HTTP pipelining: Difference between revisions

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imported>Steel1943
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imported>Unixxx
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[[File:HTTP pipelining2.svg|thumb|right|300px|Time diagram of non-pipelined vs. pipelined connection]]
[[File:HTTP pipelining2.svg|thumb|right|300px|Time diagram of non-pipelined vs. pipelined connection]]
{{HTTP}}
{{HTTP}}
'''HTTP pipelining''' is a feature of '''HTTP/1.1''', which allows multiple [[HTTP]] requests to be sent over a single [[Transmission Control Protocol|TCP]] connection without waiting for the corresponding responses.<ref name="HTTP/1.1-pipelining">{{cite journal|url=http://tools.ietf.org/html/rfc7230#section-6.3.2|title=Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing: Pipelining|year=2014 |publisher=ietf.org|doi=10.17487/RFC7230 |accessdate=2014-07-24|editor-last1=Fielding |editor-last2=Reschke |editor-first1=R. |editor-first2=J. |last1=Fielding |first1=R. |last2=Reschke |first2=J. |doi-access=free |url-access=subscription }}</ref> HTTP/1.1 requires servers to respond to pipelined requests correctly, with 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.
'''HTTP pipelining''' is a feature of '''HTTP/1.1''' that allows multiple [[HTTP]] requests to be sent over a single [[Transmission Control Protocol|TCP]] connection without waiting for the corresponding responses.<ref name="HTTP/1.1-pipelining">{{cite journal|url=http://tools.ietf.org/html/rfc7230#section-6.3.2|title=Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing: Pipelining|year=2014 |publisher=ietf.org|doi=10.17487/RFC7230 |accessdate=2014-07-24|editor-last1=Fielding |editor-last2=Reschke |editor-first1=R. |editor-first2=J. |last1=Fielding |first1=R. |last2=Reschke |first2=J. |doi-access=free |url-access=subscription }}</ref> HTTP/1.1 requires servers to respond to pipelined requests correctly, with non-pipelined but valid responses even if the server does not support HTTP pipelining. Despite this requirement, many legacy HTTP/1.1 servers do not support pipelining correctly, forcing most HTTP clients not to use HTTP pipelining.


The technique was superseded by '''[[multiplexing]]''' via [[HTTP/2]],<ref name=":0">{{Cite web|url=https://developer.mozilla.org/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x$revision/1330814|title=Revision 1330814 {{!}} Connection management in HTTP/1.x {{!}} MDN|website=MDN Web Docs|language=en-US|access-date=2018-03-19|archive-date=2018-03-19|archive-url=https://web.archive.org/web/20180319213834/https://developer.mozilla.org/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x$revision/1330814|url-status=dead}}</ref> which is supported by most modern [[Web browser|browsers]].<ref name="browser_support">{{cite web|url=http://caniuse.com/#search=http2|title=HTTP2 browser support|accessdate=March 9, 2017}}</ref>
The technique was superseded by '''[[multiplexing]]''' via [[HTTP/2]],<ref name=":0">{{Cite web|url=https://developer.mozilla.org/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x$revision/1330814|title=Revision 1330814 {{!}} Connection management in HTTP/1.x {{!}} MDN|website=MDN Web Docs|language=en-US|access-date=2018-03-19|archive-date=2018-03-19|archive-url=https://web.archive.org/web/20180319213834/https://developer.mozilla.org/en-US/docs/Web/HTTP/Connection_management_in_HTTP_1.x$revision/1330814|url-status=dead}}</ref> which is supported by most modern [[Web browser|browsers]].<ref name="browser_support">{{cite web|url=http://caniuse.com/#search=http2|title=HTTP2 browser support|accessdate=March 9, 2017}}</ref>
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Pipelining was introduced in HTTP/1.1 and was not present in HTTP/1.0.<ref>{{Cite web |url=http://www8.org/w8-papers/5c-protocols/key/key.html |title=Key Differences between HTTP/1.0 and HTTP/1.1 |access-date=2016-04-16 |archive-url=https://web.archive.org/web/20160424204340/http://www8.org/w8-papers/5c-protocols/key/key.html |archive-date=2016-04-24 |url-status=dead }}</ref>
Pipelining was introduced in HTTP/1.1 and was not present in HTTP/1.0.<ref>{{Cite web |url=http://www8.org/w8-papers/5c-protocols/key/key.html |title=Key Differences between HTTP/1.0 and HTTP/1.1 |access-date=2016-04-16 |archive-url=https://web.archive.org/web/20160424204340/http://www8.org/w8-papers/5c-protocols/key/key.html |archive-date=2016-04-24 |url-status=dead }}</ref>


