a memory corruption caused by
aging components. If this is not acceptable, the cache can be disabled by
setting this parameter to 0.
tune.pipesize <number>
Sets the kernel pipe buffer size to this size (in bytes). By default, pipes
are the default size for the system. But sometimes when using TCP splicing,
it can improve performance to increase pipe sizes, especially if it is
suspected that pipes are not filled and that many calls to splice() are
performed. This has an impact on the kernel's memory footprint, so this must
not be changed if impacts are not understood.
tune.pool-low-fd-ratio <number>
This setting sets the max number of file descriptors (in percentage) used by
haproxy globally against the maximum number of file descriptors haproxy can
use before we stop putting connection into the idle pool for reuse. The
default is 20.
tune.pool-high-fd-ratio <number>
This setting sets the max number of file descriptors (in percentage) used by
haproxy globally against the maximum number of file descriptors haproxy can
use before we start killing idle connections when we can't reuse a connection
and we have to create a new one. The default is 25 (one quarter of the file
descriptor will mean that roughly half of the maximum front connections can
keep an idle connection behind, anything beyond this probably doesn't make
much sense in the general case when targeting connection reuse).
tune.rcvbuf.client <number>
tune.rcvbuf.server <number>
Forces the kernel socket receive buffer size on the client or the server side
to the specified value in bytes. This value applies to all TCP/HTTP frontends
and backends. It should normally never be set, and the default size (0) lets
the kernel auto-tune this value depending on the amount of available memory.
However it can sometimes help to set it to very low values (e.g. 4096) in
order to save kernel memory by preventing it from buffering too large amounts
of received data. Lower values will significantly increase CPU usage though.
tune.recv_enough <number>
HAProxy uses some hints to detect that a short read indicates the end of the
socket buffers. One of them is that a read returns more than <recv_enough>
bytes, which defaults to 10136 (7 segments of 1448 each). This default value
may be changed by this setting to better deal with workloads involving lots
of short messages such as telnet or SSH sessions.
tune.runqueue-depth <number>
Sets the maximum amount of task that can be processed at once when running
tasks. The default value is 200. Increasing it may incur latency when
dealing with I/Os, making it too small can incur extra overhead.
tune.sndbuf.client <number>
tune.sndbuf.server <number>
Forces the kernel socket send buffer size on the client or the server side to
the specified value in bytes. This value applies to all TCP/HTTP frontends
and backends. It should normally never be set, and the default size (0) lets
the kernel auto-tune this value depending on the amount of available memory.
However it can sometimes help to set it to very low values (e.g. 4096) in
order to save kernel memory by preventing it from buffering too large amounts
of received data. Lower values will significantly increase CPU usage though.
Another use case is to prevent write timeouts with extremely slow clients due
to the kernel waiting for a large part of the buffer to be read before
notifying haproxy again.
tune.ssl.cachesize <number>
Sets the size of the global SSL session cache, in a number of blocks. A block
is large enough to contain an encoded session without peer certificate.
An encoded session with peer certificate is stored in multiple blocks
depending on the size of the peer certificate. A block uses approximately
200 bytes of memory. The default value may be forced at build time, otherwise
defaults to 20000. When the cache is full, the most idle entries are purged
and reassigned. Higher values reduce the occurrence of such a purge, hence
the number of CPU-intensive SSL handshakes by ensuring that all users keep
their session as long as possible. All entries are pre-allocated upon startup
and are shared between all processes if "nbproc" is greater than 1. Setting
this value to 0 disables the SSL session cache.
tune.ssl.force-private-cache
This option disables SSL session cache sharing between all processes. It
should normally not be used since it will force many renegotiations due to
clients hitting a random process. But it may be required on some operating
systems where none of the SSL cache synchronization method may be used. In
this case, adding a first layer of hash-based load balancing before the SSL
layer might limit the impact of the lack of session sharing.
tune.ssl.lifetime <timeout>
Sets how long a cached SSL session may remain valid. This time is expressed
in seconds and defaults to 300 (5 min). It is important to understand that it
does not guarantee that sessions will last that long, because if the cache is
full, the longest idle sessions will be purged despite their configured
lifetime. The real usefulness of this setting is to prevent sessions from
being used for too long.
tune.ssl.maxrecord <number>
Sets the maximum amount of bytes passed to SSL_write() at a time. Default
value 0 means there is no limit. Over SSL/TLS, the client can decipher the
data only once it has received a full record. With large records, it means
that clients might have to download up to 16kB of data before starting to
process them. Limiting the value can improve page load times on browsers
located over high latency or low bandwidth networks. It is suggested to find
optimal values which fit into 1 or 2 TCP segments (generally 1448 bytes over
Ethernet with TCP timestamps enabled, or 1460 when timestamps are disabled),
keeping in mind that SSL/TLS add some overhead. Typical values of 1419 and
2859 gave good results during tests. Use "strace -e trace=write" to find the
best value. HAProxy will automatically switch to this setting after an idle
stream has been detected (see tune.idletimer above).
tune.ssl.default-dh-param <number>
Sets the maximum size of the Diffie-Hellman parameters used for generating
the ephemeral/temporary Diffie-Hellman key in case of DHE key exchange. The
final size will try to match the size of the server's RSA (or DSA) key (e.g,
a 2048 bits temporary DH key for a 2048 bits RSA key), but will not exceed
this maximum value. Default value if 1024. Only 1024 or higher values are
allowed. Higher values will increase the CPU load, and values greater than
1024 bits are not supported by Java 7 and earlier clients. This value is not
used if static Diffie-Hellman parameters are supplied either directly
in the certificate file or by using the ssl-dh-param-file parameter.
tune.ssl.ssl-ctx-cache-size <number>
Sets the size of the cache used to store generated certificates to <number>
entries. This is a LRU cache. Because generating a SSL certificate
dynamically is expensive, they are cached. The default cache size is set to
1000 entries.
tune.ssl.capture-cipherlist-size <number>
Sets the maximum size of the buffer used for capturing client-hello cipher
list. If the value is 0 (default value) the capture is disabled, otherwise
a buffer is allocated for each SSL/TLS connection.
tune.vars.global-max-size <size>
tune.vars.proc-max-size <size>
tune.vars.reqres-max-size <size>
tune.vars.sess-max-size <size>
tune.vars.txn-max-size <size>
These five tunes help to manage the maximum amount of memory used by the
variables system. "global" limits the overall amount of memory available for
all scopes. "proc" limits the memory for the process scope, "sess" limits the
memory for the session scope, "txn" for the transaction scope, and "reqres"
limits the memory for each request or response processing.
Memory accounting is hierarchical, meaning more coarse grained limits include
the finer grained ones: "proc" includes "sess", "sess" includes "txn", and
"txn" includes "reqres".
For example, when "tune.vars.sess-max-size" is limited to 100,
"tune.vars.txn-max-size" and "tune.vars.reqres-max-size" cannot exceed
100 either. If we create a variable "txn.var" that contains 100 bytes,
all available space is consumed.
Notice that exceeding the limits at runtime will not result in an error
message, but values might be cut off or corrupted. So make sure to accurately
plan for the amount of space needed to store all your variables.
tune.zlib.memlevel <number>
Sets the memLevel parameter in zlib initialization for each session. It
defines how much memory should be allocated for the internal compression
state. A value of 1 uses minimum memory but is slow and reduces compression
ratio, a value of 9 uses maximum memory for optimal speed. Can be a value
between 1 and 9. The default value is 8.
tune.zlib.windowsize <number>
Sets the window size (the size of the history buffer) as a parameter of the
zlib initialization for each session. Larger values of this parameter result
in better compression at the expense of memory usage. Can be a value between
8 and 15. The default value is 15.
