Network http pipelining


Network HTTP pipelining

http pipelining — технология, позволяющая удерживать TCP соединение и совершать повторную отправку данных не устанавливая его заново.

Чтобы использовать http pipelining поддержка должна быть на уровне пользовательского браузера и на уровне веб-сервера. На уровне браузера она практически всегда есть для мобильный устройств. Для Desktop она включена в Opera, для остальных браузеров нужно проверять и включать дополнительно.

Технология является частью протокола HTTP/1.1 и используется для создания сессии, позволяющей пересылать пакеты по сети между клиентом и сервером. Относясь к сетевому стэку технология используется по умолчанию в веб-серверах таких как Nginx.

Другая отличительная черта — возможность отправки следующего пакета информации не дожидаясь ответа, все это дает возможность более эффективно использовать сеть сокращая затрачиваемое количество ресурсов и увеличивая скорость.

В современных условиях необходимость в pipeliningпрактически отпала, на смену HTTP1.1 пришел новый протокол HTTP/2. Он использует мультиплексирование, т.е. TCP пакеты не отправляются по сети по одному и передаются через устанавливаемое соединение уплотняя его автоматически.

Повторная установка соединения каждый раз более не требуется, потому потерь времени нет и данные передаются максимально эффективно.

HTTP/2 активно внедряется и используется многими веб-серверами (основным требованием для протокола является безопасное соединение HTTPS).

Читайте подробнее про HTTP/2 и активацию протокола для Nginx

server-gu.ru

Connection management in HTTP/1.x

Connection management is a key topic in HTTP: opening and maintaining connections largely impacts the performance of Web sites and Web applications. In HTTP/1.x, there are several models: short-lived connections, persistent connections, and HTTP pipelining.

HTTP mostly relies on TCP for its transport protocol, providing a connection between the client and the server. In its infancy, HTTP used a single model to handle such connections. These connections were short-lived: a new one created each time a request needed sending, and closed once the answer had been received.

This simple model held an innate limitation on performance: opening each TCP connection is a resource-consuming operation. Several messages must be exchanged between the client and the server. Network latency and bandwidth affect performance when a request needs sending. Modern Web pages require many requests (a dozen or more) to serve the amount of information needed, proving this earlier model inefficient.

Two newer models were created in HTTP/1.1. The persistent-connection model keeps connections opened between successive requests, reducing the time needed to open new connections. The HTTP pipelining model goes one step further, by sending several successive requests without even waiting for an answer, reducing much of the latency in the network.

HTTP/2 adds additional models for connection management.

It's important point to note that connection management in HTTP applies to the connection between two consecutive nodes, which is hop-by-hop and not end-to-end. The model used in connections between a client and its first proxy may differ from the model between a proxy and the destination server (or any intermediate proxies). The HTTP headers involved in defining the connection model, like Connection and Keep-Alive, are hop-by-hop headers with their values able to be changed by intermediary nodes.

A related topic is the concept of HTTP connection upgrades, wherein an HTTP/1.1 connection is upgraded to a different protocol, such as TLS/1.0, WebSocket, or even HTTP/2 in cleartext. This protocol upgrade mechanism is documented in more detail elsewhere.

Short-lived connections

The original model of HTTP, and the default one in HTTP/1.0, is short-lived connections. Each HTTP request is completed on its own connection; this means a TCP handshake happens before each HTTP request, and these are serialized.

The TCP handshake itself is time-consuming, but a TCP connection adapts to its load, becoming more efficient with more sustained (or warm) connections. Short-lived connections do not make use of this efficiency feature of TCP, and performance degrades from optimum by persisting to transmit over a new, cold connection.

This model is the default model used in HTTP/1.0 (if there is no Connection header, or if its value is set to close). In HTTP/1.1, this model is only used when the Connection header is sent with a value of close.

Unless dealing with a very old system, which doesn't support a persistent connection, there is no compelling reason to use this model.

Persistent connections

Short-lived connections have two major hitches: the time taken to establish a new connection is significant, and performance of the underlying TCP connection gets better only when this connection has been in use for some time (warm connection). To ease these problems, the concept of a persistent connection has been designed, even prior to HTTP/1.1. Alternatively this may be called a keep-alive connection.

