diff options
| author | Loïc Hoguin <[email protected]> | 2016-03-28 15:36:42 +0200 |
|---|---|---|
| committer | Loïc Hoguin <[email protected]> | 2016-03-28 15:36:42 +0200 |
| commit | fe3492a98de29942477b061cd02c92246f4bf85a (patch) | |
| tree | 2255b796a657e6e4dfb72beec1141258d17f1220 /docs/en/cowboy/2.0/guide/overview | |
| download | ninenines.eu-fe3492a98de29942477b061cd02c92246f4bf85a.tar.gz ninenines.eu-fe3492a98de29942477b061cd02c92246f4bf85a.tar.bz2 ninenines.eu-fe3492a98de29942477b061cd02c92246f4bf85a.zip | |
Initial commit, new website system
Diffstat (limited to 'docs/en/cowboy/2.0/guide/overview')
| -rw-r--r-- | docs/en/cowboy/2.0/guide/overview/index.html | 285 |
1 files changed, 285 insertions, 0 deletions
diff --git a/docs/en/cowboy/2.0/guide/overview/index.html b/docs/en/cowboy/2.0/guide/overview/index.html new file mode 100644 index 00000000..70a191dd --- /dev/null +++ b/docs/en/cowboy/2.0/guide/overview/index.html @@ -0,0 +1,285 @@ +<!DOCTYPE html> +<html lang="en"> + +<head> + <meta charset="utf-8"> + <meta name="viewport" content="width=device-width, initial-scale=1.0"> + <meta name="description" content=""> + <meta name="author" content="Loïc Hoguin based on a design from (Soft10) Pol Cámara"> + + <meta name="generator" content="Hugo 0.15" /> + + <title>Nine Nines: Request overview</title> + + <link href='http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + + <link href="/css/bootstrap.min.css" rel="stylesheet"> + <link href="/css/99s.css" rel="stylesheet"> + + <link rel="shortcut icon" href="/img/ico/favicon.ico"> + <link rel="apple-touch-icon-precomposed" sizes="114x114" href="/img/ico/apple-touch-icon-114.png"> + <link rel="apple-touch-icon-precomposed" sizes="72x72" href="/img/ico/apple-touch-icon-72.png"> + <link rel="apple-touch-icon-precomposed" href="/img/ico/apple-touch-icon-57.png"> + + +</head> + + +<body class=""> + <header id="page-head"> + <div id="topbar" class="container"> + <div class="row"> + <div class="span2"> + <h1 id="logo"><a href="/" title="99s">99s</a></h1> + </div> + <div class="span10"> + + <div id="side-header"> + <nav> + <ul> + <li><a title="Hear my thoughts" href="/articles">Articles</a></li> + <li><a title="Watch my talks" href="/talks">Talks</a></li> + <li class="active"><a title="Read the docs" href="/docs">Documentation</a></li> + <li><a title="Request my services" href="/services">Consulting & Training</a></li> + </ul> + </nav> + <ul id="social"> + <li> + <a href="https://github.com/ninenines" title="Check my Github repositories"><img src="/img/ico_github.png" data-hover="/img/ico_github_alt.png" alt="Github"></a> + </li> + <li> + <a title="Keep in touch!" href="http://twitter.com/lhoguin"><img src="/img/ico_microblog.png" data-hover="/img/ico_microblog_alt.png"></a> + </li> + <li> + <a title="Contact me" href="mailto:[email protected]"><img src="/img/ico_mail.png" data-hover="/img/ico_mail_alt.png"></a> + </li> + </ul> + </div> + </div> + </div> + </div> + + +</header> + +<div id="contents" class="two_col"> +<div class="container"> +<div class="row"> +<div id="docs" class="span9 maincol"> + +<h1 class="lined-header"><span>Request overview</span></h1> + +<div class="paragraph"><p>This chapter explains the different steps a request
+goes through until a response is sent, along with
+details of the Cowboy implementation.</p></div>
+<div class="sect1">
+<h2 id="_request_response">Request/response</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>As you already know, HTTP clients connect to the server and
+send a request for a resource; the server then sends a
+response containing the resource if it could obtain it.</p></div>
+<div class="paragraph"><p>Before the server can send the resource, however, it
+needs to perform many different operations to read the
+request, find the resource, prepare the response being
+sent and often other related operations the user can
+add like writing logs.</p></div>
+<div class="paragraph"><p>Requests take the following route in Cowboy:</p></div>
+<div class="imageblock">
+<div class="content">
+<img src="../http_req_resp.png" alt="HTTP request/response flowchart" />
+</div>
+</div>
+<div class="paragraph"><p>This shows the default middlewares, but they may be
+configured differently in your setup. The dark green
+indicates the points where you can hook your own code,
+the light green is the Cowboy code that you can of
+course configure as needed.</p></div>
+<div class="paragraph"><p>The <code>acceptor</code> is the part of the server that accepts
+the connection and create an Erlang process to handle
+it. The <code>parser</code> then starts reading from the socket
+and handling requests as they come until the socket
+is closed.</p></div>
+<div class="paragraph"><p>A response may be sent at many different points in the
+life of the request. If Cowboy can’t parse the request,
+it gives up with an error response. If the router can’t
+find the resource, it sends a not found error. Your
+own code can of course send a response at any time.</p></div>
+<div class="paragraph"><p>When a response is sent, you can optionally modify it
+or act upon it by enabling the <code>onresponse</code> hook. By
+default the response is sent directly to the client.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_and_then">And then?</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Behavior depends on what protocol is in use.</p></div>
+<div class="paragraph"><p>HTTP/1.0 can only process one request per connection,
+so Cowboy will close the connection immediately after
+it sends the response.</p></div>
+<div class="paragraph"><p>HTTP/1.1 allows the client to request that the server
+keeps the connection alive. This mechanism is described
+in the next section.</p></div>
+<div class="paragraph"><p>HTTP/2 is designed to allow sending multiple requests
+asynchronously on the same connection. Details on what
+this means for your application is described in this
+chapter.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_keep_alive_http_1_1">Keep-alive (HTTP/1.1)</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>With HTTP/1.1, the connection may be left open for