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".
3.4. Userlists
--------------
It is possible to control access to frontend/backend/listen sections or to
http stats by allowing only authenticated and authorized users. To do this,
it is required to create at least one userlist and to define users.
userlist <listname>
Creates new userlist with name <listname>. Many independent userlists can be
used to store authentication & authorization data for independent customers.
group <groupname> [users <user>,<user>,(...)]
Adds group <groupname> to the current userlist. It is also possible to
attach users to this group by using a comma separated list of names
proceeded by "users" keyword.
user <username> [password|insecure-password <password>]
[groups <group>,<group>,(...)]
Adds user <username> to the current userlist. Both secure (encrypted) and
insecure (unencrypted) passwords can be used. Encrypted passwords are
evaluated using the crypt(3) function, so depending on the system's
capabilities, different algorithms are supported. For example, modern Glibc
based Linux systems support MD5, SHA-256, SHA-512, and, of course, the
classic DES-based method of encrypting passwords.
Attention: Be aware that using encrypted passwords might cause significantly
increased CPU usage, depending on the number of requests, and the algorithm
used. For any of the hashed variants, the password for each request must
be processed through the chosen algorithm, before it can be compared to the
value specified in the config file. Most current algorithms are deliberately
designed to be expensive to compute to achieve resistance against brute
force attacks. They do not simply salt/hash the clear text password once,
but thousands of times. This can quickly become a major factor in haproxy's
overall CPU consumption!
Example:
userlist L1
group G1 users tiger,scott
group G2 users xdb,scott
user tiger password $6$k6y3o.eP$JlKBx9za9667qe4(...)xHSwRv6J.C0/D7cV91
user scott insecure-password elgato
user xdb insecure-password hello
userlist L2
group G1
group G2
user tiger password $6$k6y3o.eP$JlKBx(...)xHSwRv6J.C0/D7cV91 groups G1
user scott insecure-password elgato groups G1,G2
user xdb insecure-password hello groups G2
Please note that both lists are functionally identical.
3.5. Peers
----------
It is possible to propagate entries of any data-types in stick-tables between
several haproxy instances over TCP connections in a multi-master fashion. Each
instance pushes its local updates and insertions to remote peers. The pushed
values overwrite remote ones without aggregation. Interrupted exchanges are
automatically detected and recovered from the last known point.
In addition, during a soft restart, the old process connects to the new one
using such a TCP connection to push all its entries before the new process
tries to connect to other peers. That ensures very fast replication during a
reload, it typically takes a fraction of a second even for large tables.
Note that Server IDs are used to identify servers remotely, so it is important
that configurations look similar or at least that the same IDs are forced on
each server on all participants.
peers <peersect>
Creates a new peer list with name <peersect>. It is an independent section,
which is referenced by one or more stick-tables.
bind [<address>]:<port_range> [, ...] [param*]
Defines the binding parameters of the local peer of this "peers" section.
Such lines are not supported with "peer" line in the same "peers" section.
disabled
Disables a peers section. It disables both listening and any synchronization
related to this section. This is provided to disable synchronization of stick
tables without having to comment out all "peers" references.
default-bind [param*]
Defines the binding parameters for the local peer, excepted its address.
default-server [param*]
Change default options for a server in a "peers" section.
Arguments:
<param*> is a list of parameters for this server. The "default-server"
keyword accepts an important number of options and has a complete
section dedicated to it. Please refer to section 5 for more
details.
See also: "server" and section 5 about server options
enable
This re-enables a disabled peers section which was previously disabled.
log <address> [len <length>] [format <format>] [sample <ranges>:<smp_size>]
<facility> [<level> [<minlevel>]]
"peers" sections support the same "log" keyword as for the proxies to
log information about the "peers" listener. See "log" option for proxies for
more details.
peer <peername> <ip>:<port> [param*]
Defines a peer inside a peers section.
If <peername> is set to the local peer name (by default hostname, or forced
using "-L" command line option), haproxy will listen for incoming remote peer
connection on <ip>:<port>. Otherwise, <ip>:<port> defines where to connect to
to join the remote peer, and <peername> is used at the protocol level to
identify and validate the remote peer on the server side.
During a soft restart, local peer <ip>:<port> is used by the old instance to
connect the new one and initiate a complete replication (teaching process).
It is strongly recommended to have the exact same peers declaration on all
peers and to only rely on the "-L" command line argument to change the local
peer name. This makes it easier to maintain coherent configuration files
across all peers.
You may want to reference some environment variables in the address
parameter, see section 2.3 about environment variables.
Note: "peer" keyword may transparently be replaced by "server" keyword (see
"server" keyword explanation below).
server <peername> [<ip>:<port>] [param*]
As previously mentioned, "peer" keyword may be replaced by "server" keyword
with a support for all "server" parameters found in 5.2 paragraph.
If the underlying peer is local, <ip>:<port> parameters must not be present.
These parameters must be provided on a "bind" line (see "bind" keyword
of this "peers" section).
Some of these parameters are irrelevant for "peers" sections.
Example:
# The old way.
peers mypeers
peer haproxy1 192.168.0.1:1024
peer haproxy2 192.168.0.2:1024
peer haproxy3 10.2.0.1:1024
backend mybackend
mode tcp
balance roundrobin
stick-table type ip size 20k peers mypeers
stick on src
server srv1 192.168.0.30:80
server srv2 192.168.0.31:80
Example:
peers mypeers
bind 127.0.0.11:10001 ssl crt mycerts/pem
default-server ssl verify none
server hostA 127.0.0.10:10000
server hostB #local peer
table <tablename> type {ip | integer | string [len <length>] | binary [len <length>]}
size <size> [expire <expire>] [nopurge] [store <data_type>]*
Configure a stickiness table for the current section. This line is parsed
exactly the same way as the "stick-table" keyword in others section, except
for the "peers" argument which is not required here and with an additional
mandatory first parameter to designate the stick-table. Contrary to others
sections, there may be several "table" lines in "peers" sections (see also
"stick-table" keyword).
Also be aware of the fact that "peers" sections have their own stick-table
namespaces to avoid collisions between stick-table names identical in
different "peers" section. This is internally handled prepending the "peers"
sections names to the name of the stick-tables followed by a '/' character.
If somewhere else in the configuration file you have to refer to such
stick-tables declared in "peers" sections you must use the prefixed version
of the stick-table name as follows:
peers mypeers
peer A ...
peer B ...
table t1 ...
frontend fe1
tcp-request content track-sc0 src table mypeers/t1
This is also this prefixed version of the stick-table names which must be
used to refer to stick-tables through the CLI.
About "peers" protocol, as only "peers" belonging to the same section may
communicate with each others, there is no need to do such a distinction.
Several "peers" sections may declare stick-tables with the same name.
This is shorter version of the stick-table name which is sent over the network.
There is only a '/' character as prefix to avoid stick-table name collisions between
stick-tables declared as backends and stick-table declared in "peers" sections
as follows in this weird but supported configuration:
peers mypeers
peer A ...
peer B ...
table t1 type string size 10m store gpc0
backend t1
stick-table type string size 10m store gpc0 peers mypeers
Here "t1" table declared in "mypeeers" section has "mypeers/t1" as global name.
"t1" table declared as a backend as "t1" as global name. But at peer protocol
level the former table is named "/t1", the latter is again named "t1".
3.6. Mailers
------------
It is possible to send email alerts when the state of servers changes.
If configured email alerts are sent to each mailer that is configured
in a mailers section. Email is sent to mailers using SMTP.
mailers <mailersect>
Creates a new mailer list with the name <mailersect>. It is an
independent section which is referenced by one or more proxies.
mailer <mailername> <ip>:<port>
Defines a mailer inside a mailers section.
