HTTP pipelining: Difference between revisions

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Revision as of 17:42, 9 September 2021 editDanCherek (talk \| contribs)Autopatrolled, Administrators74,546 editsm Disambiguating links to Lag (link changed to Latency (engineering)) using DisamAssist.← Previous edit		Revision as of 17:17, 19 September 2021 edit undoKaltenmeyer (talk \| contribs)Extended confirmed users118,181 editsm →Other implementations: typoTag: AWB Next edit →
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	*IceBreak application server since BUILD389		*IceBreak application server since BUILD389
	*phttpget from ] (a minimalist pipelined HTTP client)<ref></ref>		*phttpget from ] (a minimalist pipelined HTTP client)<ref></ref>
	*] previously had limited support for pipelining using the CURLMOPT_PIPELINING option,<ref> {{webarchive\|url=https://web.archive.org/web/20120627181619/http://curl.haxx.se/dev/readme-pipelining.html\|date=2012-06-27}}, Curl developer documentation</ref> but this support was removed in ~~vesion~~ 7.65.0<ref>{{webarchive\|url=https://web.archive.org/web/20210205184800/https://daniel.haxx.se/blog/2019/04/06/curl-says-bye-bye-to-pipelining/\|date=2021-02-05}}</ref>		*] previously had limited support for pipelining using the CURLMOPT_PIPELINING option,<ref> {{webarchive\|url=https://web.archive.org/web/20120627181619/http://curl.haxx.se/dev/readme-pipelining.html\|date=2012-06-27}}, Curl developer documentation</ref> but this support was removed in version 7.65.0<ref>{{webarchive\|url=https://web.archive.org/web/20210205184800/https://daniel.haxx.se/blog/2019/04/06/curl-says-bye-bye-to-pipelining/\|date=2021-02-05}}</ref>
	*] (a ] ] distribution system)		*] (a ] ] distribution system)
	*] (APT) supports pipelining.{{Citation needed\|date=August 2010}}		*] (APT) supports pipelining.{{Citation needed\|date=August 2010}}

Revision as of 17:17, 19 September 2021

HTTP

Persistence Compression HTTPS QUIC
Request methods
OPTIONS GET HEAD POST PUT DELETE TRACE CONNECT PATCH
Header fields
Cookie ETag Location HTTP referer DNT X-Forwarded-For
Response status codes
301 Moved Permanently 302 Found 303 See Other 403 Forbidden 404 Not Found 451 Unavailable for Legal Reasons
Security access control methods
Basic access authentication Digest access authentication
Security vulnerabilities
HTTP header injection HTTP request smuggling HTTP response splitting HTTP parameter pollution
v t e

HTTP pipelining is a feature of HTTP/1.1 which allows multiple HTTP requests to be sent over a single TCP (transmission control protocol) connection without waiting for the corresponding responses. HTTP/1.1 specification requires servers to respond to pipelined requests correctly, sending back non-pipelined but valid responses even if server does not support HTTP pipelining. Despite this requirement, many legacy HTTP/1.1 servers do not support pipelining correctly, forcing most HTTP clients to not use HTTP pipelining in practice.

The technique was superseded by multiplexing via HTTP/2, which is supported by most modern browsers.

In HTTP/3, the multiplexing is accomplished through the new underlying QUIC transport protocol, which replaces TCP. This further reduces loading time, as there is no head-of-line blocking anymore.

Motivation and limitations

The pipelining of requests results in a dramatic improvement in the loading times of HTML pages, especially over high latency connections such as satellite Internet connections. The speedup is less apparent on broadband connections, as the limitation of HTTP 1.1 still applies: the server must send its responses in the same order that the requests were received—so the entire connection remains first-in-first-out and HOL blocking can occur. The asynchronous operation of HTTP/2 and SPDY are solutions for this. Browsers ultimately did not enable pipelining by default, and by 2017 most browsers supported HTTP/2 by default which used multiplexing instead.

Non-idempotent requests, like those using POST, should not be pipelined. Sequences of GET and HEAD requests can always be pipelined. A sequence of other idempotent requests like PUT and DELETE can be pipelined or not depending on whether requests in the sequence depend on the effect of others.

HTTP pipelining requires both the client and the server to support it. HTTP/1.1 conforming servers are required to support pipelining. This does not mean that servers are required to pipeline responses, but that they are required not to fail if a client chooses to pipeline requests.

Implementation status

Pipelining was introduced in HTTP/1.1 and was not present in HTTP/1.0.

Implementation in web servers

Implementing pipelining in web servers is a relatively simple matter of making sure that network buffers are not discarded between requests. For that reason, most modern web servers handle pipelining without any problem.

Implementation in web browsers

Of all the major browsers, only Opera based on Presto layout engine had a fully working implementation that was enabled by default. In all other browsers HTTP pipelining is disabled or not implemented.

Internet Explorer 8 does not pipeline requests, due to concerns regarding buggy proxies and head-of-line blocking.
Internet Explorer 11 does not support pipelining.
Mozilla browsers (such as Mozilla Firefox, SeaMonkey and Camino) support pipelining; however, it is disabled by default. Pipelining is disabled by default to avoid issues with misbehaving servers. When pipelining is enabled, Mozilla browsers use some heuristics, especially to turn pipelining off for older IIS servers. Support for H1 Pipeline was removed from Mozilla Firefox in Version 54.
Konqueror 2.0 supports pipelining, but disabled by default.
Google Chrome previously supported pipelining, but it has been disabled due to bugs and problems with poorly behaving servers.
Pale Moon (web browser) supports pipelining, and is enabled by default.

Implementation in web proxies

Most HTTP proxies do not pipeline outgoing requests.

Some versions of the Squid web proxy will pipeline up to two outgoing requests. This functionality has been disabled by default and needs to be manually enabled for "bandwidth management and access logging reasons". Squid supports multiple requests from clients.

The Polipo proxy pipelines outgoing requests.

Tempesta FW, an open source application delivery controller, also pipelines requests to backend servers.

Other implementations

The libwww library made by the World Wide Web Consortium (W3C), supports pipelining since version 5.1 released at 18 February 1997.

Other application development libraries that support HTTP pipelining include:

Perl modules providing client support for HTTP pipelining are HTTP::Async and the LWPng (libwww-perl New Generation) library.
The Microsoft .NET Framework 3.5 supports HTTP pipelining in the module System.Net.HttpWebRequest.
Qt class QNetworkRequest, introduced in 4.4.

Some other applications currently exploiting pipelining are:

IceBreak application server since BUILD389
phttpget from FreeBSD (a minimalist pipelined HTTP client)
libcurl previously had limited support for pipelining using the CURLMOPT_PIPELINING option, but this support was removed in version 7.65.0
portsnap (a FreeBSD ports tree distribution system)
Advanced Packaging Tool (APT) supports pipelining.
Subversion (SVN) has optional support for HTTP pipelining with the serf WebDAV access module (the default module, neon, does not have pipelining support).
Microsoft Message Queuing on Windows Server 2003 utilises pipelining on HTTP by default, and can be configured to use it on HTTPS.
IBM CICS 3.1 supports HTTP pipelining within its client.