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diff --git a/docs/en/cowboy/2.4/guide/middlewares/index.html b/docs/en/cowboy/2.4/guide/middlewares/index.html new file mode 100644 index 00000000..28864e8c --- /dev/null +++ b/docs/en/cowboy/2.4/guide/middlewares/index.html @@ -0,0 +1,252 @@ +<!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 0.37.1" /> + + <title>Nine Nines: Middlewares</title> + + <link href='https://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic' rel='stylesheet' type='text/css'> + <link href="/css/99s.css?r=1" 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="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>Middlewares</span></h1> + +<div class="paragraph"><p>Cowboy delegates the request processing to middleware components. +By default, two middlewares are defined, for the routing and handling +of the request, as is detailed in most of this guide.</p></div> +<div class="paragraph"><p>Middlewares give you complete control over how requests are to be +processed. You can add your own middlewares to the mix or completely +change the chain of middlewares as needed.</p></div> +<div class="paragraph"><p>Cowboy will execute all middlewares in the given order, unless one +of them decides to stop processing.</p></div> +<div class="sect1"> +<h2 id="_usage">Usage</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Middlewares only need to implement a single callback: <code>execute/2</code>. +It is defined in the <code>cowboy_middleware</code> behavior.</p></div> +<div class="paragraph"><p>This callback has two arguments. The first is the <code>Req</code> object. +The second is the environment.</p></div> +<div class="paragraph"><p>Middlewares can return one of three different values:</p></div> +<div class="ulist"><ul> +<li> +<p> +<code>{ok, Req, Env}</code> to continue the request processing +</p> +</li> +<li> +<p> +<code>{suspend, Module, Function, Args}</code> to hibernate +</p> +</li> +<li> +<p> +<code>{stop, Req}</code> to stop processing and move on to the next request +</p> +</li> +</ul></div> +<div class="paragraph"><p>Of note is that when hibernating, processing will resume on the given +MFA, discarding all previous stacktrace. Make sure you keep the <code>Req</code> +and <code>Env</code> in the arguments of this MFA for later use.</p></div> +<div class="paragraph"><p>If an error happens during middleware processing, Cowboy will not try +to send an error back to the socket, the process will just crash. It +is up to the middleware to make sure that a reply is sent if something +goes wrong.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_configuration">Configuration</h2> +<div class="sectionbody"> +<div class="paragraph"><p>The middleware environment is defined as the <code>env</code> protocol option. +In the previous chapters we saw it briefly when we needed to pass +the routing information. It is a list of tuples with the first +element being an atom and the second any Erlang term.</p></div> +<div class="paragraph"><p>Two values in the environment are reserved:</p></div> +<div class="ulist"><ul> +<li> +<p> +<code>listener</code> contains the name of the listener +</p> +</li> +<li> +<p> +<code>result</code> contains the result of the processing +</p> +</li> +</ul></div> +<div class="paragraph"><p>The <code>listener</code> value is always defined. The <code>result</code> value can be +set by any middleware. If set to anything other than <code>ok</code>, Cowboy +will not process any subsequent requests on this connection.</p></div> +<div class="paragraph"><p>The middlewares that come with Cowboy may define or require other +environment values to perform.</p></div> +<div class="paragraph"><p>You can update the environment by calling the <code>cowboy:set_env/3</code> +convenience function, adding or replacing a value in the environment.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_routing_middleware">Routing middleware</h2> +<div class="sectionbody"> +<div class="paragraph"><p>The routing middleware requires the <code>dispatch</code> value. If routing +succeeds, it will put the handler name and options in the <code>handler</code> +and <code>handler_opts</code> values of the environment, respectively.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_handler_middleware">Handler middleware</h2> +<div class="sectionbody"> +<div class="paragraph"><p>The handler middleware requires the <code>handler</code> and <code>handler_opts</code> +values. It puts the result of the request handling into <code>result</code>.</p></div> +</div> +</div> + + + + + + + + + + + <nav style="margin:1em 0"> + + <a style="float:left" href="https://ninenines.eu/docs/en/cowboy/2.4/guide/streams/"> + Streams + </a> + + + + <a style="float:right" href="https://ninenines.eu/docs/en/cowboy/2.4/guide/migrating_from_2.3/"> + Migrating from Cowboy 2.3 to 2.4 + </a> + + </nav> + + + + +</div> + +<div class="span3 sidecol"> + + +<h3> + Cowboy + 2.4 + + User Guide +</h3> + +<ul> + + <li><a href="/docs/en/cowboy/2.4/guide">User Guide</a></li> + + + <li><a href="/docs/en/cowboy/2.4/manual">Function Reference</a></li> + + +</ul> + +<h4 id="docs-nav">Navigation</h4> + +<h4>Version select</h4> +<ul> + + + + <li><a href="/docs/en/cowboy/2.4/guide">2.4</a></li> + + <li><a href="/docs/en/cowboy/2.3/guide">2.3</a></li> + + <li><a href="/docs/en/cowboy/2.2/guide">2.2</a></li> + + <li><a href="/docs/en/cowboy/2.1/guide">2.1</a></li> + + <li><a href="/docs/en/cowboy/2.0/guide">2.0</a></li> + + <li><a href="/docs/en/cowboy/1.0/guide">1.0</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 2012-2018</p> + </div> + </div> + </div> + </footer> + + + <script src="/js/custom.js"></script> + </body> +</html> + + |