Example:
mailers mymailers
mailer smtp1 192.168.0.1:587
mailer smtp2 192.168.0.2:587
backend mybackend
mode tcp
balance roundrobin
email-alert mailers mymailers
email-alert from test1@horms.org
email-alert to test2@horms.org
server srv1 192.168.0.30:80
server srv2 192.168.0.31:80
timeout mail <time>
Defines the time available for a mail/connection to be made and send to
the mail-server. If not defined the default value is 10 seconds. To allow
for at least two SYN-ACK packets to be send during initial TCP handshake it
is advised to keep this value above 4 seconds.
Example:
mailers mymailers
timeout mail 20s
mailer smtp1 192.168.0.1:587
3.7. Programs
-------------
In master-worker mode, it is possible to launch external binaries with the
master, these processes are called programs. These programs are launched and
managed the same way as the workers.
During a reload of HAProxy, those processes are dealing with the same
sequence as a worker:
- the master is re-executed
- the master sends a SIGUSR1 signal to the program
- if "option start-on-reload" is not disabled, the master launches a new
instance of the program
During a stop, or restart, a SIGTERM is sent to the programs.
program <name>
This is a new program section, this section will create an instance <name>
which is visible in "show proc" on the master CLI. (See "9.4. Master CLI" in
the management guide).
command <command> [arguments*]
Define the command to start with optional arguments. The command is looked
up in the current PATH if it does not include an absolute path. This is a
mandatory option of the program section. Arguments containing spaces must
be enclosed in quotes or double quotes or be prefixed by a backslash.
user <user name>
Changes the executed command user ID to the <user name> from /etc/passwd.
See also "group".
group <group name>
Changes the executed command group ID to the <group name> from /etc/group.
See also "user".
option start-on-reload
no option start-on-reload
Start (or not) a new instance of the program upon a reload of the master.
The default is to start a new instance. This option may only be used in a
program section.
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
bidirectional 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.
In HTTP mode, the processing applied to requests and responses flowing over
a connection depends in the combination of the frontend's HTTP options and
the backend's. HAProxy supports 4 connection modes :
- KAL : keep alive ("option http-keep-alive") which is the default mode : all
requests and responses are processed, and connections remain open but idle
between responses and new requests.
- SCL: server close ("option http-server-close") : the server-facing
connection is closed after the end of the response is received, but the
client-facing connection remains open.
- CLO: close ("option httpclose"): the connection is closed after the end of
the response and "Connection: close" appended in both directions.
The effective mode that will be applied to a connection passing through a
frontend and a backend can be determined by both proxy modes according to the
following matrix, but in short, the modes are symmetric, keep-alive is the
weakest option and close is the strongest.
Backend mode
| KAL | SCL | CLO
----+-----+-----+----
KAL | KAL | SCL | CLO
----+-----+-----+----
mode SCL | SCL | SCL | CLO
----+-----+-----+----
CLO | CLO | CLO | CLO
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
marked with "(*)" can be optionally inverted using the "no" prefix, e.g. "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
backlog X X X -
balance X - X X
bind - X X -
bind-process X X X X
capture cookie - X X -
capture request header - X X -
capture response header - X X -
compression X X X X
cookie X - X X
declare capture - X X -
default-server X - X X
default_backend X X X -
description - X X X
disabled X X X X
dispatch - - X X
email-alert from X X X X
email-alert level X X X X
email-alert mailers X X X X
email-alert myhostname X X X X
email-alert to X X X X
enabled X X X X
errorfile X X X X
errorloc X X X X
errorloc302 X X X X
-- keyword -------------------------- defaults - frontend - listen -- backend -
errorloc303 X X X X
force-persist - - X X
filter - X X X
fullconn X - X X
grace X X X X
hash-type X - X X
http-check disable-on-404 X - X X
http-check expect - - X X
http-check send-state X - X X
http-request - X X X
http-response - X X X
http-reuse X - X X
http-send-name-header - - X X
id - X X X
ignore-persist - - X X
load-server-state-from-file X - X X
log (*) X X X X
log-format X X X -
log-format-sd X X X -
log-tag X X X X
max-keep-alive-queue 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 -
option abortonclose (*) X - X X
option accept-invalid-http-request (*) X X X -
option accept-invalid-http-response (*) X - X X
option allbackups (*) X - X X
option checkcache (*) X - X X
option clitcpka (*) X X X -
option contstats (*) X X X -
option dontlog-normal (*) X X X -
option dontlognull (*) X X X -
-- keyword -------------------------- defaults - frontend - listen -- backend -
option forwardfor X X X X
option h1-case-adjust-bogus-client (*) X X X -
option h1-case-adjust-bogus-server (*) X - X X
option http-buffer-request (*) X X X X
option http-ignore-probes (*) X X X -
option http-keep-alive (*) X X X X
option http-no-delay (*) X X X X
option http-pretend-keepalive (*) X - X X
option http-server-close (*) X X X X
option http-use-proxy-header (*) X X X -
option httpchk X - X X
option httpclose (*) X X X X
option httplog X X X -
option http_proxy (*) X X X X
option independent-streams (*) X X X X
option ldap-check X - X X
option external-check X - X X
option log-health-checks (*) X - X X
option log-separate-errors (*) X X X -
option logasap (*) X X X -
option mysql-check X - X X
option nolinger (*) X X X X
option originalto X X X X
option persist (*) X - X X
option pgsql-check X - X X
option prefer-last-server (*) X - X X
option redispatch (*) X - X X
option redis-check X - X X
option smtpchk X - X X
option socket-stats (*) X X X -
option splice-auto (*) X X X X
option splice-request (*) X X X X
option splice-response (*) X X X X
option spop-check - - - X
option srvtcpka (*) X - X X
option ssl-hello-chk X - X X
-- keyword -------------------------- defaults - frontend - listen -- backend -
option tcp-check X - X X
option tcp-smart-accept (*) X X X -
option tcp-smart-connect (*) X - X X
option tcpka X X X X
option tcplog X X X X
option transparent (*) X - X X
external-check command X - X X
external-check path X - X X
persist rdp-cookie X - X X
rate-limit sessions X X X -
redirect - X X X
-- keyword -------------------------- defaults - frontend - listen -- backend -
retries X - X X
retry-on X - X X
server - - X X
server-state-file-name X - X X
server-template - - X X
source X - X X
stats admin - X X X
stats auth X X X X
stats enable X X X X
stats hide-version X X X X
stats http-request - X X X
stats realm X X X X
stats refresh X X X X
stats scope X X X X
stats show-desc X X X X
stats show-legends X X X X
stats show-node X X X X
stats uri X X X X
-- keyword -------------------------- defaults - frontend - listen -- backend -
stick match - - X X
stick on - - X X
stick store-request - - X X
stick store-response - - X X
stick-table - X X X
tcp-check connect - - X X
tcp-check expect - - X X
tcp-check send - - X X
tcp-check send-binary - - X X
tcp-request connection - X X -
tcp-request content - X X X
tcp-request inspect-delay - X X X
tcp-request session - X X -
tcp-response content - - X X
tcp-response inspect-delay - - X X
timeout check X - X X
timeout client X X X -
timeout client-fin X X X -
timeout connect X - X X
timeout http-keep-alive X X X X
timeout http-request X X X X
timeout queue X - X X
timeout server X - X X
timeout server-fin X - X X
timeout tarpit X X X X
timeout tunnel X - X X
transparent (deprecated) X - X X
unique-id-format X X X -
unique-id-header X X X -
use_backend - X X -
use-fcgi-app - - X X
use-server - - 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.
