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| author | Loïc Hoguin <[email protected]> | 2018-04-04 13:13:37 +0200 |
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| committer | Loïc Hoguin <[email protected]> | 2018-04-04 13:13:37 +0200 |
| commit | d2a3f2cedd7c00d0933222aed9c06b3149aa4db4 (patch) | |
| tree | 4f1499bac639c782b250af0fbf0dec2064315813 /docs/en/cowboy/2.3/guide/resource_design/index.html | |
| parent | 1d654719f5fa6be67d2c95145872068665702cb7 (diff) | |
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Cowboy 2.3.0
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diff --git a/docs/en/cowboy/2.3/guide/resource_design/index.html b/docs/en/cowboy/2.3/guide/resource_design/index.html new file mode 100644 index 00000000..e5b4cea8 --- /dev/null +++ b/docs/en/cowboy/2.3/guide/resource_design/index.html @@ -0,0 +1,374 @@ +<!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: Designing a resource handler</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>Designing a resource handler</span></h1> + +<div class="paragraph"><p>This chapter aims to provide you with a list of questions +you must answer in order to write a good resource handler. +It is meant to be usable as a step by step guide.</p></div> +<div class="sect1"> +<h2 id="_the_service">The service</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Can the service become unavailable, and when it does, can +we detect it? For example, database connectivity problems +may be detected early. We may also have planned outages +of all or parts of the system. Implement the +<code>service_available</code> callback.</p></div> +<div class="paragraph"><p>What HTTP methods does the service implement? Do we need +more than the standard OPTIONS, HEAD, GET, PUT, POST, +PATCH and DELETE? Are we not using one of those at all? +Implement the <code>known_methods</code> callback.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_type_of_resource_handler">Type of resource handler</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Am I writing a handler for a collection of resources, +or for a single resource?</p></div> +<div class="paragraph"><p>The semantics for each of these are quite different. +You should not mix collection and single resource in +the same handler.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_collection_handler">Collection handler</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Skip this section if you are not doing a collection.</p></div> +<div class="paragraph"><p>Is the collection hardcoded or dynamic? For example, +if you use the route <code>/users</code> for the collection of +users then the collection is hardcoded; if you use +<code>/forums/:category</code> for the collection of threads +then it isn’t. When the collection is hardcoded you +can safely assume the resource always exists.</p></div> +<div class="paragraph"><p>What methods should I implement?</p></div> +<div class="paragraph"><p>OPTIONS is used to get some information about the +collection. It is recommended to allow it even if you +do not implement it, as Cowboy has a default +implementation built-in.</p></div> +<div class="paragraph"><p>HEAD and GET are used to retrieve the collection. +If you allow GET, also allow HEAD as there’s no extra +work required to make it work.</p></div> +<div class="paragraph"><p>POST is used to create a new resource inside the +collection. Creating a resource by using POST on +the collection is useful when resources may be +created before knowing their URI, usually because +parts of it are generated dynamically. A common +case is some kind of auto incremented integer +identifier.</p></div> +<div class="paragraph"><p>The next methods are more rarely allowed.</p></div> +<div class="paragraph"><p>PUT is used to create a new collection (when +the collection isn’t hardcoded), or replace +the entire collection.</p></div> +<div class="paragraph"><p>DELETE is used to delete the entire collection.</p></div> +<div class="paragraph"><p>PATCH is used to modify the collection using +instructions given in the request body. A PATCH +operation is atomic. The PATCH operation may +be used for such things as reordering; adding, +modifying or deleting parts of the collection.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_single_resource_handler">Single resource handler</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Skip this section if you are doing a collection.</p></div> +<div class="paragraph"><p>What methods should I implement?</p></div> +<div class="paragraph"><p>OPTIONS is used to get some information about the +resource. It is recommended to allow it even if you +do not implement it, as Cowboy has a default +implementation built-in.</p></div> +<div class="paragraph"><p>HEAD and GET are used to retrieve the resource. +If you allow GET, also allow HEAD as there’s no extra +work required to make it work.</p></div> +<div class="paragraph"><p>POST is used to update the resource.</p></div> +<div class="paragraph"><p>PUT is used to create a new resource (when it doesn’t +already exist) or replace the resource.</p></div> +<div class="paragraph"><p>DELETE is used to delete the resource.</p></div> +<div class="paragraph"><p>PATCH is used to modify the resource using +instructions given in the request body. A PATCH +operation is atomic. The PATCH operation may +be used for adding, removing or modifying specific +values in the resource.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_the_resource">The resource</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Following the above discussion, implement the +<code>allowed_methods</code> callback.</p></div> +<div class="paragraph"><p>Does the resource always exist? If it may not, implement +the <code>resource_exists</code> callback.</p></div> +<div class="paragraph"><p>Do I need to authenticate the client before they can +access the resource? What authentication mechanisms +should I provide? This may include form-based, token-based +(in the URL or a cookie), HTTP basic, HTTP digest, +SSL certificate or any other form of authentication. +Implement the <code>is_authorized</code> callback.