A persistent connection is one which remains open for a period of time, and can be reused for several requests, saving the need for a new TCP handshake, and utilizing TCP's performance enhancing capabilities. This connection will not stay open forever: idle connections are closed after some time (a server may use the Keep-Alive header to specify a minimum time the connection should be kept open).

Persistent connections also have drawbacks; even when idling they consume server resources, and under heavy load, DoS attacks can be conducted. In such cases, using non-persistent connections, which are closed as soon as they are idle, can provide better performance.

HTTP/1.0 connections are not persistent by default. Setting Connection to anything other than close, usually retry-after, will make them persistent.

In HTTP/1.1, persistence is the default, and the header is no longer needed (but it is often added as a defensive measure against cases requiring a fallback to HTTP/1.0).

HTTP pipelining

HTTP pipelining is not activated by default in modern browsers:

  • Buggy proxies are still common and these lead to strange and erratic behaviors that Web developers cannot foresee and diagnose easily.
  • Pipelining is complex to implement correctly: the size of the resource being transferred, the effective RTT that will be used, as well as the effective bandwidth, have a direct incidence on the improvement provided by the pipeline. Without knowing these, important messages may be delayed behind unimportant ones. The notion of important even evolves during page layout! HTTP pipelining therefore brings a marginal improvement in most cases only.
  • Pipelining is subject to the HOL problem.

For these reasons, pipelining has been superseded by a better algorithm, multiplexing, that is used by HTTP/2.

By default, HTTP requests are issued sequentially. The next request is only issued once the response to the current request has been received. As they are affected by network latencies and bandwidth limitations, this can result in significant delay before the next request is seen by the server.

Pipelining is the process to send successive requests, over the same persistent connection, without waiting for the answer. This avoids latency of the connection. Theoretically, performance could also be improved if two HTTP requests were to be packed into the same TCP message. The typical MSS (Maximum Segment Size), is big enough to contain several simple requests, although the demand in size of HTTP requests continues to grow.

Not all types of HTTP requests can be pipelined: only idempotent methods, that is GET, HEAD, PUT and DELETE, can be replayed safely: should a failure happen, the pipeline content can simply be repeated.

Today, every HTTP/1.1-compliant proxy and server should support pipelining, though many have limitations in practice: a significant reason no modern browser activates this feature by default.

Domain sharding

Unless you have a very specific immediate need, don't use this deprecated technique; switch to HTTP/2 instead. In HTTP/2, domain sharding is no longer useful: the HTTP/2 connection is able to handle parallel unprioritized requests very well. Domain sharding is even detrimental to performance. Most HTTP/2 implementations use a technique called connection coalescing to revert eventual domain sharding.

As an HTTP/1.x connection is serializing requests, even without any ordering, it can't be optimal without large enough available bandwidth. As a solution, browsers open several connections to each domain, sending parallel requests. Default was once 2 to 3 connections, but this has now increased to a more common use of 6 parallel connections. There is a risk of triggering DoS protection on the server side if attempting more than this number.

If the server wishes a faster Web site or application response, it is possible for the server to force the opening of more connections. For example, Instead of having all resources on the same domain, say www.example.com, it could split over several domains, www1.example.com, www2.example.com, www3.example.com. Each of these domains resolve to the same server, and the Web browser will open 6 connections to each (in our example, boosting the connections to 18). This technique is called domain sharding.

Conclusion

Improved connection management allows considerable boosting of performance in HTTP. With HTTP/1.1 or HTTP/1.0, using a persistent connection – at least until it becomes idle – leads to the best performance. However, the failure of pipelining has lead to designing superior connection management models, which have been incorporated into HTTP/2.

developer.mozilla.org

Speed Up Firefox By Enabling HTTP Pipelining

Mozilla Firefox is an impressive and speedy browser most of the time. However, there are times when its users are not happy with the rate in which it loads webpages. Not to worry! Here is a tweak that you can use to improve the speed of the browser.

It’s a simple tweak known simply as HTTP pipelining. What does it do? By default Firefox sends only one HTTP request per HTTP connection it makes. When you enable this hidden feature, you’ll be telling Firefox that it can send multiple requests at a time. Doing this will improve the speed in which your browser loads pages.