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]
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. It is limited by
design to 4095 active servers per backend. Note that in some
large farms, when a server becomes up after having been down
for a very short time, it may sometimes take a few hundreds
requests for it to be re-integrated into the farm and start
receiving traffic. This is normal, though very rare. It is
indicated here in case you would have the chance to observe
it, so that you don't worry.
static-rr Each server is used in turns, according to their weights.
This algorithm is as similar to roundrobin except that it is
static, which means that changing a server's weight on the
fly will have no effect. On the other hand, it has no design
limitation on the number of servers, and when a server goes
up, it is always immediately reintroduced into the farm, once
the full map is recomputed. It also uses slightly less CPU to
run (around -1%).
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.
first The first server with available connection slots receives the
connection. The servers are chosen from the lowest numeric
identifier to the highest (see server parameter "id"), which
defaults to the server's position in the farm. Once a server
reaches its maxconn value, the next server is used. It does
not make sense to use this algorithm without setting maxconn.
The purpose of this algorithm is to always use the smallest
number of servers so that extra servers can be powered off
during non-intensive hours. This algorithm ignores the server
weight, and brings more benefit to long session such as RDP
or IMAP than HTTP, though it can be useful there too. In
order to use this algorithm efficiently, it is recommended
that a cloud controller regularly checks server usage to turn
them off when unused, and regularly checks backend queue to
turn new servers on when the queue inflates. Alternatively,
using "http-check send-state" may inform servers on the load.
source The source IP address is hashed and divided by the total
weight of the running servers to designate which server will
receive the request. This ensures that the same client IP
address will always reach the same server as long as no
server goes down or up. If the hash result changes due to the
number of running servers changing, many clients will be
directed to a different server. This algorithm is generally
used in TCP mode where no cookie may be inserted. It may also
be used on the Internet to provide a best-effort stickiness
to clients which refuse session cookies. This algorithm is
static by default, which means that changing a server's
weight on the fly will have no effect, but this can be
changed using "hash-type".
uri This algorithm hashes either the left part of the URI (before
the question mark) or the whole URI (if the "whole" parameter
is present) and divides the hash value by the total weight of
the running servers. The result designates which server will
receive the request. This ensures that the same URI will
always be directed to the same server as long as no server
goes up or down. This is used with proxy caches and
anti-virus proxies in order to maximize the cache hit rate.
Note that this algorithm may only be used in an HTTP backend.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
This algorithm supports two optional parameters "len" and
"depth", both followed by a positive integer number. These
options may be helpful when it is needed to balance servers
based on the beginning of the URI only. The "len" parameter
indicates that the algorithm should only consider that many
characters at the beginning of the URI to compute the hash.
Note that having "len" set to 1 rarely makes sense since most
URIs start with a leading "/".
The "depth" parameter indicates the maximum directory depth
to be used to compute the hash. One level is counted for each
slash in the request. If both parameters are specified, the
evaluation stops when either is reached.
url_param The URL parameter specified in argument will be looked up in
the query string of each HTTP GET request.
If the modifier "check_post" is used, then an HTTP POST
request entity will be searched for the parameter argument,
when it is not found in a query string after a question mark
('?') in the URL. The message body will only start to be
analyzed once either the advertised amount of data has been
received or the request buffer is full. In the unlikely event
that chunked encoding is used, only the first chunk is
scanned. Parameter values separated by a chunk boundary, may
be randomly balanced if at all. This keyword used to support
an optional <max_wait> parameter which is now ignored.
If the parameter is found followed by an equal sign ('=') and
a value, then the value is hashed and divided by the total
weight of the running servers. The result designates which
server will receive the request.
This is used to track user identifiers in requests and ensure
that a same user ID will always be sent to the same server as
long as no server goes up or down. If no value is found or if
the parameter is not found, then a round robin algorithm is
applied. Note that this algorithm may only be used in an HTTP
backend. This algorithm is static by default, which means
that changing a server's weight on the fly will have no
effect, but this can be changed using "hash-type".
hdr(<name>) The HTTP header <name> will be looked up in each HTTP
request. Just as with the equivalent ACL 'hdr()' function,
the header name in parenthesis is not case sensitive. If the
header is absent or if it does not contain any value, the
roundrobin algorithm is applied instead.
An optional 'use_domain_only' parameter is available, for
reducing the hash algorithm to the main domain part with some
specific headers such as 'Host'. For instance, in the Host
value "haproxy.1wt.eu", only "1wt" will be considered.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
random
random(<draws>)
A random number will be used as the key for the consistent
hashing function. This means that the servers' weights are
respected, dynamic weight changes immediately take effect, as
well as new server additions. Random load balancing can be
useful with large farms or when servers are frequently added
or removed as it may avoid the hammering effect that could
result from roundrobin or leastconn in this situation. The
hash-balance-factor directive can be used to further improve
fairness of the load balancing, especially in situations
where servers show highly variable response times. When an
argument <draws> is present, it must be an integer value one
or greater, indicating the number of draws before selecting
the least loaded of these servers. It was indeed demonstrated
that picking the least loaded of two servers is enough to
significantly improve the fairness of the algorithm, by
always avoiding to pick the most loaded server within a farm
and getting rid of any bias that could be induced by the
unfair distribution of the consistent list. Higher values N
will take away N-1 of the highest loaded servers at the
expense of performance. With very high values, the algorithm
will converge towards the leastconn's result but much slower.
The default value is 2, which generally shows very good
distribution and performance. This algorithm is also known as
the Power of Two Random Choices and is described here :
http://www.eecs.harvard.edu/~michaelm/postscripts/handbook2001.pdf
rdp-cookie
rdp-cookie(<name>)
The RDP cookie <name> (or "mstshash" if omitted) will be
looked up and hashed for each incoming TCP request. Just as
with the equivalent ACL 'req_rdp_cookie()' function, the name
is not case-sensitive. This mechanism is useful as a degraded
persistence mode, as it makes it possible to always send the
same user (or the same session ID) to the same server. If the
cookie is not found, the normal roundrobin algorithm is
used instead.
Note that for this to work, the frontend must ensure that an
RDP cookie is already present in the request buffer. For this
you must use 'tcp-request content accept' rule combined with
a 'req_rdp_cookie_cnt' ACL.
This algorithm is static by default, which means that
changing a server's weight on the fly will have no effect,
but this can be changed using "hash-type".
See also the rdp_cookie pattern fetch function.
<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.
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.
With authentication schemes that require the same connection like NTLM, URI
based algorithms must not be used, as they would cause subsequent requests
to be routed to different backend servers, breaking the invalid assumptions
NTLM relies on.
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 eligible for consideration, because there is no way
to determine if the parameters will be found in the body or entity which
may contain binary data. Therefore another method may be required to
restrict consideration of POST requests that have no URL parameters in
the body. (see acl http_end)
- using a <max_wait> value larger than the request buffer size does not
make sense and is useless. The buffer size is set at build time, and
defaults to 16 kB.
- Content-Encoding is not supported, the parameter search will probably
fail; and load balancing will fall back to Round Robin.
- Expect: 100-continue is not supported, load balancing will fall back to
Round Robin.
- Transfer-Encoding (RFC7230 3.3.1) is only supported in the first chunk.
If the entire parameter value is not present in the first chunk, the
selection of server is undefined (actually, defined by how little
actually appeared in the first chunk).
- This feature does not support generation of a 100, 411 or 501 response.
- In some cases, requesting "check_post" MAY attempt to scan the entire
contents of a message body. Scanning normally terminates when linear
white space or control characters are found, indicating the end of what
might be a URL parameter list. This is probably not a concern with SGML
type message bodies.
