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----------------------
HAProxy
Configuration Manual
----------------------
version 2.4
2022/04/29
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. Conditional blocks
2.5. Time format
2.6. 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
3.8. HTTP-errors
3.9. Rings
3.10. Log forwarding
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
6. Cache
6.1. Limitation
6.2. Setup
6.2.1. Cache section
6.2.2. Proxy 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)
7.3.7. Fetching samples for developers
7.4. Pre-defined ACLs
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
9.6. OpenTracing
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
11. Address formats
11.1. Address family prefixes
11.2. Socket type prefixes
11.3. Protocol prefixes
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.
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").
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. Internally, all header names are
normalized to lower case so that HTTP/1.x and HTTP/2 use the exact same
representation, and they are sent as-is on the other side. This explains why an
HTTP/1.x request typed with camel case is delivered in lower case.
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
404 when the requested resource could not be found
408 when the request timeout strikes before the request is complete
410 when the requested resource is no longer available and will not
be available again
500 when HAProxy encounters an unrecoverable internal error, such as a
memory allocation failure, which should never happen
501 when HAProxy is unable to satisfy a client request because of an
unsupported feature
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 configuration file(s), whose format is described here
- the running process's environment, in case some environment variables are
explicitly referenced
The configuration file follows a fairly simple hierarchical format which obey
a few basic rules:
1. a configuration file is an ordered sequence of statements
2. a statement is a single non-empty line before any unprotected "#" (hash)
3. a line is a series of tokens or "words" delimited by unprotected spaces or
tab characters
4. the first word or sequence of words of a line is one of the keywords or
keyword sequences listed in this document
5. all other words are all arguments of the first one, some being well-known
keywords listed in this document, others being values, references to other
parts of the configuration, or expressions
6. certain keywords delimit a section inside which only a subset of keywords
are supported
7. a section ends at the end of a file or on a special keyword starting a new
section
This is all that is needed to know to write a simple but reliable configuration
generator, but this is not enough to reliably parse any configuration nor to
figure how to deal with certain corner cases.
First, there are a few consequences of the rules above. Rule 6 and 7 imply that
the keywords used to define a new section are valid everywhere and cannot have
a different meaning in a specific section. These keywords are always a single
word (as opposed to a sequence of words), and traditionally the section that
follows them is designated using the same name. For example when speaking about
the "global section", it designates the section of configuration that follows
the "global" keyword. This usage is used a lot in error messages to help locate
the parts that need to be addressed.
A number of sections create an internal object or configuration space, which
requires to be distinguished from other ones. In this case they will take an
extra word which will set the name of this particular section. For some of them
the section name is mandatory. For example "frontend foo" will create a new
section of type "frontend" named "foo". Usually a name is specific to its
section and two sections of different types may use the same name, but this is
not recommended as it tends to complexify configuration management.
A direct consequence of rule 7 is that when multiple files are read at once,
each of them must start with a new section, and the end of each file will end
a section. A file cannot contain sub-sections nor end an existing section and
start a new one.
Rule 1 mentioned that ordering matters. Indeed, some keywords create directives
that can be repeated multiple times to create ordered sequences of rules to be
applied in a certain order. For example "tcp-request" can be used to alternate
"accept" and "reject" rules on varying criteria. As such, a configuration file
processor must always preserve a section's ordering when editing a file. The
ordering of sections usually does not matter except for the global section
which must be placed before other sections, but it may be repeated if needed.
In addition, some automatic identifiers may automatically be assigned to some
of the created objects (e.g. proxies), and by reordering sections, their
identifiers will change. These ones appear in the statistics for example. As
such, the configuration below will assign "foo" ID number 1 and "bar" ID number
2, which will be swapped if the two sections are reversed:
listen foo
bind :80
listen bar
bind :81
Another important point is that according to rules 2 and 3 above, empty lines,
spaces, tabs, and comments following and unprotected "#" character are not part
of the configuration as they are just used as delimiters. This implies that the
following configurations are strictly equivalent:
global#this is the global section
daemon#daemonize
frontend foo
mode http # or tcp
and:
global
daemon
# this is the public web frontend
frontend foo
mode http
The common practice is to align to the left only the keyword that initiates a
new section, and indent (i.e. prepend a tab character or a few spaces) all
other keywords so that it's instantly visible that they belong to the same
section (as done in the second example above). Placing comments before a new
section helps the reader decide if it's the desired one. Leaving a blank line
at the end of a section also visually helps spotting the end when editing it.
Tabs are very convenient for indent but they do not copy-paste well. If spaces
are used instead, it is recommended to avoid placing too many (2 to 4) so that
editing in field doesn't become a burden with limited editors that do not
support automatic indent.
In the early days it used to be common to see arguments split at fixed tab
positions because most keywords would not take more than two arguments. With
modern versions featuring complex expressions this practice does not stand
anymore, and is not recommended.
2.2. Quoting and escaping
-------------------------
In modern configurations, some arguments require the use of some characters
that were previously considered as pure delimiters. In order to make this
possible, HAProxy supports character escaping by prepending a backslash ('\')
in front of the character to be escaped, weak quoting within double quotes
('"') and strong quoting within single quotes ("'").
This is pretty similar to what is done in a number of programming languages and
very close to what is commonly encountered in Bourne shell. The principle is
the following: while the configuration parser cuts the lines into words, it
also takes care of quotes and backslashes to decide whether a character is a
delimiter or is the raw representation of this character within the current
word. The escape character is then removed, the quotes are removed, and the
remaining word is used as-is as a keyword or argument for example.
If a backslash is needed in a word, it must either be escaped using itself
(i.e. double backslash) or be strongly quoted.
Escaping outside quotes 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
In addition, a few non-printable characters may be emitted using their usual
C-language representation:
\n to insert a line feed (LF, character \x0a or ASCII 10 decimal)
\r to insert a carriage return (CR, character \x0d or ASCII 13 decimal)
\t to insert a tab (character \x09 or ASCII 9 decimal)
\xNN to insert character having ASCII code hex NN (e.g \x0a for LF).
Weak quoting is achieved by surrounding double quotes ("") around the character
or sequence of characters to protect. Weak quoting prevents the interpretation
of:
space or tab as a word separator
' single quote as a strong quoting delimiter
# hash as a comment start
Weak quoting permits the interpretation of environment variables (which are not
evaluated outside of quotes) by preceding them with a dollar sign ('$'). If a
dollar character is needed inside double quotes, it must be escaped using a
backslash.
Strong quoting is achieved by surrounding single quotes ('') around the
character or sequence of characters to protect. Inside single quotes, nothing
is interpreted, it's the efficient way to quote regular expressions.