There have always been complaints about browsers, proxy servers, etc. not working well when using pipelined requests / responses, up to the point that for many years (at least till 2011) software developers, engineers, web experts, etc. tried to summarize the various kind of problems they noted, to fix things and to give advices about how to deal with pipelining on the Open Web.<ref name="make-pipelining-usable">{{Cite web|url= https://www.ietf.org/archive/id/draft-nottingham-http-pipeline-01.html|title=Making HTTP Pipelining Usable on the Open Web|date=March 14, 2011|author=Mark Nottingham|accessdate= October 16, 2021}}</ref>
There have always been complaints about browsers, proxy servers, etc. not working well when using pipelined requests / responses, up to the point that for many years (at least until 2011) software developers, engineers, web experts, etc. tried to summarize the various kind of problems they noted, to fix things and to give advices about how to deal with pipelining on the Open Web.<ref name="make-pipelining-usable">{{Cite web|url= https://www.ietf.org/archive/id/draft-nottingham-http-pipeline-01.html|title=Making HTTP Pipelining Usable on the Open Web|date=March 14, 2011|author=Mark Nottingham|accessdate= October 16, 2021}}</ref>


===Implementation in web browsers===
===Implementation in web browsers===
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Most HTTP proxies do not pipeline outgoing requests.<ref>{{cite web|url= https://www.mnot.net/blog/2007/06/20/proxy_caching|title=The State of Proxy Caching|date=June 20, 2007|author=Mark Nottingham|accessdate= May 16, 2009}}</ref>
Most HTTP proxies do not pipeline outgoing requests.<ref>{{cite web|url= https://www.mnot.net/blog/2007/06/20/proxy_caching|title=The State of Proxy Caching|date=June 20, 2007|author=Mark Nottingham|accessdate= May 16, 2009}}</ref>


Some HTTP proxies, including transparent HTTP proxies, may manage pipelined requests very badly (e.g. by mixing up the order of pipelined responses).<ref>{{cite web|url= https://www.mnot.net/blog/2011/07/11/what_proxies_must_do|title=What proxies must do|date=July 11, 2011|author=Mark Nottingham|accessdate= October 16, 2021}}</ref>
Some HTTP proxies, including transparent HTTP proxies, may manage pipelined requests very badly (e.g. by mixing up the order of pipelined responses).<ref>{{cite web|url= https://www.mnot.net/blog/2011/07/11/what_proxies_must_do|title=What proxies must do|date=July 11, 2011|author=Mark Nottingham|work=Mark Nottingham |accessdate= October 16, 2021}}</ref>


Some versions of the [[Squid (software)|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".<ref>{{cite web|url=http://www.squid-cache.org/Doc/config/pipeline_prefetch/|title=squid : pipeline_prefetch configuration directive|date=November 9, 2009|publisher=[[Squid (software)|Squid]]|accessdate=December 1, 2009}}</ref> Squid supports multiple requests from clients.
Some versions of the [[Squid (software)|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".<ref>{{cite web|url=http://www.squid-cache.org/Doc/config/pipeline_prefetch/|title=squid : pipeline_prefetch configuration directive|date=November 9, 2009|publisher=[[Squid (software)|Squid]]|accessdate=December 1, 2009}}</ref> Squid supports multiple requests from clients.

Latest revision as of 03:17, 30 November 2025

Template:Short description

File:HTTP pipelining2.svg
Time diagram of non-pipelined vs. pipelined connection

Script error: No such module "Sidebar". HTTP pipelining is a feature of HTTP/1.1 that allows multiple HTTP requests to be sent over a single TCP connection without waiting for the corresponding responses.[1] HTTP/1.1 requires servers to respond to pipelined requests correctly, with non-pipelined but valid responses even if the server does not support HTTP pipelining. Despite this requirement, many legacy HTTP/1.1 servers do not support pipelining correctly, forcing most HTTP clients not to use HTTP pipelining.

The technique was superseded by multiplexing via HTTP/2,[2] which is supported by most modern browsers.[3]

In HTTP/3, multiplexing is accomplished via QUIC which replaces TCP. This further reduces loading time, as there is no head-of-line blocking even if some packets are lost.

Motivation and limitations

The pipelining of requests results in a dramatic improvement[4] 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[1] and HOL blocking can occur.

The asynchronous operations of HTTP/2 and SPDY are solution for this.[5] By 2017 most browsers supported HTTP/2 by default which uses multiplexing instead.[2]

Non-idempotent requests such as POST should not be pipelined.[6] Read requests like GET and HEAD 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.[1]

HTTP pipelining requires both the client and the server to support it. HTTP/1.1 conforming servers are required to produce valid responses to pipelined requests, but may not actually process requests concurrently.[7]

Most pipelining problems happen in HTTP intermediate nodes (hop-by-hop), i.e. in proxy servers, especially in transparent proxy servers (if one of them along the HTTP chain does not handle pipelined requests properly then nothing works as it should).[8]

Using pipelining with HTTP proxy servers is usually not recommended also because the HOL blocking problem may really slow down proxy server responses (as the server responses must be in the same order of the received requests).[1][9]

Example: if a client sends 4 pipelined GET requests to a proxy through a single connection and the first one is not in its cache then the proxy has to forward that request to the destination web server; if the following three requests are instead found in its cache, the proxy has to wait for the web server response, then it has to send it to the client and only then it can send the three cached responses too.