See also : "dispatch", "cookie", "transparent", "hash-type" and "http_proxy".
bind [<address>]:<port_range> [, ...] [param*]
bind /<path> [, ...] [param*]
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". The IPv6 equivalent is '::'.
Optionally, an address family prefix may be used before the
address to force the family regardless of the address format,
which can be useful to specify a path to a unix socket with
no slash ('/'). Currently supported prefixes are :
- 'ipv4@' -> address is always IPv4
- 'ipv6@' -> address is always IPv6
- 'unix@' -> address is a path to a local unix socket
- 'abns@' -> address is in abstract namespace (Linux only).
Note: since abstract sockets are not "rebindable", they
do not cope well with multi-process mode during
soft-restart, so it is better to avoid them if
nbproc is greater than 1. The effect is that if the
new process fails to start, only one of the old ones
will be able to rebind to the socket.
- 'fd@<n>' -> use file descriptor <n> inherited from the
parent. The fd must be bound and may or may not already
be listening.
- 'sockpair@<n>'-> like fd@ but you must use the fd of a
connected unix socket or of a socketpair. The bind waits
to receive a FD over the unix socket and uses it as if it
was the FD of an accept(). Should be used carefully.
You may want to reference some environment variables in the
address parameter, see section 2.3 about environment
variables.
<port_range> is either a unique TCP port, or a port range for which the
proxy will accept connections for the IP address specified
above. The port is mandatory for TCP listeners. Note that in
the case of an IPv6 address, the port is always the number
after the last colon (':'). A range can either be :
- a numerical port (ex: '80')
- a dash-delimited ports range explicitly stating the lower
and upper bounds (ex: '2000-2100') which are included in
the range.
Particular care must be taken against port ranges, because
every <address:port> couple consumes one socket (= a file
descriptor), so it's easy to consume lots of descriptors
with a simple range, and to run out of sockets. Also, each
<address:port> couple must be used only once among all
instances running on a same system. Please note that binding
to ports lower than 1024 generally require particular
privileges to start the program, which are independent of
the 'uid' parameter.
<path> is a UNIX socket path beginning with a slash ('/'). This is
alternative to the TCP listening port. HAProxy will then
receive UNIX connections on the socket located at this place.
The path must begin with a slash and by default is absolute.
It can be relative to the prefix defined by "unix-bind" in
the global section. Note that the total length of the prefix
followed by the socket path cannot exceed some system limits
for UNIX sockets, which commonly are set to 107 characters.
<param*> is a list of parameters common to all sockets declared on the
same line. These numerous parameters depend on OS and build
options and have a complete section dedicated to them. Please
refer to section 5 to for more details.
It is possible to specify a list of address:port combinations delimited by
commas. The frontend will then listen on all of these addresses. There is no
fixed limit to the number of addresses and ports which can be listened on in
a frontend, as well as there is no limit to the number of "bind" statements
in a frontend.
Example :
listen http_proxy
bind :80,:443
bind 10.0.0.1:10080,10.0.0.1:10443
bind /var/run/ssl-frontend.sock user root mode 600 accept-proxy
listen http_https_proxy
bind :80
bind :443 ssl crt /etc/haproxy/site.pem
listen http_https_proxy_explicit
bind ipv6@:80
bind ipv4@public_ssl:443 ssl crt /etc/haproxy/site.pem
bind unix@ssl-frontend.sock user root mode 600 accept-proxy
listen external_bind_app1
bind "fd@${FD_APP1}"
Note: regarding Linux's abstract namespace sockets, HAProxy uses the whole
sun_path length is used for the address length. Some other programs
such as socat use the string length only by default. Pass the option
",unix-tightsocklen=0" to any abstract socket definition in socat to
make it compatible with HAProxy's.
See also : "source", "option forwardfor", "unix-bind" and the PROXY protocol
documentation, and section 5 about bind options.
bind-process [ all | odd | even | <process_num>[-[<process_num>]] ] ...
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,...63. This
option may be combined with other numbers.
even This instance will be enabled on processes 2,4,6,...64. 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.
process_num The instance will be enabled on this process number or range,
whose values must all be between 1 and 32 or 64 depending on
the machine's word size. Ranges can be partially defined. The
higher bound can be omitted. In such case, it is replaced by
the corresponding maximum value. If a proxy is bound to
process numbers greater than the configured global.nbproc, it
will either be forced to process #1 if a single process was
specified, or to all processes otherwise.
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 or 64 processes
using this keyword, but this should be more than enough for most setups.
Please note that 'all' really means all processes regardless of the machine's
word size, and is not limited to the first 32 or 64.
Each "bind" line may further be limited to a subset of the proxy's processes,
please consult the "process" bind keyword in section 5.1.
When a frontend has no explicit "bind-process" line, it tries to bind to all
the processes referenced by its "bind" lines. That means that frontends can
easily adapt to their listeners' processes.
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
listen management
bind 10.0.0.4:80
bind-process 1-4
See also : "nbproc" in global section, and "process" in section 5.1.
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 (e.g. ASPSESSIONXXX).
<length> is the maximum number of characters to report in the logs, which
include the cookie name, the equal sign and the value, all in the
standard "name=value" form. The string will be truncated on the
right if it exceeds <length>.
Only the first cookie is captured. Both the "cookie" request headers and the
"set-cookie" response headers are monitored. This is particularly useful to
check for application bugs causing session crossing or stealing between
users, because generally the user's cookies can only change on a login page.
When the cookie was not presented by the client, the associated log column
will report "-". When a request does not cause a cookie to be assigned by the
server, a "-" is reported in the response column.
The capture is performed in the frontend only because it is necessary that
the log format does not change for a given frontend depending on the
backends. This may change in the future. Note that there can be only one
"capture cookie" statement in a frontend. The maximum capture length is set
by the global "tune.http.cookielen" setting and defaults to 63 characters. It
is not possible to specify a capture in a "defaults" section.
Example:
capture cookie ASPSESSION len 32
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 last 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>.
The complete value of the last occurrence of the header is captured. The
value will be added to the logs between braces ('{}'). If multiple headers
are captured, they will be delimited by a vertical bar ('|') and will appear
in the same order they were declared in the configuration. Non-existent
headers will be logged just as an empty string. Common uses for request
header captures include the "Host" field in virtual hosting environments, the
"Content-length" when uploads are supported, "User-agent" to quickly
differentiate between real users and robots, and "X-Forwarded-For" in proxied
environments to find where the request came from.
Note that when capturing headers such as "User-agent", some spaces may be
logged, making the log analysis more difficult. Thus be careful about what
you log if you know your log parser is not smart enough to rely on the
braces.
There is no limit to the number of captured request headers nor to their
length, though it is wise to keep them low to limit memory usage per session.
In order to keep log format consistent for a same frontend, header captures
can only be declared in a frontend. It is not possible to specify a capture
in a "defaults" section.
Example:
capture request header Host len 15
capture request header X-Forwarded-For len 15
capture request header Referer len 15
See also : "capture cookie", "capture response header" as well as section 8
about logging.
capture response header <name> len <length>
Capture and log the last 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>.
The complete value of the last occurrence of the header is captured. The
result will be added to the logs between braces ('{}') after the captured
request headers. If multiple headers are captured, they will be delimited by
a vertical bar ('|') and will appear in the same order they were declared in
the configuration. Non-existent headers will be logged just as an empty
string. Common uses for response header captures include the "Content-length"
header which indicates how many bytes are expected to be returned, the
"Location" header to track redirections.
There is no limit to the number of captured response headers nor to their
length, though it is wise to keep them low to limit memory usage per session.
