haproxy-1.4.24

---------------------- HAProxy Configuration Manual ---------------------- version 1.4.24 willy tarreau 2013/06/17 This document covers the configuration language as implemented in the version specified above. It does not provide any hint, example or advice. For such documentation, please refer to the Reference Manual or the Architecture Manual. The summary below is meant to help you search sections by name and navigate through the document. Note to documentation contributors : This document is formated with 80 columns per line, with even number of spaces for indentation and without tabs. Please follow these rules strictly so that it remains easily printable everywhere. If a line needs to be printed verbatim and does not fit, please end each line with a backslash ('\') and continue on next line. If you add sections, please update the summary below for easier searching. Summary ------- 1. Quick reminder about HTTP 1.1. The HTTP transaction model 1.2. HTTP request 1.2.1. The Request line 1.2.2. The request headers 1.3. HTTP response 1.3.1. The Response line 1.3.2. The response headers 2. Configuring HAProxy 2.1. Configuration file format 2.2. Time format 2.3. Examples 3. Global parameters 3.1. Process management and security 3.2. Performance tuning 3.3. Debugging 3.4. Userlists 4. Proxies 4.1. Proxy keywords matrix 4.2. Alphabetically sorted keywords reference 5. Server and default-server options 6. HTTP header manipulation 7. Using ACLs and pattern extraction 7.1. Matching integers 7.2. Matching strings 7.3. Matching regular expressions (regexes) 7.4. Matching IPv4 addresses 7.5. Available matching criteria 7.5.1. Matching at Layer 4 and below 7.5.2. Matching contents at Layer 4 7.5.3. Matching at Layer 7 7.6. Pre-defined ACLs 7.7. Using ACLs to form conditions 7.8. Pattern extraction 8. Logging 8.1. Log levels 8.2. Log formats 8.2.1. Default log format 8.2.2. TCP log format 8.2.3. HTTP log format 8.3. Advanced logging options 8.3.1. Disabling logging of external tests 8.3.2. Logging before waiting for the session to terminate 8.3.3. Raising log level upon errors 8.3.4. Disabling logging of successful connections 8.4. Timing events 8.5. Session state at disconnection 8.6. Non-printable characters 8.7. Capturing HTTP cookies 8.8. Capturing HTTP headers 8.9. Examples of logs 9. Statistics and monitoring 9.1. CSV format 9.2. Unix Socket commands 1. Quick reminder about HTTP ---------------------------- When haproxy is running in HTTP mode, both the request and the response are fully analyzed and indexed, thus it becomes possible to build matching criteria on almost anything found in the contents. However, it is important to understand how HTTP requests and responses are formed, and how HAProxy decomposes them. It will then become easier to write correct rules and to debug existing configurations. 1.1. The HTTP transaction model ------------------------------- The HTTP protocol is transaction-driven. This means that each request will lead to one and only one response. Traditionally, a TCP connection is established from the client to the server, a request is sent by the client on the connection, the server responds and the connection is closed. A new request will involve a new connection : [CON1] [REQ1] ... [RESP1] [CLO1] [CON2] [REQ2] ... [RESP2] [CLO2] ... In this mode, called the "HTTP close" mode, there are as many connection establishments as there are HTTP transactions. Since the connection is closed by the server after the response, the client does not need to know the content length. Due to the transactional nature of the protocol, it was possible to improve it to avoid closing a connection between two subsequent transactions. In this mode however, it is mandatory that the server indicates the content length for each response so that the client does not wait indefinitely. For this, a special header is used: "Content-length". This mode is called the "keep-alive" mode : [CON] [REQ1] ... [RESP1] [REQ2] ... [RESP2] [CLO] ... Its advantages are a reduced latency between transactions, and less processing power required on the server side. It is generally better than the close mode, but not always because the clients often limit their concurrent connections to a smaller value. A last improvement in the communications is the pipelining mode. It still uses keep-alive, but the client does not wait for the first response to send the second request. This is useful for fetching large number of images composing a page : [CON] [REQ1] [REQ2] ... [RESP1] [RESP2] [CLO] ... This can obviously have a tremendous benefit on performance because the network latency is eliminated between subsequent requests. Many HTTP agents do not correctly support pipelining since there is no way to associate a response with the corresponding request in HTTP. For this reason, it is mandatory for the server to reply in the exact same order as the requests were received. By default HAProxy operates in a tunnel-like mode with regards to persistent connections: for each connection it processes the first request and forwards everything else (including additional requests) to selected server. Once established, the connection is persisted both on the client and server sides. Use "option http-server-close" to preserve client persistent connections while handling every incoming request individually, dispatching them one after another to servers, in HTTP close mode. Use "option httpclose" to switch both sides to HTTP close mode. "option forceclose" and "option http-pretend-keepalive" help working around servers misbehaving in HTTP close mode. 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. -