As a result, here is the matrix indicating how special characters can be
entered in different contexts (unprintable characters are replaced with their
name within angle brackets). Note that some characters that may only be
represented escaped have no possible representation inside single quotes,
hence the '-' there:
Character | Unquoted | Weakly quoted | Strongly quoted
-----------+---------------+-----------------------------+-----------------
<TAB> | \<TAB>, \x09 | "<TAB>", "\<TAB>", "\x09" | '<TAB>'
<LF> | \n, \x0a | "\n", "\x0a" | -
<CR> | \r, \x0d | "\r", "\x0d" | -
<SPC> | \<SPC>, \x20 | "<SPC>", "\<SPC>", "\x20" | '<SPC>'
" | \", \x22 | "\"", "\x22" | '"'
# | \#, \x23 | "#", "\#", "\x23" | '#'
$ | $, \$, \x24 | "\$", "\x24" | '$'
' | \', \x27 | "'", "\'", "\x27" | -
\ | \\, \x5c | "\\", "\x5c" | '\'
Example:
# those are all strictly equivalent:
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
There is one particular case where a second level of quoting or escaping may be
necessary. Some keywords take arguments within parenthesis, sometimes delimited
by commas. These arguments are commonly integers or predefined words, but when
they are arbitrary strings, it may be required to perform a separate level of
escaping to disambiguate the characters that belong to the argument from the
characters that are used to delimit the arguments themselves. A pretty common
case is the "regsub" converter. It takes a regular expression in argument, and
if a closing parenthesis is needed inside, this one will require to have its
own quotes.
The keyword argument parser is exactly the same as the top-level one regarding
quotes, except that the \#, \$, and \xNN escapes are not processed. But what is
not always obvious is that the delimiters used inside must first be escaped or
quoted so that they are not resolved at the top level.
Let's take this example making use of the "regsub" converter which takes 3
arguments, one regular expression, one replacement string and one set of flags:
# replace all occurrences of "foo" with "blah" in the path:
http-request set-path %[path,regsub(foo,blah,g)]
Here no special quoting was necessary. But if now we want to replace either
"foo" or "bar" with "blah", we'll need the regular expression "(foo|bar)". We
cannot write:
http-request set-path %[path,regsub((foo|bar),blah,g)]
because we would like the string to cut like this:
http-request set-path %[path,regsub((foo|bar),blah,g)]
|---------|----|-|
arg1 _/ / /
arg2 __________/ /
arg3 ______________/
but actually what is passed is a string between the opening and closing
parenthesis then garbage:
http-request set-path %[path,regsub((foo|bar),blah,g)]
|--------|--------|
arg1=(foo|bar _/ /
trailing garbage _________/
The obvious solution here seems to be that the closing parenthesis needs to be
quoted, but alone this will not work, because as mentioned above, quotes are
processed by the top-level parser which will resolve them before processing
this word:
http-request set-path %[path,regsub("(foo|bar)",blah,g)]
------------ -------- ----------------------------------
word1 word2 word3=%[path,regsub((foo|bar),blah,g)]
So we didn't change anything for the argument parser at the second level which
still sees a truncated regular expression as the only argument, and garbage at
the end of the string. By escaping the quotes they will be passed unmodified to
the second level:
http-request set-path %[path,regsub(\"(foo|bar)\",blah,g)]
------------ -------- ------------------------------------
word1 word2 word3=%[path,regsub("(foo|bar)",blah,g)]
|---------||----|-|
arg1=(foo|bar) _/ / /
arg2=blah ___________/ /
arg3=g _______________/
Another approach consists in using single quotes outside the whole string and
double quotes inside (so that the double quotes are not stripped again):
http-request set-path '%[path,regsub("(foo|bar)",blah,g)]'
------------ -------- ----------------------------------
word1 word2 word3=%[path,regsub("(foo|bar)",blah,g)]
|---------||----|-|
arg1=(foo|bar) _/ / /
arg2 ___________/ /
arg3 _______________/
When using regular expressions, it can happen that the dollar ('$') character
appears in the expression or that a backslash ('\') is used in the replacement
string. In this case these ones will also be processed inside the double quotes
thus single quotes are preferred (or double escaping). Example:
http-request set-path '%[path,regsub("^/(here)(/|$)","my/\1",g)]'
------------ -------- -----------------------------------------
word1 word2 word3=%[path,regsub("^/(here)(/|$)","my/\1",g)]
|-------------| |-----||-|
arg1=(here)(/|$) _/ / /
arg2=my/\1 ________________/ /
arg3 ______________________/
Remember that backslashes are not escape characters within single quotes and
that the whole word above is already protected against them using the single
quotes. Conversely, if double quotes had been used around the whole expression,
single the dollar character and the backslashes would have been resolved at top
level, breaking the argument contents at the second level.
Unfortunately, since single quotes can't be escaped inside of strong quoting,
if you need to include single quotes in your argument, you will need to escape
or quote them twice. There are a few ways to do this:
http-request set-var(txn.foo) str("\\'foo\\'")
http-request set-var(txn.foo) str(\"\'foo\'\")
http-request set-var(txn.foo) str(\\\'foo\\\')
When in doubt, simply do not use quotes anywhere, and start to place single or
double quotes around arguments that require a comma or a closing parenthesis,
and think about escaping these quotes using a backslash if the string contains
a dollar or a backslash. Again, this is pretty similar to what is used under
a Bourne shell when double-escaping a command passed to "eval". For API writers
the best is probably to place escaped quotes around each and every argument,
regardless of their contents. Users will probably find that using single quotes
around the whole expression and double quotes around each argument provides
more readable configurations.
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 ("$") and
optionally enclosed with braces ("{}") similarly to what is done in Bourne
shell. Variable names can contain alphanumerical characters or the character
underscore ("_") but should not start with a digit. If the variable contains a
list of several values separated by spaces, it can be expanded as individual
arguments by enclosing the variable with braces and appending the suffix '[*]'
before the closing brace.
Example:
bind "fd@${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.
In addition, some pseudo-variables are internally resolved and may be used as
regular variables. Pseudo-variables always start with a dot ('.'), and are the
only ones where the dot is permitted. The current list of pseudo-variables is:
* .FILE: the name of the configuration file currently being parsed.
* .LINE: the line number of the configuration file currently being parsed,
starting at one.
* .SECTION: the name of the section currently being parsed, or its type if the
section doesn't have a name (e.g. "global"), or an empty string before the
first section.
These variables are resolved at the location where they are parsed. For example
if a ".LINE" variable is used in a "log-format" directive located in a defaults
section, its line number will be resolved before parsing and compiling the
"log-format" directive, so this same line number will be reused by subsequent
proxies.
This way it is possible to emit information to help locate a rule in variables,
logs, error statuses, health checks, header values, or even to use line numbers
to name some config objects like servers for example.
See also "external-check command" for other variables.