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.
compression algo <algorithm> ...
compression type <mime type> ...
compression offload
Enable HTTP compression.
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
algo is followed by the list of supported compression algorithms.
type is followed by the list of MIME types that will be compressed.
offload makes haproxy work as a compression offloader only (see notes).
The currently supported algorithms are :
identity this is mostly for debugging, and it was useful for developing
the compression feature. Identity does not apply any change on
data.
gzip applies gzip compression. This setting is only available when
support for zlib or libslz was built in.
deflate same as "gzip", but with deflate algorithm and zlib format.
Note that this algorithm has ambiguous support on many
browsers and no support at all from recent ones. It is
strongly recommended not to use it for anything else than
experimentation. This setting is only available when support
for zlib or libslz was built in.
raw-deflate same as "deflate" without the zlib wrapper, and used as an
alternative when the browser wants "deflate". All major
browsers understand it and despite violating the standards,
it is known to work better than "deflate", at least on MSIE
and some versions of Safari. Do not use it in conjunction
with "deflate", use either one or the other since both react
to the same Accept-Encoding token. This setting is only
available when support for zlib or libslz was built in.
Compression will be activated depending on the Accept-Encoding request
header. With identity, it does not take care of that header.
If backend servers support HTTP compression, these directives
will be no-op: haproxy will see the compressed response and will not
compress again. If backend servers do not support HTTP compression and
there is Accept-Encoding header in request, haproxy will compress the
matching response.
The "offload" setting makes haproxy remove the Accept-Encoding header to
prevent backend servers from compressing responses. It is strongly
recommended not to do this because this means that all the compression work
will be done on the single point where haproxy is located. However in some
deployment scenarios, haproxy may be installed in front of a buggy gateway
with broken HTTP compression implementation which can't be turned off.
In that case haproxy can be used to prevent that gateway from emitting
invalid payloads. In this case, simply removing the header in the
configuration does not work because it applies before the header is parsed,
so that prevents haproxy from compressing. The "offload" setting should
then be used for such scenarios. Note: for now, the "offload" setting is
ignored when set in a defaults section.
Compression is disabled when:
* the request does not advertise a supported compression algorithm in the
"Accept-Encoding" header
* the response message is not HTTP/1.1
* HTTP status code is not one of 200, 201, 202, or 203
* response contain neither a "Content-Length" header nor a
"Transfer-Encoding" whose last value is "chunked"
* response contains a "Content-Type" header whose first value starts with
"multipart"
* the response contains the "no-transform" value in the "Cache-control"
header
* User-Agent matches "Mozilla/4" unless it is MSIE 6 with XP SP2, or MSIE 7
and later
* The response contains a "Content-Encoding" header, indicating that the
response is already compressed (see compression offload)
* The response contains an invalid "ETag" header or multiple ETag headers
Note: The compression does not emit the Warning header.
Examples :
compression algo gzip
compression type text/html text/plain
cookie <name> [ rewrite | insert | prefix ] [ indirect ] [ nocache ]
[ postonly ] [ preserve ] [ httponly ] [ secure ]
[ domain <domain> ]* [ maxidle <idle> ] [ maxlife <life> ]
[ dynamic ]
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 (e.g.
HTTP/HTTPS), care should be taken to use different cookie names
between all backends if persistence between them is not desired.
rewrite This keyword indicates that the cookie will be provided by the
server and that haproxy will have to modify its value to set the
server's identifier in it. This mode is handy when the management
of complex combinations of "Set-cookie" and "Cache-control"
headers is left to the application. The application can then
decide whether or not it is appropriate to emit a persistence
cookie. Since all responses should be monitored, this mode
doesn't work in HTTP tunnel mode. Unless the application
behavior is very complex and/or broken, it is advised not to
start with this mode for new deployments. This keyword is
incompatible with "insert" and "prefix".
insert This keyword indicates that the persistence cookie will have to
be inserted by haproxy in server responses if the client did not
already have a cookie that would have permitted it to access this
server. When used without the "preserve" option, if the server
emits a cookie with the same name, it will be removed before
processing. For this reason, this mode can be used to upgrade
existing configurations running in the "rewrite" mode. The cookie
will only be a session cookie and will not be stored on the
client's disk. By default, unless the "indirect" option is added,
the server will see the cookies emitted by the client. Due to
caching effects, it is generally wise to add the "nocache" or
"postonly" keywords (see below). The "insert" keyword is not
compatible with "rewrite" and "prefix".
prefix This keyword indicates that instead of relying on a dedicated
cookie for the persistence, an existing one will be completed.
This may be needed in some specific environments where the client
does not support more than one single cookie and the application
already needs it. In this case, whenever the server sets a cookie
named <name>, it will be prefixed with the server's identifier
and a delimiter. The prefix will be removed from all client
requests so that the server still finds the cookie it emitted.
Since all requests and responses are subject to being modified,
this mode doesn't work with tunnel mode. The "prefix" keyword is
not compatible with "rewrite" and "insert". Note: it is highly
recommended not to use "indirect" with "prefix", otherwise server
cookie updates would not be sent to clients.
indirect When this option is specified, no cookie will be emitted to a
client which already has a valid one for the server which has
processed the request. If the server sets such a cookie itself,
it will be removed, unless the "preserve" option is also set. In
"insert" mode, this will additionally remove cookies from the
requests transmitted to the server, making the persistence
mechanism totally transparent from an application point of view.
Note: it is highly recommended not to use "indirect" with
"prefix", otherwise server cookie updates would not be sent to
clients.
nocache This option is recommended in conjunction with the insert mode
when there is a cache between the client and HAProxy, as it
ensures that a cacheable response will be tagged non-cacheable if
a cookie needs to be inserted. This is important because if all
persistence cookies are added on a cacheable home page for
instance, then all customers will then fetch the page from an
outer cache and will all share the same persistence cookie,
leading to one server receiving much more traffic than others.
See also the "insert" and "postonly" options.
postonly This option ensures that cookie insertion will only be performed
on responses to POST requests. It is an alternative to the
"nocache" option, because POST responses are not cacheable, so
this ensures that the persistence cookie will never get cached.
Since most sites do not need any sort of persistence before the
first POST which generally is a login request, this is a very
efficient method to optimize caching without risking to find a
persistence cookie in the cache.
See also the "insert" and "nocache" options.
preserve This option may only be used with "insert" and/or "indirect". It
allows the server to emit the persistence cookie itself. In this
case, if a cookie is found in the response, haproxy will leave it
untouched. This is useful in order to end persistence after a
logout request for instance. For this, the server just has to
emit a cookie with an invalid value (e.g. empty) or with a date in
the past. By combining this mechanism with the "disable-on-404"
check option, it is possible to perform a completely graceful
shutdown because users will definitely leave the server after
they logout.
httponly This option tells haproxy to add an "HttpOnly" cookie attribute
when a cookie is inserted. This attribute is used so that a
user agent doesn't share the cookie with non-HTTP components.
Please check RFC6265 for more information on this attribute.
secure This option tells haproxy to add a "Secure" cookie attribute when
a cookie is inserted. This attribute is used so that a user agent
never emits this cookie over non-secure channels, which means
that a cookie learned with this flag will be presented only over
SSL/TLS connections. Please check RFC6265 for more information on
this attribute.
domain This option allows to specify the domain at which a cookie is
inserted. It requires exactly one parameter: a valid domain
name. If the domain begins with a dot, the browser is allowed to
use it for any host ending with that name. It is also possible to
specify several domain names by invoking this option multiple
times. Some browsers might have small limits on the number of
domains, so be careful when doing that. For the record, sending
10 domains to MSIE 6 or Firefox 2 works as expected.
maxidle This option allows inserted cookies to be ignored after some idle
time. It only works with insert-mode cookies. When a cookie is
sent to the client, the date this cookie was emitted is sent too.