If instead a client opens 4 connections to a proxy and sends 1 GET request per connection (without using pipelining) the proxy can send the three cached responses to client in parallel before the response from server is received, decreasing the overall completion time (because requests are served in parallel with no head-of-line blocking problem).[10] The same advantage exists in HTTP/2 multiplexed streams.

Implementation status

Pipelining was introduced in HTTP/1.1 and was not present in HTTP/1.0.[11]

There have always been complaints about browsers, proxy servers, etc. not working well when using pipelined requests / responses, up to the point that for many years (at least until 2011) software developers, engineers, web experts, etc. tried to summarize the various kind of problems they noted, to fix things and to give advices about how to deal with pipelining on the Open Web.[8]

Implementation in web browsers

Of all the major browsers, only Opera had a fully working implementation that was enabled by default. In other browsers HTTP pipelining was disabled or not implemented.[5]

Implementation in web proxy servers

Most HTTP proxies do not pipeline outgoing requests.[19]

Some HTTP proxies, including transparent HTTP proxies, may manage pipelined requests very badly (e.g. by mixing up the order of pipelined responses).[20]

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".[21] Squid supports multiple requests from clients.

The Polipo proxy pipelines outgoing requests.[22]

Tempesta FW, an open source application delivery controller,[23] also pipelines requests to backend servers.[24]

Other implementations

The libwww library made by the World Wide Web Consortium (W3C), supports pipelining since version 5.1 released at 18 February 1997.[25]

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.[26]
  • The Microsoft .NET Framework 3.5 supports HTTP pipelining in the module System.Net.HttpWebRequest.[27]
  • Qt class QNetworkRequest, introduced in 4.4.[28]

Some other applications currently exploiting pipelining are:

  • IceBreak application server since BUILD389
  • phttpget from FreeBSD (a minimalist pipelined HTTP client)[29]
  • libcurl previously had limited support for pipelining using the CURLMOPT_PIPELINING option,[30] but this support was removed in version 7.65.0[31]
  • portsnap (a FreeBSD ports tree distribution system)
  • Advanced Packaging Tool (APT) supports pipelining.Script error: No such module "Unsubst".
  • Subversion (SVN) has optional support for HTTP pipelining with the serf WebDAV access module (the default module, neon, does not have pipelining support).[32][33]
  • Microsoft Message Queuing on Windows Server 2003 utilises pipelining on HTTP by default, and can be configured to use it on HTTPS.[34]
  • IBM CICS 3.1 supports HTTP pipelining within its client.[35]

Testing tools which support HTTP pipelining include:

See also

References

<templatestyles src="Reflist/styles.css" />

  1. ↑ a b c d Script error: No such module "Citation/CS1".
  2. ↑ a b Script error: No such module "citation/CS1".
  3. ↑ Script error: No such module "citation/CS1".
  4. ↑ Script error: No such module "citation/CS1".
  5. ↑ a b Script error: No such module "citation/CS1".
  6. ↑ Script error: No such module "citation/CS1".
  7. ↑ Script error: No such module "citation/CS1".
  8. ↑ a b Script error: No such module "citation/CS1".
  9. ↑ a b Script error: No such module "citation/CS1".
  10. ↑ Script error: No such module "Citation/CS1".
  11. ↑ Script error: No such module "citation/CS1".
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ Firefox 54 Release Notes
  14. ↑ Script error: No such module "citation/CS1".
  15. ↑ Script error: No such module "citation/CS1".
  16. ↑ Script error: No such module "citation/CS1".
  17. ↑ HTTP Pipelining - The Chromium Projects
  18. ↑ Script error: No such module "citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".
  20. ↑ Script error: No such module "citation/CS1".
  21. ↑ Script error: No such module "citation/CS1".
  22. ↑ Script error: No such module "citation/CS1".
  23. ↑ Script error: No such module "citation/CS1".
  24. ↑ Script error: No such module "citation/CS1".
  25. ↑ Script error: No such module "citation/CS1".
  26. ↑ Script error: No such module "citation/CS1".
  27. ↑ System.Net.HttpWebRequest & pipelining
  28. ↑ QNetworkRequest Class Reference Template:Webarchive, Nokia QT documentation
  29. ↑ Pipelined HTTP GET utility
  30. ↑ Curl pipelining explanation Template:Webarchive, Curl developer documentation
  31. ↑ Curl pipelining removal announcementTemplate:Webarchive
  32. ↑ Script error: No such module "citation/CS1".
  33. ↑ Script error: No such module "citation/CS1".
  34. ↑ Script error: No such module "citation/CS1".
  35. ↑ How CICS Web support handles pipelining
  36. ↑ Script error: No such module "citation/CS1".
  37. ↑ Script error: No such module "citation/CS1".

Script error: No such module "Check for unknown parameters".

External links

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