2.4. Conditional blocks
-----------------------
It may sometimes be convenient to be able to conditionally enable or disable
some arbitrary parts of the configuration, for example to enable/disable SSL or
ciphers, enable or disable some pre-production listeners without modifying the
configuration, or adjust the configuration's syntax to support two distinct
versions of HAProxy during a migration.. HAProxy brings a set of nestable
preprocessor-like directives which allow to integrate or ignore some blocks of
text. These directives must be placed on their own line and they act on the
lines that follow them. Two of them support an expression, the other ones only
switch to an alternate block or end a current level. The 4 following directives
are defined to form conditional blocks:
- .if <condition>
- .elif <condition>
- .else
- .endif
The ".if" directive nests a new level, ".elif" stays at the same level, ".else"
as well, and ".endif" closes a level. Each ".if" must be terminated by a
matching ".endif". The ".elif" may only be placed after ".if" or ".elif", and
there is no limit to the number of ".elif" that may be chained. There may be
only one ".else" per ".if" and it must always be after the ".if" or the last
".elif" of a block.
Comments may be placed on the same line if needed after a '#', they will be
ignored. The directives are tokenized like other configuration directives, and
as such it is possible to use environment variables in conditions.
The conditions are currently limited to:
- an empty string, always returns "false"
- the integer zero ('0'), always returns "false"
- a non-nul integer (e.g. '1'), always returns "true".
- a predicate optionally followed by argument(s) in parenthesis.
The list of currently supported predicates is the following:
- defined(<name>) : returns true if an environment variable <name>
exists, regardless of its contents
- feature(<name>) : returns true if feature <name> is listed as present
in the features list reported by "haproxy -vv"
(which means a <name> appears after a '+')
- streq(<str1>,<str2>) : returns true only if the two strings are equal
- strneq(<str1>,<str2>) : returns true only if the two strings differ
- version_atleast(<ver>): returns true if the current haproxy version is
at least as recent as <ver> otherwise false. The
version syntax is the same as shown by "haproxy -v"
and missing components are assumed as being zero.
- version_before(<ver>) : returns true if the current haproxy version is
strictly older than <ver> otherwise false. The
version syntax is the same as shown by "haproxy -v"
and missing components are assumed as being zero.
Example:
.if defined(HAPROXY_MWORKER)
listen mwcli_px
bind :1111
...
.endif
.if strneq("$SSL_ONLY",yes)
bind :80
.endif
.if streq("$WITH_SSL",yes)
.if feature(OPENSSL)
bind :443 ssl crt ...
.endif
.endif
.if version_atleast(2.4-dev19)
profiling.memory on
.endif
Four other directives are provided to report some status:
- .diag "message" : emit this message only when in diagnostic mode (-dD)
- .notice "message" : emit this message at level NOTICE
- .warning "message" : emit this message at level WARNING
- .alert "message" : emit this message at level ALERT
Messages emitted at level WARNING may cause the process to fail to start if the
"strict-mode" is enabled. Messages emitted at level ALERT will always cause a
fatal error. These can be used to detect some inappropriate conditions and
provide advice to the user.
Example:
.if "${A}"
.if "${B}"
.notice "A=1, B=1"
.elif "${C}"
.notice "A=1, B=0, C=1"
.elif "${D}"
.warning "A=1, B=0, C=0, D=1"
.else
.alert "A=1, B=0, C=0, D=0"
.endif
.else
.notice "A=0"
.endif
.diag "WTA/2021-05-07: replace 'redirect' with 'return' after switch to 2.4"
http-request redirect location /goaway if ABUSE
2.5. 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
2.6. 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
- default-path
- description
- deviceatlas-json-file
- deviceatlas-log-level
- deviceatlas-separator
- deviceatlas-properties-cookie
- expose-experimental-directives
- external-check
- gid
- group
- hard-stop-after
- h1-case-adjust
- h1-case-adjust-file
- insecure-fork-wanted
- insecure-setuid-wanted
- issuers-chain-path
- h2-workaround-bogus-websocket-clients
- localpeer
- log
- log-tag
- log-send-hostname
- lua-load
- lua-load-per-thread
- lua-prepend-path
- mworker-max-reloads
- nbproc
- nbthread
- node
- numa-cpu-mapping
- pidfile
- pp2-never-send-local
- presetenv
- resetenv
- uid
- ulimit-n
- user
- set-dumpable
- set-var
- setenv
- stats
- ssl-default-bind-ciphers
- ssl-default-bind-ciphersuites
- ssl-default-bind-curves
- ssl-default-bind-options
- ssl-default-server-ciphers
- ssl-default-server-ciphersuites
- ssl-default-server-options
- ssl-dh-param-file
- ssl-server-verify
- ssl-skip-self-issued-ca
- 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
- no-memory-trimming
- 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.fd.edge-triggered
- 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.idle-pool.shared
- 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.pool-high-fd-ratio
- tune.pool-low-fd-ratio
- tune.rcvbuf.client
- tune.rcvbuf.server
- tune.recv_enough
- tune.runqueue-depth
- tune.sched.low-latency
- tune.sndbuf.client
- tune.sndbuf.server
- tune.ssl.cachesize
- tune.ssl.keylog
- 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
- quiet
- zero-warning
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", "ca-verify-file" or "crl-file"
directives. Absolute locations specified in "ca-file", "ca-verify-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 starting at 0 for the first
CPU or a range with two such numbers delimited by a dash ('-'). Outside of
Linux and BSDs, there may be a limitation on the maximum CPU index to either
31 or 63. 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" or "crt" directives. Absolute locations specified
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.
default-path { current | config | parent | origin <path> }
By default HAProxy loads all files designated by a relative path from the
location the process is started in. In some circumstances it might be
desirable to force all relative paths to start from a different location
just as if the process was started from such locations. This is what this
directive is made for. Technically it will perform a temporary chdir() to
the designated location while processing each configuration file, and will
return to the original directory after processing each file. It takes an
argument indicating the policy to use when loading files whose path does
not start with a slash ('/'):
- "current" indicates that all relative files are to be loaded from the
directory the process is started in ; this is the default.
- "config" indicates that all relative files should be loaded from the
directory containing the configuration file. More specifically, if the
configuration file contains a slash ('/'), the longest part up to the
last slash is used as the directory to change to, otherwise the current
directory is used. This mode is convenient to bundle maps, errorfiles,
certificates and Lua scripts together as relocatable packages. When
multiple configuration files are loaded, the directory is updated for
each of them.
- "parent" indicates that all relative files should be loaded from the
parent of the directory containing the configuration file. More
specifically, if the configuration file contains a slash ('/'), ".."
is appended to the longest part up to the last slash is used as the
directory to change to, otherwise the directory is "..". This mode is
convenient to bundle maps, errorfiles, certificates and Lua scripts
together as relocatable packages, but where each part is located in a
different subdirectory (e.g. "config/", "certs/", "maps/", ...).