+subsequent requests to come. This mechanism is called
+<code>keep-alive</code>.</p></div>
+<div class="paragraph"><p>When the client sends a request to the server, it includes
+a header indicating whether it would like to leave the
+socket open. The server may or may not accept, indicating
+its choice by sending the same header in the response.</p></div>
+<div class="paragraph"><p>Cowboy will include this header automatically in all
+responses to HTTP/1.1 requests. You can however force
+the closing of the socket if you want. When Cowboy sees
+you want to send a <code>connection: close</code> header, it will
+not override it and will close the connection as soon
+as the reply is sent.</p></div>
+<div class="paragraph"><p>This snippet will force Cowboy to close the connection.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">Req2</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_req:reply</span></span>(<span style="color: #993399">200</span>, [
+ {<span style="color: #990000"><<</span><span style="color: #FF0000">"connection"</span><span style="color: #990000">>></span>, <span style="color: #990000"><<</span><span style="color: #FF0000">"close"</span><span style="color: #990000">>></span>},
+], <span style="color: #990000"><<</span><span style="color: #FF0000">"Closing the socket in 3.. 2.. 1.."</span><span style="color: #990000">>></span>, <span style="color: #009900">Req</span>)<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Cowboy will only accept a certain number of new requests
+on the same connection. By default it will run up to 100
+requests. This number can be changed by setting the
+<code>max_keepalive</code> configuration value when starting an
+HTTP listener.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight 3.1.8
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="font-weight: bold"><span style="color: #000000">cowboy:start_http</span></span>(<span style="color: #FF6600">my_http_listener</span>, <span style="color: #993399">100</span>, [{<span style="color: #FF6600">port</span>, <span style="color: #993399">8080</span>}], [
+ {<span style="color: #FF6600">env</span>, [{<span style="color: #FF6600">dispatch</span>, <span style="color: #009900">Dispatch</span>}]},
+ {<span style="color: #FF6600">max_keepalive</span>, <span style="color: #993399">5</span>}
+])<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Cowboy implements the keep-alive mechanism by reusing
+the same process for all requests. This allows Cowboy
+to save memory. This works well because most code will
+not have any side effect impacting subsequent requests.
+But it also means you need to clean up if you do have
+code with side effects. The <code>terminate/3</code> function can
+be used for this purpose.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_pipelining_http_1_1">Pipelining (HTTP/1.1)</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>While HTTP is designed as a sequential protocol, with
+the client sending a request and then waiting for the
+response from the server, nothing prevents the client
+from sending more requests to the server without waiting
+for the response, due to how sockets work. The server
+still handles the requests sequentially and sends the
+responses in the same order.</p></div>
+<div class="paragraph"><p>This mechanism is called pipelining. It allows reducing
+latency when a client needs to request many resources
+at the same time. This is used by browsers when requesting
+static files for example.</p></div>
+<div class="paragraph"><p>This is handled automatically by the server.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_asynchronous_requests_http_2">Asynchronous requests (HTTP/2)</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>In HTTP/2, the client can send a request at any time.
+And the server can send a response at any time too.</p></div>
+<div class="paragraph"><p>This means for example that the client does not need
+to wait for a request to be fully sent to send another,
+it is possible to interleave a request with the request
+body of another request. The same is true with responses.
+Responses may also be sent in a different order.</p></div>
+<div class="paragraph"><p>Because requests and responses are fully asynchronous,
+Cowboy creates a new process for each request, and these
+processes are managed by another process that handles the
+connection itself.</p></div>
+<div class="paragraph"><p>HTTP/2 servers may also decide to send resources to the
+client before the client requests them. This is especially
+useful for sending static files associated with the HTML
+page requested, as this reduces the latency of the overall
+response. Cowboy does not support this particular mechanism
+at this point, however.</p></div>
+</div>
+</div>
+ + + +</div> + +<div class="span3 sidecol"> + + +<h3> + Cowboy + 2.0 + + User Guide +</h3> + +<ul> + + <li><a href="/docs/en/cowboy/2.0/guide">User Guide</a></li> + + + <li><a href="/docs/en/cowboy/2.0/manual">Function Reference</a></li> + + +</ul> + +<h4 id="docs-nav">Navigation</h4> + +<h4>Version select</h4> +<ul> + + + + <li><a href="/docs/en/cowboy/1.0/guide">1.0</a></li> + + <li><a href="/docs/en/cowboy/2.0/guide">2.0</a></li> + +</ul> + +</div> +</div> +</div> +</div> + + <footer> + <div class="container"> + <div class="row"> + <div class="span6"> + <p id="scroll-top"><a href="#">↑ Scroll to top</a></p> + <nav> + <ul> + <li><a href="mailto:[email protected]" title="Contact us">Contact us</a></li><li><a href="https://github.com/ninenines/ninenines.github.io" title="Github repository">Contribute to this site</a></li> + </ul> + </nav> + </div> + <div class="span6 credits"> + <p><img src="/img/footer_logo.png"></p> + <p>Copyright © Loïc Hoguin 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> + <script src="/js/bootstrap-carousel.js"></script> + <script src="/js/bootstrap-dropdown.js"></script> + <script src="/js/custom.js"></script> + </body> +</html> + + |