Upon further presentations of this cookie, if the date is older
than the delay indicated by the parameter (in seconds), it will
be ignored. Otherwise, it will be refreshed if needed when the
response is sent to the client. This is particularly useful to
prevent users who never close their browsers from remaining for
too long on the same server (e.g. after a farm size change). When
this option is set and a cookie has no date, it is always
accepted, but gets refreshed in the response. This maintains the
ability for admins to access their sites. Cookies that have a
date in the future further than 24 hours are ignored. Doing so
lets admins fix timezone issues without risking kicking users off
the site.
maxlife This option allows inserted cookies to be ignored after some life
time, whether they're in use or not. It only works with insert
mode cookies. When a cookie is first sent to the client, the date
this cookie was emitted is sent too. Upon further presentations
of this cookie, if the date is older than the delay indicated by
the parameter (in seconds), it will be ignored. If the cookie in
the request has no date, it is accepted and a date will be set.
Cookies that have a date in the future further than 24 hours are
ignored. Doing so lets admins fix timezone issues without risking
kicking users off the site. Contrary to maxidle, this value is
not refreshed, only the first visit date counts. Both maxidle and
maxlife may be used at the time. This is particularly useful to
prevent users who never close their browsers from remaining for
too long on the same server (e.g. after a farm size change). This
is stronger than the maxidle method in that it forces a
redispatch after some absolute delay.
dynamic Activate dynamic cookies. When used, a session cookie is
dynamically created for each server, based on the IP and port
of the server, and a secret key, specified in the
"dynamic-cookie-key" backend directive.
The cookie will be regenerated each time the IP address change,
and is only generated for IPv4/IPv6.
There can be only one persistence cookie per HTTP backend, and it can be
declared in a defaults section. The value of the cookie will be the value
indicated after the "cookie" keyword in a "server" statement. If no cookie
is declared for a given server, the cookie is not set.
Examples :
cookie JSESSIONID prefix
cookie SRV insert indirect nocache
cookie SRV insert postonly indirect
cookie SRV insert indirect nocache maxidle 30m maxlife 8h
See also : "balance source", "capture cookie", "server" and "ignore-persist".
declare capture [ request | response ] len <length>
Declares a capture slot.
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | no
Arguments:
<length> is the length allowed for the capture.
This declaration is only available in the frontend or listen section, but the
reserved slot can be used in the backends. The "request" keyword allocates a
capture slot for use in the request, and "response" allocates a capture slot
for use in the response.
See also: "capture-req", "capture-res" (sample converters),
"capture.req.hdr", "capture.res.hdr" (sample fetches),
"http-request capture" and "http-response capture".
default-server [param*]
Change default options for a server in a backend
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
Arguments:
<param*> is a list of parameters for this server. The "default-server"
keyword accepts an important number of options and has a complete
section dedicated to it. Please refer to section 5 for more
details.
Example :
default-server inter 1000 weight 13
See also: "server" and section 5 about server options
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"
description <string>
Describe a listen, frontend or backend.
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments : string
Allows to add a sentence to describe the related object in the HAProxy HTML
stats page. The description will be printed on the right of the object name
it describes.
No need to backslash spaces in the <string> arguments.
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"
dispatch <address>:<port>
Set a default server address
May be used in sections : defaults | frontend | listen | backend
no | no | yes | yes
Arguments :
<address> is the IPv4 address of the default server. Alternatively, a
resolvable hostname is supported, but this name will be resolved
during start-up.
<ports> is a mandatory port specification. All connections will be sent
to this port, and it is not permitted to use port offsets as is
possible with normal servers.
The "dispatch" keyword designates a default server for use when no other
server can take the connection. In the past it was used to forward non
persistent connections to an auxiliary load balancer. Due to its simple
syntax, it has also been used for simple TCP relays. It is recommended not to
use it for more clarity, and to use the "server" directive instead.
See also : "server"
dynamic-cookie-key <string>
Set the dynamic cookie secret key for a backend.
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
Arguments : The secret key to be used.
When dynamic cookies are enabled (see the "dynamic" directive for cookie),
a dynamic cookie is created for each server (unless one is explicitly
specified on the "server" line), using a hash of the IP address of the
server, the TCP port, and the secret key.
That way, we can ensure session persistence across multiple load-balancers,
even if servers are dynamically added or removed.
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 200, 400, 403, 405, 408, 425, 429, 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.
Code 200 is emitted in response to requests matching a "monitor-uri" rule.
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 (e.g. images) in order to avoid
loops between the client and HAProxy when all servers are down, causing an
error to be returned instead of an image. 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 408 /dev/null # work around Chrome pre-connect bug
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 200, 400, 403, 405, 408, 425, 429, 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 (e.g. 500).
It is important to understand that this keyword is not meant to rewrite
errors returned by the server, but errors detected and returned by HAProxy.
This is why the list of supported errors is limited to a small set.
Code 200 is emitted in response to requests matching a "monitor-uri" rule.
Note that both keyword return the HTTP 302 status code, which tells the
client to fetch the designated URL using the same HTTP method. This can be
quite problematic in case of non-GET methods such as POST, because the URL
sent to the client might not be allowed for something other than GET. To
work around this problem, please use "errorloc303" which send the HTTP 303
status code, indicating to the client that the URL must be fetched with a GET
request.
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 200, 400, 403, 405, 408, 425, 429, 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 (e.g. 500).
It is important to understand that this keyword is not meant to rewrite
errors returned by the server, but errors detected and returned by HAProxy.
This is why the list of supported errors is limited to a small set.
Code 200 is emitted in response to requests matching a "monitor-uri" rule.
Note that both keyword return the HTTP 303 status code, which tells the
client to fetch the designated URL using the same HTTP GET method. This
solves the usual problems associated with "errorloc" and the 302 code. It is
possible that some very old browsers designed before HTTP/1.1 do not support
it, but no such problem has been reported till now.
See also : "errorfile", "errorloc", "errorloc302"
email-alert from <emailaddr>
Declare the from email address to be used in both the envelope and header
of email alerts. This is the address that email alerts are sent from.
May be used in sections: defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
<emailaddr> is the from email address to use when sending email alerts
Also requires "email-alert mailers" and "email-alert to" to be set
and if so sending email alerts is enabled for the proxy.
See also : "email-alert level", "email-alert mailers",
"email-alert myhostname", "email-alert to", section 3.6 about
mailers.
email-alert level <level>
Declare the maximum log level of messages for which email alerts will be
sent. This acts as a filter on the sending of email alerts.
May be used in sections: defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
<level> One of the 8 syslog levels:
emerg alert crit err warning notice info debug
The above syslog levels are ordered from lowest to highest.
By default level is alert
Also requires "email-alert from", "email-alert mailers" and
"email-alert to" to be set and if so sending email alerts is enabled
for the proxy.
Alerts are sent when :
* An un-paused server is marked as down and <level> is alert or lower
* A paused server is marked as down and <level> is notice or lower
* A server is marked as up or enters the drain state and <level>
is notice or lower
* "option log-health-checks" is enabled, <level> is info or lower,
and a health check status update occurs
See also : "email-alert from", "email-alert mailers",
"email-alert myhostname", "email-alert to",
section 3.6 about mailers.
email-alert mailers <mailersect>
Declare the mailers to be used when sending email alerts
May be used in sections: defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
<mailersect> is the name of the mailers section to send email alerts.