- "origin" indicates that all relative files should be loaded from the
designated (mandatory) path. This may be used to ease management of
different HAProxy instances running in parallel on a system, where each
instance uses a different prefix but where the rest of the sections are
made easily relocatable.
Each "default-path" directive instantly replaces any previous one and will
possibly result in switching to a different directory. While this should
always result in the desired behavior, it is really not a good practice to
use multiple default-path directives, and if used, the policy ought to remain
consistent across all configuration files.
Warning: some configuration elements such as maps or certificates are
uniquely identified by their configured path. By using a relocatable layout,
it becomes possible for several of them to end up with the same unique name,
making it difficult to update them at run time, especially when multiple
configuration files are loaded from different directories. It is essential to
observe a strict collision-free file naming scheme before adopting relative
paths. A robust approach could consist in prefixing all files names with
their respective site name, or in doing so at the directory level.
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.
expose-experimental-directives
This statement must appear before using directives tagged as experimental or
the config file will be rejected.
external-check
Allows the use of an external agent to perform health checks. This is
disabled by default as a security precaution, and even when enabled, checks
may still fail unless "insecure-fork-wanted" is enabled as well. If the
program launched makes use of a setuid executable (it should really not),
you may also need to set "insecure-setuid-wanted" in the global section.
See "option external-check", and "insecure-fork-wanted", and
"insecure-setuid-wanted".
gid <number>
Changes the process's 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".
group <group name>
Similar to "gid" but uses the GID of group name <group name> from /etc/group.
See also "gid" and "user".
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
adjusted. 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".
insecure-fork-wanted
By default HAProxy tries hard to prevent any thread and process creation
after it starts. Doing so is particularly important when using Lua files of
uncertain origin, and when experimenting with development versions which may
still contain bugs whose exploitability is uncertain. And generally speaking
it's good hygiene to make sure that no unexpected background activity can be
triggered by traffic. But this prevents external checks from working, and may
break some very specific Lua scripts which actively rely on the ability to
fork. This option is there to disable this protection. Note that it is a bad
idea to disable it, as a vulnerability in a library or within HAProxy itself
will be easier to exploit once disabled. In addition, forking from Lua or
anywhere else is not reliable as the forked process may randomly embed a lock
set by another thread and never manage to finish an operation. As such it is
highly recommended that this option is never used and that any workload
requiring such a fork be reconsidered and moved to a safer solution (such as
agents instead of external checks). This option supports the "no" prefix to
disable it.
insecure-setuid-wanted
HAProxy doesn't need to call executables at run time (except when using
external checks which are strongly recommended against), and is even expected
to isolate itself into an empty chroot. As such, there basically is no valid
reason to allow a setuid executable to be called without the user being fully
aware of the risks. In a situation where HAProxy would need to call external
checks and/or disable chroot, exploiting a vulnerability in a library or in
HAProxy itself could lead to the execution of an external program. On Linux
it is possible to lock the process so that any setuid bit present on such an
executable is ignored. This significantly reduces the risk of privilege
escalation in such a situation. This is what HAProxy does by default. In case
this causes a problem to an external check (for example one which would need
the "ping" command), then it is possible to disable this protection by
explicitly adding this directive in the global section. If enabled, it is
possible to turn it back off by prefixing it with the "no" keyword.
issuers-chain-path <dir>
Assigns a directory to load certificate chain for issuer completion. All
files must be in PEM format. For certificates loaded with "crt" or "crt-list",
if certificate chain is not included in PEM (also commonly known as
intermediate certificate), HAProxy will complete chain if the issuer of the
certificate corresponds to the first certificate of the chain loaded with
"issuers-chain-path".
A "crt" file with PrivateKey+Certificate+IntermediateCA2+IntermediateCA1
could be replaced with PrivateKey+Certificate. HAProxy will complete the
chain if a file with IntermediateCA2+IntermediateCA1 is present in
"issuers-chain-path" directory. All other certificates with the same issuer
will share the chain in memory.
h2-workaround-bogus-websocket-clients
This disables the announcement of the support for h2 websockets to clients.
This can be use to overcome clients which have issues when implementing the
relatively fresh RFC8441, such as Firefox 88. To allow clients to
automatically downgrade to http/1.1 for the websocket tunnel, specify h2
support on the bind line using "alpn" without an explicit "proto" keyword. If
this statement was previously activated, this can be disabled by prefixing
the keyword with "no'.
localpeer <name>
Sets the local instance's peer name. It will be ignored if the "-L"
command line argument is specified or if used after "peers" section
definitions. In such cases, a warning message will be emitted during
the configuration parsing.
This option will also set the HAPROXY_LOCALPEER environment variable.
See also "-L" in the management guide and "peers" section below.
log <address> [len <length>] [format <format>] [sample <ranges>:<sample_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 :
local Analog to rfc3164 syslog message format except that hostname
field is stripped. This is the default.
Note: option "log-send-hostname" switches the default to
rfc3164.
rfc3164 The RFC3164 syslog message format.
(https://tools.ietf.org/html/rfc3164)
rfc5424 The RFC5424 syslog message format.
(https://tools.ietf.org/html/rfc5424)
priority A message containing only a level plus syslog facility between
angle brackets such as '<63>', followed by the text. The PID,
date, time, process name and system name are omitted. This is
designed to be used with a local log server.
short A message containing only a level between angle brackets such as
'<3>', followed by the text. The PID, date, time, process name
and system name are omitted. This is designed to be used with a
local log server. This format is compatible with what the systemd
logger consumes.
timed A message containing only a level between angle brackets such as
'<3>', followed by ISO date and by the text. The PID, process
name and system name are omitted. This is designed to be
used with a local log server.
iso A message containing only the ISO date, followed by the text.
The PID, process name and system name are omitted. This is
designed to be used with a local log server.
raw A message containing only the text. The level, PID, date, time,
process name and system name are omitted. This is designed to be
used in containers or during development, where the severity only
depends on the file descriptor used (stdout/stderr).
<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 in the shared context
that is visible to all threads. Any variable set in such a context is visible
from any thread. This is the easiest and recommended way to load Lua programs
but it will not scale well if a lot of Lua calls are performed, as only one
thread may be running on the global state at a time. A program loaded this
way will always see 0 in the "core.thread" variable. This directive can be
used multiple times.
lua-load-per-thread <file>
This global directive loads and executes a Lua file into each started thread.
