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diff --git a/docs/en/cowboy/2.1/guide/rest_flowcharts/index.html b/docs/en/cowboy/2.1/guide/rest_flowcharts/index.html new file mode 100644 index 00000000..eadfcc74 --- /dev/null +++ b/docs/en/cowboy/2.1/guide/rest_flowcharts/index.html @@ -0,0 +1,401 @@ +<!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 0.30.2" /> + + <title>Nine Nines: REST flowcharts</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="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>REST flowcharts</span></h1> + +<div class="paragraph"><p>This chapter will explain the REST handler state machine through +a number of different diagrams.</p></div> +<div class="paragraph"><p>There are four main paths that requests may follow. One for the +method OPTIONS; one for the methods GET and HEAD; one for the +methods PUT, POST and PATCH; and one for the method DELETE.</p></div> +<div class="paragraph"><p>All paths start with the "Start" diagram, and all paths excluding +the OPTIONS path go through the "Content negotiation" diagram +and optionally the "Conditional requests" diagram if the resource +exists.</p></div> +<div class="paragraph"><p>The red squares refer to another diagram. The light green squares +indicate a response. Other squares may be either a callback or a +question answered by Cowboy itself. Green arrows tend to indicate +the default behavior if the callback is undefined.</p></div> +<div class="sect1"> +<h2 id="_start">Start</h2> +<div class="sectionbody"> +<div class="paragraph"><p>All requests start from here.</p></div> +<div class="imageblock"> +<div class="content"> +<img src="../rest_start.png" alt="REST starting flowchart" /> +</div> +</div> +<div class="paragraph"><p>A series of callbacks are called in succession to perform +a general checkup of the service, the request line and +request headers.</p></div> +<div class="paragraph"><p>The request body, if any, is not expected to have been +received for any of these steps. It is only processed +at the end of the "PUT, POST and PATCH methods" diagram, +when all conditions have been met.</p></div> +<div class="paragraph"><p>The <code>known_methods</code> and <code>allowed_methods</code> callbacks +return a list of methods. Cowboy then checks if the request +method is in the list, and stops otherwise.</p></div> +<div class="paragraph"><p>The <code>is_authorized</code> callback may be used to check that +access to the resource is authorized. Authentication +may also be performed as needed. When authorization is +denied, the return value from the callback must include +a challenge applicable to the requested resource, which +will be sent back to the client in the www-authenticate +header.</p></div> +<div class="paragraph"><p>This diagram is immediately followed by either the +"OPTIONS method" diagram when the request method is +OPTIONS, or the "Content negotiation" diagram otherwise.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_options_method">OPTIONS method</h2> +<div class="sectionbody"> +<div class="paragraph"><p>This diagram only applies to OPTIONS requests.</p></div> +<div class="imageblock"> +<div class="content"> +<img src="../rest_options.png" alt="REST OPTIONS method flowchart" /> +</div> +</div> +<div class="paragraph"><p>The <code>options</code> callback may be used to add information +about the resource, such as media types or languages +provided; allowed methods; any extra information. A +response body may also be set, although clients should +not be expected to read it.</p></div> +<div class="paragraph"><p>If the <code>options</code> callback is not defined, Cowboy will +send a response containing the list of allowed methods +by default.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_content_negotiation">Content negotiation</h2> +<div class="sectionbody"> +<div class="paragraph"><p>This diagram applies to all request methods other than +OPTIONS. It is executed right after the "Start" diagram +is completed.</p></div> +<div class="imageblock"> +<div class="content"> +<img src="../rest_conneg.png" alt="REST content negotiation flowchart" /> +</div> +</div> +<div class="paragraph"><p>The purpose of these steps is to determine an appropriate +representation to be sent back to the client.</p></div> +<div class="paragraph"><p>The request may contain any of the accept header; the +accept-language header; or the accept-charset header. +When present, Cowboy will parse the headers and then +call the corresponding callback to obtain the list +of provided content-type, language or charset for this +resource. It then automatically select the best match +based on the request.