Also requires "email-alert from" and "email-alert to" to be set
and if so sending email alerts is enabled for the proxy.
See also : "email-alert from", "email-alert level", "email-alert myhostname",
"email-alert to", section 3.6 about mailers.
email-alert myhostname <hostname>
Declare the to hostname address to be used when communicating with
mailers.
May be used in sections: defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
<hostname> is the hostname to use when communicating with mailers
By default the systems hostname is used.
Also requires "email-alert from", "email-alert mailers" and
"email-alert to" to be set and if so sending email alerts is enabled
for the proxy.
See also : "email-alert from", "email-alert level", "email-alert mailers",
"email-alert to", section 3.6 about mailers.
email-alert to <emailaddr>
Declare both the recipient address in the envelope and to address in the
header of email alerts. This is the address that email alerts are sent to.
May be used in sections: defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments :
<emailaddr> is the to email address to use when sending email alerts
Also requires "email-alert mailers" and "email-alert to" to be set
and if so sending email alerts is enabled for the proxy.
See also : "email-alert from", "email-alert level", "email-alert mailers",
"email-alert myhostname", section 3.6 about mailers.
force-persist { if | unless } <condition>
Declare a condition to force persistence on down servers
May be used in sections: defaults | frontend | listen | backend
no | no | yes | yes
By default, requests are not dispatched to down servers. It is possible to
force this using "option persist", but it is unconditional and redispatches
to a valid server if "option redispatch" is set. That leaves with very little
possibilities to force some requests to reach a server which is artificially
marked down for maintenance operations.
The "force-persist" statement allows one to declare various ACL-based
conditions which, when met, will cause a request to ignore the down status of
a server and still try to connect to it. That makes it possible to start a
server, still replying an error to the health checks, and run a specially
configured browser to test the service. Among the handy methods, one could
use a specific source IP address, or a specific cookie. The cookie also has
the advantage that it can easily be added/removed on the browser from a test
page. Once the service is validated, it is then possible to open the service
to the world by returning a valid response to health checks.
The forced persistence is enabled when an "if" condition is met, or unless an
"unless" condition is met. The final redispatch is always disabled when this
is used.
See also : "option redispatch", "ignore-persist", "persist",
and section 7 about ACL usage.
filter <name> [param*]
Add the filter <name> in the filter list attached to the proxy.
May be used in sections : defaults | frontend | listen | backend
no | yes | yes | yes
Arguments :
<name> is the name of the filter. Officially supported filters are
referenced in section 9.
<param*> is a list of parameters accepted by the filter <name>. The
parsing of these parameters are the responsibility of the
filter. Please refer to the documentation of the corresponding
filter (section 9) for all details on the supported parameters.
Multiple occurrences of the filter line can be used for the same proxy. The
same filter can be referenced many times if needed.
Example:
listen
bind *:80
filter trace name BEFORE-HTTP-COMP
filter compression
filter trace name AFTER-HTTP-COMP
compression algo gzip
compression offload
server srv1 192.168.0.1:80
See also : section 9.
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
exceptional loads.
Since it's hard to get this value right, haproxy automatically sets it to
10% of the sum of the maxconns of all frontends that may branch to this
backend (based on "use_backend" and "default_backend" rules). That way it's
safe to leave it unset. However, "use_backend" involving dynamic names are
not counted since there is no way to know if they could match or not.
Example :
# 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
yes | 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 equipment 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.
hash-balance-factor <factor>
Specify the balancing factor for bounded-load consistent hashing
May be used in sections : defaults | frontend | listen | backend
yes | no | no | yes
Arguments :
<factor> is the control for the maximum number of concurrent requests to
send to a server, expressed as a percentage of the average number
of concurrent requests across all of the active servers.
Specifying a "hash-balance-factor" for a server with "hash-type consistent"
enables an algorithm that prevents any one server from getting too many
requests at once, even if some hash buckets receive many more requests than
others. Setting <factor> to 0 (the default) disables the feature. Otherwise,
<factor> is a percentage greater than 100. For example, if <factor> is 150,
then no server will be allowed to have a load more than 1.5 times the average.
If server weights are used, they will be respected.
If the first-choice server is disqualified, the algorithm will choose another
server based on the request hash, until a server with additional capacity is
found. A higher <factor> allows more imbalance between the servers, while a
lower <factor> means that more servers will be checked on average, affecting
performance. Reasonable values are from 125 to 200.
This setting is also used by "balance random" which internally relies on the
consistent hashing mechanism.
See also : "balance" and "hash-type".
hash-type <method> <function> <modifier>
Specify a method to use for mapping hashes to servers
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
Arguments :
<method> is the method used to select a server from the hash computed by
the <function> :
map-based the hash table is a static array containing all alive servers.
The hashes will be very smooth, will consider weights, but
will be static in that weight changes while a server is up
will be ignored. This means that there will be no slow start.
Also, since a server is selected by its position in the array,
most mappings are changed when the server count changes. This
means that when a server goes up or down, or when a server is
added to a farm, most connections will be redistributed to
different servers. This can be inconvenient with caches for
instance.
consistent the hash table is a tree filled with many occurrences of each
server. The hash key is looked up in the tree and the closest
server is chosen. This hash is dynamic, it supports changing
weights while the servers are up, so it is compatible with the
slow start feature. It has the advantage that when a server
goes up or down, only its associations are moved. When a
server is added to the farm, only a few part of the mappings
are redistributed, making it an ideal method for caches.
However, due to its principle, the distribution will never be
very smooth and it may sometimes be necessary to adjust a
server's weight or its ID to get a more balanced distribution.
In order to get the same distribution on multiple load
balancers, it is important that all servers have the exact
same IDs. Note: consistent hash uses sdbm and avalanche if no
hash function is specified.
<function> is the hash function to be used :
sdbm this function was created initially for sdbm (a public-domain
reimplementation of ndbm) database library. It was found to do
well in scrambling bits, causing better distribution of the keys
and fewer splits. It also happens to be a good general hashing
function with good distribution, unless the total server weight
is a multiple of 64, in which case applying the avalanche
modifier may help.
djb2 this function was first proposed by Dan Bernstein many years ago
on comp.lang.c. Studies have shown that for certain workload this
function provides a better distribution than sdbm. It generally
works well with text-based inputs though it can perform extremely
poorly with numeric-only input or when the total server weight is
a multiple of 33, unless the avalanche modifier is also used.
wt6 this function was designed for haproxy while testing other
functions in the past. It is not as smooth as the other ones, but
is much less sensible to the input data set or to the number of
servers. It can make sense as an alternative to sdbm+avalanche or
djb2+avalanche for consistent hashing or when hashing on numeric
data such as a source IP address or a visitor identifier in a URL
parameter.
crc32 this is the most common CRC32 implementation as used in Ethernet,
gzip, PNG, etc. It is slower than the other ones but may provide
a better distribution or less predictable results especially when
used on strings.
<modifier> indicates an optional method applied after hashing the key :
avalanche This directive indicates that the result from the hash
function above should not be used in its raw form but that
a 4-byte full avalanche hash must be applied first. The
purpose of this step is to mix the resulting bits from the
previous hash in order to avoid any undesired effect when
the input contains some limited values or when the number of
servers is a multiple of one of the hash's components (64
for SDBM, 33 for DJB2). Enabling avalanche tends to make the
result less predictable, but it's also not as smooth as when
using the original function. Some testing might be needed
with some workloads. This hash is one of the many proposed
by Bob Jenkins.
The default hash type is "map-based" and is recommended for most usages. The
default function is "sdbm", the selection of a function should be based on
the range of the values being hashed.
See also : "balance", "hash-balance-factor", "server"
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