Any global variable has a thread-local visibility so that each thread could
see a different value. As such it is strongly recommended not to use global
variables in programs loaded this way. An independent copy is loaded and
initialized for each thread, everything is done sequentially and in the
thread's numeric order from 1 to nbthread. If some operations need to be
performed only once, the program should check the "core.thread" variable to
figure what thread is being initialized. Programs loaded this way will run
concurrently on all threads and will be highly scalable. This is the
recommended way to load simple functions that register sample-fetches,
converters, actions or services once it is certain the program doesn't depend
on global variables. For the sake of simplicity, the directive is available
even if only one thread is used and even if threads are disabled (in which
case it will be equivalent to lua-load). This directive can be used multiple
times.
lua-prepend-path <string> [<type>]
Prepends the given string followed by a semicolon to Lua's package.<type>
variable.
<type> must either be "path" or "cpath". If <type> is not given it defaults
to "path".
Lua's paths are semicolon delimited lists of patterns that specify how the
`require` function attempts to find the source file of a library. Question
marks (?) within a pattern will be replaced by module name. The path is
evaluated left to right. This implies that paths that are prepended later
will be checked earlier.
As an example by specifying the following path:
lua-prepend-path /usr/share/haproxy-lua/?/init.lua
lua-prepend-path /usr/share/haproxy-lua/?.lua
When `require "example"` is being called Lua will first attempt to load the
/usr/share/haproxy-lua/example.lua script, if that does not exist the
/usr/share/haproxy-lua/example/init.lua will be attempted and the default
paths if that does not exist either.
See https://www.lua.org/pil/8.1.html for the details within the Lua
documentation.
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> (deprecated)
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. This directive is deprecated
and scheduled for removal in 2.5. Please use "nbthread" instead. 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".
numa-cpu-mapping
By default, if running on Linux, HAProxy inspects on startup the CPU topology
of the machine. If a multi-socket machine is detected, the affinity is
automatically calculated to run on the CPUs of a single node. This is done in
order to not suffer from the performance penalties caused by the inter-socket
bus latency. However, if the applied binding is non optimal on a particular
architecture, it can be disabled with the statement 'no numa-cpu-mapping'.
This automatic binding is also not applied if a nbthread statement is present
in the configuration, or the affinity of the process is already specified,
for example via the 'cpu-map' directive or the taskset utility.
pidfile <pidfile>
Writes PIDs of all daemons into file <pidfile> when daemon mode or writes PID
of master process into file <pidfile> when master-worker mode. This option is
equivalent to the "-p" command line argument. The file must be accessible to
the user starting the process. See also "daemon" and "master-worker".
pp2-never-send-local
A bug in the PROXY protocol v2 implementation was present in HAProxy up to
version 2.1, causing it to emit a PROXY command instead of a LOCAL command
for health checks. This is particularly minor but confuses some servers'
logs. Sadly, the bug was discovered very late and revealed that some servers
which possibly only tested their PROXY protocol implementation against
HAProxy fail to properly handle the LOCAL command, and permanently remain in
the "down" state when HAProxy checks them. When this happens, it is possible
to enable this global option to revert to the older (bogus) behavior for the
time it takes to contact the affected components' vendors and get them fixed.
This option is disabled by default and acts on all servers having the
"send-proxy-v2" statement.
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"
set-var <var-name> <expr>
Sets the process-wide variable '<var-name>' to the result of the evaluation
of the sample expression <expr>. The variable '<var-name>' may only be a
process-wide variable (using the 'proc.' prefix). It works exactly like the
'set-var' action in TCP or HTTP rules except that the expression is evaluated
at configuration parsing time and that the variable is instantly set. The
sample fetch functions and converters permitted in the expression are only
those using internal data, typically 'int(value)' or 'str(value)'. It's is
possible to reference previously allocated variables as well. These variables
will then be readable (and modifiable) from the regular rule sets.
Example:
global
set-var proc.current_state str(primary)
set-var proc.prio int(100)
set-var proc.threshold int(200),sub(proc.prio)
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-curves <curves>
This setting is only available when support for OpenSSL was built in. It sets
the default string describing the list of elliptic curves algorithms ("curve
suite") that are negotiated during the SSL/TLS handshake with ECDHE. The format
of the string is a colon-delimited list of curve name.
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-load-extra-del-ext
This setting allows to configure the way HAProxy does the lookup for the
extra SSL files. By default HAProxy adds a new extension to the filename.
(ex: with "foobar.crt" load "foobar.crt.key"). With this option enabled,
HAProxy removes the extension before adding the new one (ex: with
"foobar.crt" load "foobar.key").
Your crt file must have a ".crt" extension for this option to work.
This option is not compatible with bundle extensions (.ecdsa, .rsa. .dsa)
and won't try to remove them.
This option is disabled by default. See also "ssl-load-extra-files".
ssl-load-extra-files <none|all|bundle|sctl|ocsp|issuer|key>*
This setting alters the way HAProxy will look for unspecified files during
the loading of the SSL certificates. This option applies to certificates
associated to "bind" lines as well as "server" lines but some of the extra
files will not have any functional impact for "server" line certificates.
By default, HAProxy discovers automatically a lot of files not specified in
the configuration, and you may want to disable this behavior if you want to
optimize the startup time.
"none": Only load the files specified in the configuration. Don't try to load
a certificate bundle if the file does not exist. In the case of a directory,
it won't try to bundle the certificates if they have the same basename.
"all": This is the default behavior, it will try to load everything,
bundles, sctl, ocsp, issuer, key.
"bundle": When a file specified in the configuration does not exist, HAProxy
will try to load a "cert bundle". Certificate bundles are only managed on the
frontend side and will not work for backend certificates.
Starting from HAProxy 2.3, the bundles are not loaded in the same OpenSSL
certificate store, instead it will loads each certificate in a separate
store which is equivalent to declaring multiple "crt". OpenSSL 1.1.1 is
required to achieve this. Which means that bundles are now used only for
backward compatibility and are not mandatory anymore to do an hybrid RSA/ECC
bind configuration.
To associate these PEM files into a "cert bundle" that is recognized by
HAProxy, they must be named in the following way: All PEM files that are to
be bundled must have the same base name, with a suffix indicating the key
type. Currently, three suffixes are supported: rsa, dsa and ecdsa. For
example, if www.example.com has two PEM files, an RSA file and an ECDSA
file, they must be named: "example.pem.rsa" and "example.pem.ecdsa". The
first part of the filename is arbitrary; only the suffix matters. To load
this bundle into HAProxy, specify the base name only:
Example : bind :8443 ssl crt example.pem
Note that the suffix is not given to HAProxy; this tells HAProxy to look for
a cert bundle.
HAProxy will load all PEM files in the bundle as if they were configured
separately in several "crt".
The bundle loading does not have an impact anymore on the directory loading
since files are loading separately.
On the CLI, bundles are seen as separate files, and the bundle extension is
required to commit them.
OCSP files (.ocsp), issuer files (.issuer), Certificate Transparency (.sctl)
as well as private keys (.key) are supported with multi-cert bundling.
"sctl": Try to load "<basename>.sctl" for each crt keyword. If provided for
a backend certificate, it will be loaded but will not have any functional
impact.