</p></div> +<div class="paragraph"><p>Do I need fine-grained access control? How do I determine +that they are authorized access? Handle that in your +<code>is_authorized</code> callback.</p></div> +<div class="paragraph"><p>Can access to a resource be forbidden regardless of access +being authorized? A simple example of that is censorship +of a resource. Implement the <code>forbidden</code> callback.</p></div> +<div class="paragraph"><p>Are there any constraints on the length of the resource URI? +For example, the URI may be used as a key in storage and may +have a limit in length. Implement <code>uri_too_long</code>.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_representations">Representations</h2> +<div class="sectionbody"> +<div class="paragraph"><p>What media types do I provide? If text based, what charsets +are provided? What languages do I provide?</p></div> +<div class="paragraph"><p>Implement the mandatory <code>content_types_provided</code>. Prefix +the callbacks with <code>to_</code> for clarity. For example, <code>to_html</code> +or <code>to_text</code>.</p></div> +<div class="paragraph"><p>Implement the <code>languages_provided</code> or <code>charsets_provided</code> +callbacks if applicable.</p></div> +<div class="paragraph"><p>Is there any other header that may make the representation +of the resource vary? Implement the <code>variances</code> callback.</p></div> +<div class="paragraph"><p>Depending on your choices for caching content, you may +want to implement one or more of the <code>generate_etag</code>, +<code>last_modified</code> and <code>expires</code> callbacks.</p></div> +<div class="paragraph"><p>Do I want the user or user agent to actively choose a +representation available? Send a list of available +representations in the response body and implement +the <code>multiple_choices</code> callback.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_redirections">Redirections</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Do I need to keep track of what resources were deleted? +For example, you may have a mechanism where moving a +resource leaves a redirect link to its new location. +Implement the <code>previously_existed</code> callback.</p></div> +<div class="paragraph"><p>Was the resource moved, and is the move temporary? If +it is explicitly temporary, for example due to maintenance, +implement the <code>moved_temporarily</code> callback. Otherwise, +implement the <code>moved_permanently</code> callback.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_the_request">The request</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Do you need to read the query string? Individual headers? +Implement <code>malformed_request</code> and do all the parsing and +validation in this function. Note that the body should not +be read at this point.</p></div> +<div class="paragraph"><p>May there be a request body? Will I know its size? +What’s the maximum size of the request body I’m willing +to accept? Implement <code>valid_entity_length</code>.</p></div> +<div class="paragraph"><p>Finally, take a look at the sections corresponding to the +methods you are implementing.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_options_method">OPTIONS method</h2> +<div class="sectionbody"> +<div class="paragraph"><p>Cowboy by default will send back a list of allowed methods. +Do I need to add more information to the response? Implement +the <code>options</code> 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>If you implement the methods GET and/or HEAD, you must +implement one <code>ProvideResource</code> callback for each +content-type returned by the <code>content_types_provided</code> +callback.</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>If you implement the methods PUT, POST and/or PATCH, +you must implement the <code>content_types_accepted</code> callback, +and one <code>AcceptCallback</code> callback for each content-type +it returns. Prefix the <code>AcceptCallback</code> callback names +with <code>from_</code> for clarity. For example, <code>from_html</code> or +<code>from_json</code>.</p></div> +<div class="paragraph"><p>Do we want to allow the POST method to create individual +resources directly through their URI (like PUT)? Implement +the <code>allow_missing_post</code> callback. It is recommended to +explicitly use PUT in these cases instead.</p></div> +<div class="paragraph"><p>May there be conflicts when using PUT to create or replace +a resource? Do we want to make sure that two updates around +the same time are not cancelling one another? Implement the +<code>is_conflict</code> callback.</p></div> +</div> +</div> +<div class="sect1"> +<h2 id="_delete_methods">DELETE methods</h2> +<div class="sectionbody"> +<div class="paragraph"><p>If you implement the method DELETE, you must implement +the <code>delete_resource</code> callback.</p></div> +<div class="paragraph"><p>When <code>delete_resource</code> returns, is the resource completely +removed from the server, including from any caching service? +If not, and/or if the deletion is asynchronous and we have +no way of knowing it has been completed yet, implement the +<code>delete_completed</code> callback.</p></div> +</div> +</div> + + + + + + + + + + + <nav style="margin:1em 0"> + + <a style="float:left" href="https://ninenines.eu/docs/en/cowboy/2.3/guide/rest_flowcharts/"> + REST flowcharts + </a> + + + + <a style="float:right" href="https://ninenines.eu/docs/en/cowboy/2.3/guide/ws_protocol/"> + The Websocket protocol + </a> + + </nav> + + + + +</div> + +<div class="span3 sidecol"> + + +<h3> + Cowboy + 2.3 + + User Guide +</h3> + +<ul> + + <li><a href="/docs/en/cowboy/2.3/guide">User Guide</a></li> + + + <li><a href="/docs/en/cowboy/2.3/manual">Function Reference</a></li> + + +</ul> + +<h4 id="docs-nav">Navigation</h4> + +<h4>Version select</h4> +<ul> + + + + <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 2012-2016</p> + </div> + </div> + </div> + </footer> + + + <script src="/js/custom.js"></script> + </body> +</html> + + |