</p></div> +<div class="paragraph"><p>If a callback is not defined, Cowboy will select the +content-type, language or charset that the client +prefers.</p></div> +<div class="paragraph"><p>The <code>content_types_provided</code> also returns the name of +a callback for every content-type it accepts. This +callback will only be called at the end of the +"GET and HEAD methods" diagram, when all conditions +have been met.</p></div> +<div class="paragraph"><p>The selected content-type, language and charset are +saved as meta values in the Req object. You <strong>should</strong> +use the appropriate representation if you set a +response body manually (alongside an error code, +for example).</p></div> +<div class="paragraph"><p>This diagram is immediately followed by +the "GET and HEAD methods" diagram, +the "PUT, POST and PATCH methods" diagram, +or the "DELETE method" diagram, depending on the +method.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_get_and_head_methods">GET and HEAD methods</h2> +<div class="sectionbody"> +<div class="paragraph"><p>This diagram only applies to GET and HEAD requests.</p></div> +<div class="paragraph"><p>For a description of the <code>cond</code> step, please see +the "Conditional requests" diagram.</p></div> +<div class="imageblock"> +<div class="content"> +<img src="../rest_get_head.png" alt="REST GET/HEAD methods flowchart" /> +</div> +</div> +<div class="paragraph"><p>When the resource exists, and the conditional steps +succeed, the resource can be retrieved.</p></div> +<div class="paragraph"><p>Cowboy prepares the response by first retrieving +metadata about the representation, then by calling +the <code>ProvideResource</code> callback. This is the callback +you defined for each content-types you returned from +<code>content_types_provided</code>. This callback returns the body +that will be sent back to the client, or a fun if the +body must be streamed.</p></div> +<div class="paragraph"><p>When the resource does not exist, Cowboy will figure out +whether the resource existed previously, and if so whether +it was moved elsewhere in order to redirect the client to +the new URI.</p></div> +<div class="paragraph"><p>The <code>moved_permanently</code> and <code>moved_temporarily</code> callbacks +must return the new location of the resource if it was in +fact moved.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_put_post_and_patch_methods">PUT, POST and PATCH methods</h2> +<div class="sectionbody"> +<div class="paragraph"><p>This diagram only applies to PUT, POST and PATCH requests.</p></div> +<div class="paragraph"><p>For a description of the <code>cond</code> step, please see +the "Conditional requests" diagram.</p></div> +<div class="imageblock"> +<div class="content"> +<img src="../rest_put_post_patch.png" alt="REST PUT/POST/PATCH methods flowchart" /> +</div> +</div> +<div class="paragraph"><p>When the resource exists, first the conditional steps +are executed. When that succeeds, and the method is PUT, +Cowboy will call the <code>is_conflict</code> callback. This function +can be used to prevent potential race conditions, by locking +the resource for example.</p></div> +<div class="paragraph"><p>Then all three methods reach the <code>content_types_accepted</code> +step that we will describe in a few paragraphs.</p></div> +<div class="paragraph"><p>When the resource does not exist, and the method is PUT, +Cowboy will check for conflicts and then move on to the +<code>content_types_accepted</code> step. For other methods, Cowboy +will figure out whether the resource existed previously, +and if so whether it was moved elsewhere. If the resource +is truly non-existent, the method is POST and the call +for <code>allow_missing_post</code> returns <code>true</code>, then Cowboy will +move on to the <code>content_types_accepted</code> step. Otherwise +the request processing ends there.</p></div> +<div class="paragraph"><p>The <code>moved_permanently</code> and <code>moved_temporarily</code> callbacks +must return the new location of the resource if it was in +fact moved.</p></div> +<div class="paragraph"><p>The <code>content_types_accepted</code> returns a list of +content-types it accepts, but also the name of a callback +for each of them. Cowboy will select the appropriate +callback for processing the request body and call it.