"ocsp": Try to load "<basename>.ocsp" for each crt keyword. If provided for
a backend certificate, it will be loaded but will not have any functional
impact.
"issuer": Try to load "<basename>.issuer" if the issuer of the OCSP file is
not provided in the PEM file. If provided for a backend certificate, it will
be loaded but will not have any functional impact.
"key": If the private key was not provided by the PEM file, try to load a
file "<basename>.key" containing a private key.
The default behavior is "all".
Example:
ssl-load-extra-files bundle sctl
ssl-load-extra-files sctl ocsp issuer
ssl-load-extra-files none
See also: "crt", section 5.1 about bind options and section 5.2 about server
options.
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'.
ssl-skip-self-issued-ca
Self issued CA, aka x509 root CA, is the anchor for chain validation: as a
server is useless to send it, client must have it. Standard configuration
need to not include such CA in PEM file. This option allows you to keep such
CA in PEM file without sending it to the client. Use case is to provide
issuer for ocsp without the need for '.issuer' file and be able to share it
with 'issuers-chain-path'. This concerns all certificates without intermediate
certificates. It's useless for BoringSSL, .issuer is ignored because ocsp
bits does not need it. Requires at least OpenSSL 1.0.2.
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's 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 tries to set the
best setrlimit according to what has been calculated. If it fails, it will
emit a warning. This option is here to guarantee an explicit failure of
HAProxy when those limits fail. It is enabled by default. 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.
This option is automatically disabled on old processes in the context of
seamless reload; it avoids too much cpu conflicts when multiple processes
stay around for some time waiting for the end of their current connections.
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.
no-memory-trimming
Disables memory trimming ("malloc_trim") at a few moments where attempts are
made to reclaim lots of memory (on memory shortage or on reload). Trimming
memory forces the system's allocator to scan all unused areas and to release
them. This is generally seen as nice action to leave more available memory to
a new process while the old one is unlikely to make significant use of it.
But some systems dealing with tens to hundreds of thousands of concurrent
connections may experience a lot of memory fragmentation, that may render
this release operation extremely long. During this time, no more traffic
passes through the process, new connections are not accepted anymore, some
health checks may even fail, and the watchdog may even trigger and kill the
unresponsive process, leaving a huge core dump. If this ever happens, then it
is suggested to use this option to disable trimming and stop trying to be
nice with the new process. Note that advanced memory allocators usually do
not suffer from such a problem.
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.memory { on | off }
Enables ('on') or disables ('off') per-function memory profiling. This will
keep usage statistics of malloc/calloc/realloc/free calls anywhere in the
process (including libraries) which will be reported on the CLI using the
"show profiling" command. This is essentially meant to be used when an
abnormal memory usage is observed that cannot be explained by the pools and
other info are required. The performance hit will typically be around 1%,
maybe a bit more on highly threaded machines, so it is normally suitable for
use in production. The same may be achieved at run time on the CLI using the
"set profiling memory" command, please consult the management manual.
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> (deprecated)
This option is deprecated and ignored.
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.fd.edge-triggered { on | off } [ EXPERIMENTAL ]
Enables ('on') or disables ('off') the edge-triggered polling mode for FDs
that support it. This is currently only support with epoll. It may noticeably
reduce the number of epoll_ctl() calls and slightly improve performance in
certain scenarios. This is still experimental, it may result in frozen
connections if bugs are still present, and is disabled by default.
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.idle-pool.shared { on | off }
Enables ('on') or disables ('off') sharing of idle connection pools between
threads for a same server. The default is to share them between threads in
order to minimize the number of persistent connections to a server, and to
optimize the connection reuse rate. But to help with debugging or when
suspecting a bug in HAProxy around connection reuse, it can be convenient to
forcefully disable this idle pool sharing between multiple threads, and force
this option to "off". The default is on. It is strongly recommended against
disabling this option without setting a conservative value on "pool-low-conn"
for all servers relying on connection reuse to achieve a high performance
level, otherwise connections might be closed very often as the thread count
increases.
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
used to give better performance at high connection rates, though this is not
the case anymore with the multi-queue. This value applies individually to
each listener, so that the number of processes a listener is bound to is
taken into account. This value defaults to 4 which showed best results. If a
significantly higher value was inherited from an ancient config, it might be
worth removing it as it will both increase performance and lower response
time. In multi-process mode, it is divided by twice the number of processes
the listener is bound to. Setting this value to -1 completely disables the
limitation. It should normally not be needed to tweak this value.
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-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.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.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 depends on the number of threads but sits between 35
and 280, which tend to show the highest request rates and lowest latencies.
Increasing it may incur latency when dealing with I/Os, making it too small
can incur extra overhead. Higher thread counts benefit from lower values.
When experimenting with much larger values, it may be useful to also enable
tune.sched.low-latency and possibly tune.fd.edge-triggered to limit the
maximum latency to the lowest possible.
tune.sched.low-latency { on | off }
Enables ('on') or disables ('off') the low-latency task scheduler. By default
HAProxy processes tasks from several classes one class at a time as this is
the most efficient. But when running with large values of tune.runqueue-depth
this can have a measurable effect on request or connection latency. When this
low-latency setting is enabled, tasks of lower priority classes will always
be executed before other ones if they exist. This will permit to lower the
maximum latency experienced by new requests or connections in the middle of
massive traffic, at the expense of a higher impact on this large traffic.
For regular usage it is better to leave this off. The default value is off.
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 (based on `sizeof(struct sh_ssl_sess_hdr) + SHSESS_BLOCK_MIN_SIZE`
calculation used for `shctx_init` function). The default value may be forced
at build time, otherwise defaults to 20000. When the cache is full, the most
idle entries are purged and reassigned. Higher values reduce the occurrence
of such a purge, hence the number of CPU-intensive SSL handshakes by ensuring
that all users keep their session as long as possible. All entries are
pre-allocated upon startup 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.keylog { on | off }
This option activates the logging of the TLS keys. It should be used with
care as it will consume more memory per SSL session and could decrease
performances. This is disabled by default.
These sample fetches should be used to generate the SSLKEYLOGFILE that is
required to decipher traffic with wireshark.
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/Key_Log_Format
The SSLKEYLOG is a series of lines which are formatted this way:
<Label> <space> <ClientRandom> <space> <Secret>
The ClientRandom is provided by the %[ssl_fc_client_random,hex] sample
fetch, the secret and the Label could be find in the array below. You need
to generate a SSLKEYLOGFILE with all the labels in this array.
The following sample fetches are hexadecimal strings and does not need to be
converted.