Enable HTTP pipelining

Turning on HTTP pipelining is a fairly simple process. Just open a new tab in Firefox, put about:config into the address bar and press the Enter key on your keyboard.

One you’ve made it to about:config, you’ll see a warning. Accept it to be brought to the Firefox browser configuration area.

Inside this configuration area, click on the search box and enter network.http.pipelining. Once it’s entered, you should see it pop up.

When you see what you’ve searched for, you’ll notice that it’s set to false. Double click on it and you’ll be able to set “network.http.pipelining” to “true,” thus enabling HTTP pipelining.

Enable HTTP pipelining behind a proxy

If the network you are connected to is located behind a proxy of some sort, you’ll need to do an additional step for this to work. Inside the about:config window, search for network.http.proxy.pipelining.

Just like before, you’ll need to double-click on what you’ve searched for inside about:config to enable it. After that, HTTP pipelining should be enabled on proxies!

Other ways to speed up Firefox

Besides just enabling HTTP pipelining to reduce the latency between loading web pages, there are other ways that you can quickly make your Firefox installation a little bit faster.

One thing you can do is force your browser to use Mozilla’s new HTTP cache system. It’s not enabled by default but by opening up a browser tab and heading over to about:config.

Once you’re there, enter browser.cache.use_new_backend into the search box. It should pop up fairly quickly.

Move your mouse over to the “0” and right click on it. A context menu should pop up. Inside this context menu, just click the modify option.

Doing this will bring up a text box with “0” already inside it. Change the “0” to a “1” and press the OK button. After this is done, Firefox should be using the new caching system.

Conclusion

Personally, I love Firefox and its speed, but for those who are obsessed with making web pages load even quicker than the defaults, tweaking Firefox in this way is totally warranted.

I hope that by following these few tricks you’ll be able to make Firefox just a little bit faster.

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Additional System Details

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

  • Do NOT click the Reset button on the Safe Mode start window.

Your System Details List shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts.

The user.js file is only present if you or other software has created this file and normally it wouldn't be there. You can check its content with a plain text editor (right-click: Open with) if you didn't create this file yourself.

The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

If you do not keep changes after a restart or otherwise have problems with preferences, see:

  • http://kb.mozillazine.org/Preferences_not_saved

Start Firefox in [[Safe Mode|Safe Mode]] to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance). *Do NOT click the Reset button on the Safe Mode start window. *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes ---- Your System Details List shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts. The user.js file is only present if you or other software has created this file and normally it wouldn't be there. You can check its content with a plain text editor (right-click: Open with) if you didn't create this file yourself. The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session. If you do not keep changes after a restart or otherwise have problems with preferences, see: *http://kb.mozillazine.org/Preferences_not_saved

support.mozilla.org

Database Users

Can anyone give some advices or something in order to try to implement in Java HTTP pipelining. How can I do this and what are the main tasks that I have to complete in order to have a client and a server communicating and sending data with HTTP pipelining. Please I really need to learn this is very important if someone can help. Regards This article: http://en.wikipedia.org/wiki/HTTP_pipelining appears to cover the basics of the topic. Have you read it? From your post it isn't clear whether you know anything about the topic or not. sorry i wasn't accurate enough. I know the general algorithm of http pipelining i was just looking a pseudo code in java in order to implemented or somethinh to help me think how can i implemented it. Ah so you want teh codes™. If you understand it as you say you do then you have no need for them. Just do it. It's not exactly rocket science. If you have a SPECIFIC question about some part you don't understand then you should ask a specific question. Ok specific question. The implementation should take place using threads or not. For example i have the HTTP pipe open ok the streaming of the messages should just be by calling the sendmessage() class that i have used for instance or should i invoke a new thread for each pipelined message that i send? And if is with threads will I use the PipedOutWriter and Reader or the usual ones? I am not trying to take any codes or smth its just is my first program that i am trying to write in java... i used to program in C so its totally different and that is why i asked for a pseudo code or smth to just get me into the spirit of how to think to solve this. I know its not a rocket scince problem to u but to me its pretty difficult.:( sorry to dissapoint you. Previous Page | Networking | HOME

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