</p></div> +<div class="paragraph"><p>This callback may return one of three different return +values.</p></div> +<div class="paragraph"><p>If an error occurred while processing the request body, +it must return <code>false</code> and Cowboy will send an +appropriate error response.</p></div> +<div class="paragraph"><p>If the method is POST, then you may return <code>true</code> with +an URI of where the resource has been created. This is +especially useful for writing handlers for collections.</p></div> +<div class="paragraph"><p>Otherwise, return <code>true</code> to indicate success. Cowboy +will select the appropriate response to be sent depending +on whether a resource has been created, rather than +modified, and on the availability of a location header +or a body in the response.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_delete_method">DELETE method</h2> +<div class="sectionbody"> +<div class="paragraph"><p>This diagram only applies to DELETE requests.</p></div> +<div class="paragraph"><p>For a description of the <code>cond</code> step, please see +the "Conditional requests" diagram.</p></div> +<div class="imageblock"> +<div class="content"> +<img src="../rest_delete.png" alt="REST DELETE method flowchart" /> +</div> +</div> +<div class="paragraph"><p>When the resource exists, and the conditional steps +succeed, the resource can be deleted.</p></div> +<div class="paragraph"><p>Deleting the resource is a two steps process. First +the callback <code>delete_resource</code> is executed. Use this +callback to delete the resource.</p></div> +<div class="paragraph"><p>Because the resource may be cached, you must also +delete all cached representations of this resource +in the system. This operation may take a while though, +so you may return before it finished.</p></div> +<div class="paragraph"><p>Cowboy will then call the <code>delete_completed</code> callback. +If you know that the resource has been completely +deleted from your system, including from caches, then +you can return <code>true</code>. If any doubts persist, return +<code>false</code>. Cowboy will assume <code>true</code> by default.</p></div> +<div class="paragraph"><p>To finish, Cowboy checks if you set a response body, +and depending on that, sends the appropriate response.</p></div> +<div class="paragraph"><p>When the resource does not exist, Cowboy will figure out +whether the resource existed previously, and if so whether +it was moved elsewhere in order to redirect the client to +the new URI.</p></div> +<div class="paragraph"><p>The <code>moved_permanently</code> and <code>moved_temporarily</code> callbacks +must return the new location of the resource if it was in +fact moved.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_conditional_requests">Conditional requests</h2> +<div class="sectionbody"> +<div class="paragraph"><p>This diagram applies to all request methods other than +OPTIONS. It is executed right after the <code>resource_exists</code> +callback, when the resource exists.</p></div> +<div class="imageblock"> +<div class="content"> +<img src="../rest_cond.png" alt="REST conditional requests flowchart" /> +</div> +</div> +<div class="paragraph"><p>A request becomes conditional when it includes either of +the if-match header; the if-unmodified-since header; the +if-none-match header; or the if-modified-since header.</p></div> +<div class="paragraph"><p>If the condition fails, the request ends immediately +without any retrieval or modification of the resource.</p></div> +<div class="paragraph"><p>The <code>generate_etag</code> and <code>last_modified</code> are called as +needed. Cowboy will only call them once and then cache +the results for subsequent use.</p></div> +</div> +</div> + + + + + + + + + + + <nav style="margin:1em 0"> + + <a style="float:left" href="https://ninenines.eu/docs/en/cowboy/2.1/guide/rest_handlers/"> + REST handlers + </a> + + + + <a style="float:right" href="https://ninenines.eu/docs/en/cowboy/2.1/guide/resource_design/"> + Designing a resource handler + </a> + + </nav> + + + + +</div> + +<div class="span3 sidecol"> + + +<h3> + Cowboy + 2.1 + + User Guide +</h3> + +<ul> + + <li><a href="/docs/en/cowboy/2.1/guide">User Guide</a></li> + + + <li><a href="/docs/en/cowboy/2.1/manual">Function Reference</a></li> + + +</ul> + +<h4 id="docs-nav">Navigation</h4> + +<h4>Version select</h4> +<ul> + + + + <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 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="/js/custom.js"></script> + </body> +</html> + + |