SSLKEYLOGFILE Label | Sample fetches for the Secrets
--------------------------------|-----------------------------------------
CLIENT_EARLY_TRAFFIC_SECRET | %[ssl_fc_client_early_traffic_secret]
CLIENT_HANDSHAKE_TRAFFIC_SECRET | %[ssl_fc_client_handshake_traffic_secret]
SERVER_HANDSHAKE_TRAFFIC_SECRET | %[ssl_fc_server_handshake_traffic_secret]
CLIENT_TRAFFIC_SECRET_0 | %[ssl_fc_client_traffic_secret_0]
SERVER_TRAFFIC_SECRET_0 | %[ssl_fc_server_traffic_secret_0]
EXPORTER_SECRET | %[ssl_fc_exporter_secret]
EARLY_EXPORTER_SECRET | %[ssl_fc_early_exporter_secret]
This is only available with OpenSSL 1.1.1, and useful with TLS1.3 session.
If you want to generate the content of a SSLKEYLOGFILE with TLS < 1.3, you
only need this line:
"CLIENT_RANDOM %[ssl_fc_client_random,hex] %[ssl_fc_session_key,hex]"
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 2048. 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
--------------
quiet
Do not display any message during startup. It is equivalent to the command-
line argument "-q".
zero-warning
When this option is set, HAProxy will refuse to start if any warning was
emitted while processing the configuration. It is highly recommended to set
this option on configurations that are not changed often, as it helps detect
subtle mistakes and keep the configuration clean and forward-compatible. Note
that "haproxy -c" will also report errors in such a case. This option is
equivalent to command line argument "-dW".
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
enabled
This re-enables a peers section which was previously disabled via the
"disabled" keyword.
log <address> [len <length>] [format <format>] [sample <ranges>:<sample_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 or "localpeer" global configuration setting),
HAProxy will listen for incoming remote peer connection on <ip>:<port>.
Otherwise, <ip>:<port> defines where to connect to in order 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 or the "localpeer"
global configuration setting 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 "mypeers" 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.
3.8. HTTP-errors
----------------
It is possible to globally declare several groups of HTTP errors, to be
imported afterwards in any proxy section. Same group may be referenced at
several places and can be fully or partially imported.
http-errors <name>
Create a new http-errors group with the name <name>. It is an independent
section that may be referenced by one or more proxies using its name.
errorfile <code> <file>
Associate a file contents to an HTTP error code
Arguments :
<code> is the HTTP status code. Currently, HAProxy is capable of
generating codes 200, 400, 401, 403, 404, 405, 407, 408, 410,
425, 429, 500, 501, 502, 503, and 504.
<file> designates a file containing the full HTTP response. It is
recommended to follow the common practice of appending ".http" to
the filename so that people do not confuse the response with HTML
error pages, and to use absolute paths, since files are read
before any chroot is performed.
Please referrers to "errorfile" keyword in section 4 for details.
Example:
http-errors website-1
errorfile 400 /etc/haproxy/errorfiles/site1/400.http
errorfile 404 /etc/haproxy/errorfiles/site1/404.http
errorfile 408 /dev/null # work around Chrome pre-connect bug
http-errors website-2
errorfile 400 /etc/haproxy/errorfiles/site2/400.http
errorfile 404 /etc/haproxy/errorfiles/site2/404.http
errorfile 408 /dev/null # work around Chrome pre-connect bug
3.9. Rings
----------
It is possible to globally declare ring-buffers, to be used as target for log
servers or traces.
ring <ringname>
Creates a new ring-buffer with name <ringname>.
description <text>
The description is an optional description string of the ring. It will
appear on CLI. By default, <name> is reused to fill this field.
format <format>
Format used to store events into the ring buffer.
Arguments:
<format> is the log format used when generating syslog messages. It may be
one of the following :
iso A message containing only the ISO date, followed by the text.
The PID, process name and system name are omitted. This is
designed to be used with a local log server.
local Analog to rfc3164 syslog message format except that hostname
field is stripped. This is the default.
Note: option "log-send-hostname" switches the default to
rfc3164.
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). This
is the default.
rfc3164 The RFC3164 syslog message format.
(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.
priority A message containing only a level plus syslog facility between angle
brackets such as '<63>', followed by the text. The PID, date, time,
process name and system name are omitted. This is designed to be used
with a local log server.
timed A message containing only a level between angle brackets such as
'<3>', followed by ISO date and by the text. The PID, process
name and system name are omitted. This is designed to be
used with a local log server.
maxlen <length>
The maximum length of an event message stored into the ring,
including formatted header. If an event message is longer than
<length>, it will be truncated to this length.
server <name> <address> [param*]
Used to configure a syslog tcp server to forward messages from ring buffer.
This supports for all "server" parameters found in 5.2 paragraph. Some of
these parameters are irrelevant for "ring" sections. Important point: there
is little reason to add more than one server to a ring, because all servers
will receive the exact same copy of the ring contents, and as such the ring
will progress at the speed of the slowest server. If one server does not
respond, it will prevent old messages from being purged and may block new
messages from being inserted into the ring. The proper way to send messages
to multiple servers is to use one distinct ring per log server, not to
attach multiple servers to the same ring. Note that specific server directive
"log-proto" is used to set the protocol used to send messages.
size <size>
This is the optional size in bytes for the ring-buffer. Default value is
set to BUFSIZE.
timeout connect <timeout>
Set the maximum time to wait for a connection attempt to a server to succeed.
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
timeout server <timeout>
Set the maximum time for pending data staying into output buffer.
Arguments :
<timeout> is the timeout value specified in milliseconds by default, but
can be in any other unit if the number is suffixed by the unit,
as explained at the top of this document.
Example:
global
log ring@myring local7
ring myring
description "My local buffer"
format rfc3164
maxlen 1200
size 32764
timeout connect 5s
timeout server 10s
server mysyslogsrv 127.0.0.1:6514 log-proto octet-count
3.10. Log forwarding
-------------------
It is possible to declare one or multiple log forwarding section,
HAProxy will forward all received log messages to a log servers list.
log-forward <name>
Creates a new log forwarder proxy identified as <name>.
backlog <conns>
Give hints to the system about the approximate listen backlog desired size
on connections accept.
bind <addr> [param*]
Used to configure a stream log listener to receive messages to forward.
This supports the "bind" parameters found in 5.1 paragraph including
those about ssl but some statements such as "alpn" may be irrelevant for
syslog protocol over TCP.
Those listeners support both "Octet Counting" and "Non-Transparent-Framing"
modes as defined in rfc-6587.
dgram-bind <addr> [param*]
Used to configure a datagram log listener to receive messages to forward.
Addresses must be in IPv4 or IPv6 form,followed by a port. This supports
for some of the "bind" parameters found in 5.1 paragraph among which
"interface", "namespace" or "transparent", the other ones being
silently ignored as irrelevant for UDP/syslog case.
log global
log <address> [len <length>] [format <format>] [sample <ranges>:<sample_size>]
<facility> [<level> [<minlevel>]]
Used to configure target log servers. See more details on proxies
documentation.
If no format specified, HAProxy tries to keep the incoming log format.
Configured facility is ignored, except if incoming message does not
present a facility but one is mandatory on the outgoing format.
If there is no timestamp available in the input format, but the field
exists in output format, HAProxy will use the local date.
Example:
global
log stderr format iso local7
ring myring
description "My local buffer"
format rfc5424
maxlen 1200
size 32764
timeout connect 5s
timeout server 10s
# syslog tcp server
server mysyslogsrv 127.0.0.1:514 log-proto octet-count
log-forward sylog-loadb
dgram-bind 127.0.0.1:1514
bind 127.0.0.1:1514
# all messages on stderr
log global
# all messages on local tcp syslog server
log ring@myring local0
# load balance messages on 4 udp syslog servers
log 127.0.0.1:10001 sample 1:4 local0
log 127.0.0.1:10002 sample 2:4 local0
log 127.0.0.1:10003 sample 3:4 local0
log 127.0.0.1:10004 sample 4:4 local0
maxconn <conns>
Fix the maximum number of concurrent connections on a log forwarder.
10 is the default.
timeout client <timeout>
Set the maximum inactivity time on the client side.
4. Proxies
----------
Proxy configuration can be located in a set of sections :
- defaults [<name>] [ from <defaults_name> ]
- frontend <name> [ from <defaults_name> ]
- backend <name> [ from <defaults_name> ]
- listen <name> [ from <defaults_name> ]
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.
A "defaults" section resets all settings to the documented ones and presets new
ones for use by subsequent sections. All of "frontend", "backend" and "listen"
sections always take their initial settings from a defaults section, by default
the latest one that appears before the newly created section. It is possible to
explicitly designate a specific "defaults" section to load the initial settings
from by indicating its name on the section line after the optional keyword
"from". While "defaults" section do not impose a name, this use is encouraged
for better readability. It is also the only way to designate a specific section
to use instead of the default previous one. Since "defaults" section names are
optional, by default a very permissive check is applied on their name and these
are even permitted to overlap. However if a "defaults" section is referenced by
any other section, its name must comply with the syntax imposed on all proxy
names, and this name must be unique among the defaults sections. Please note
that regardless of what is currently permitted, it is recommended to avoid
duplicate section names in general and to respect the same syntax as for proxy
names. This rule might be enforced in a future version.
Note that it is even possible for a defaults section to take its initial
settings from another one, and as such, inherit settings across multiple levels
of defaults sections. This can be convenient to establish certain configuration
profiles to carry groups of default settings (e.g. TCP vs HTTP or short vs long
timeouts) but can quickly become confusing to follow.
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 3 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
It is possible to chain a TCP frontend to an HTTP backend. It is pointless if
only HTTP traffic is handled. But it may be used to handle several protocols
within the same frontend. In this case, the client's connection is first handled
as a raw tcp connection before being upgraded to HTTP. Before the upgrade, the
content processings are performend on raw data. Once upgraded, data is parsed
and stored using an internal representation called HTX and it is no longer
possible to rely on raw representation. There is no way to go back.
There are two kind of upgrades, in-place upgrades and destructive upgrades. The
first ones involves a TCP to HTTP/1 upgrade. In HTTP/1, the request
processings are serialized, thus the applicative stream can be preserved. The
second one involves a TCP to HTTP/2 upgrade. Because it is a multiplexed
protocol, the applicative stream cannot be associated to any HTTP/2 stream and
is destroyed. New applicative streams are then created when HAProxy receives
new HTTP/2 streams at the lower level, in the H2 multiplexer. It is important
to understand this difference because that drastically changes the way to
process data. When an HTTP/1 upgrade is performed, the content processings
already performed on raw data are neither lost nor reexecuted while for an
HTTP/2 upgrade, applicative streams are distinct and all frontend rules are
evaluated systematically on each one. And as said, the first stream, the TCP
one, is destroyed, but only after the frontend rules were evaluated.
There is another importnat point to understand when HTTP processings are
performed from a TCP proxy. While HAProxy is able to parse HTTP/1 in-fly from
tcp-request content rules, it is not possible for HTTP/2. Only the HTTP/2
preface can be parsed. This is a huge limitation regarding the HTTP content
analysis in TCP. Concretely it is only possible to know if received data are
HTTP. For instance, it is not possible to choose a backend based on the Host
header value while it is trivial in HTTP/1. Hopefully, there is a solution to
mitigate this drawback.
There are two ways to perform an HTTP upgrade. The first one, the historical
method, is to select an HTTP backend. The upgrade happens when the backend is
set. Thus, for in-place upgrades, only the backend configuration is considered
in the HTTP data processing. For destructive upgrades, the applicative stream
is destroyed, thus its processing is stopped. With this method, possibilities
to choose a backend with an HTTP/2 connection are really limited, as mentioned
above, and a bit useless because the stream is destroyed. The second method is
to upgrade during the tcp-request content rules evaluation, thanks to the
"switch-mode http" action. In this case, the upgrade is performed in the
frontend context and it is possible to define HTTP directives in this
frontend. For in-place upgrades, it offers all the power of the HTTP analysis
as soon as possible. It is not that far from an HTTP frontend. For destructive
upgrades, it does not change anything except it is useless to choose a backend
on limited information. It is of course the recommended method. Thus, testing
the request protocol from the tcp-request content rules to perform an HTTP
upgrade is enough. All the remaining HTTP manipulation may be moved to the
frontend http-request ruleset. But keep in mind that tcp-request content rules
remains evaluated on each streams, that can't be changed.
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 -
clitcpka-cnt X X X -
clitcpka-idle X X X -
clitcpka-intvl X 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
errorfiles 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-after-response - X X X
http-check comment X - X X
http-check connect X - X X
http-check disable-on-404 X - X X
http-check expect X - X X
http-check send X - X X
http-check send-state X - X X
http-check set-var X - X X
http-check unset-var X - X X
http-error X 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-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 disable-h2-upgrade (*) 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
option idle-close-on-response (*) 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
srvtcpka-cnt X - X X
srvtcpka-idle X - X X
srvtcpka-intvl 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 comment X - X X
tcp-check connect X - X X
tcp-check expect X - X X
tcp-check send X - X X
tcp-check send-lf X - X X
tcp-check send-binary X - X X
tcp-check send-binary-lf X - X X
tcp-check set-var X - X X
tcp-check unset-var X - 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. It will
also consider the number of queued connections in addition to
the established ones in order to minimize queuing.
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.
A "path-only" parameter indicates that the hashing key starts
at the first '/' of the path. This can be used to ignore the
authority part of absolute URIs, and to make sure that HTTP/1
and HTTP/2 URIs will provide the same hash.
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".
<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)