Cowboy 2.4.0

author: Loïc Hoguin <[email protected]> 2018-05-02 11:35:26 +0200
committer: Loïc Hoguin <[email protected]> 2018-05-02 11:35:26 +0200
commit: fec98300ec9af6c8b5f3120a60f217983c451076 (patch)
tree: 9772977293124e8b9b5b253e44d8c2695cddfb44 /docs/en/cowboy/2.4/guide/getting_started/index.html
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+
+<h1 class="lined-header"><span>Getting started</span></h1>
+
+<div class="paragraph"><p>Erlang is more than a language, it is also an operating system
+for your applications. Erlang developers rarely write standalone
+modules, they write libraries or applications, and then bundle
+those into what is called a release. A release contains the
+Erlang VM plus all applications required to run the node, so
+it can be pushed to production directly.</p></div>
+<div class="paragraph"><p>This chapter walks you through all the steps of setting up
+Cowboy, writing your first application and generating your first
+release. At the end of this chapter you should know everything
+you need to push your first Cowboy application to production.</p></div>
+<div class="sect1">
+<h2 id="_prerequisites">Prerequisites</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>We are going to use the <a href="https://github.com/ninenines/erlang.mk">Erlang.mk</a>
+build system. If you are using Windows, please check the
+<a href="http://erlang.mk/guide/installation.html">Installation instructions</a>
+to get your environment setup before you continue.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_bootstrap">Bootstrap</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>First, let&#8217;s create the directory for our application.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>$ mkdir hello_erlang
+$ cd hello_erlang</tt></pre></div></div>
+<div class="paragraph"><p>Then we need to download Erlang.mk. Either use the following
+command or download it manually.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>$ wget https<span style="color: #990000">:</span>//erlang<span style="color: #990000">.</span>mk/erlang<span style="color: #990000">.</span>mk</tt></pre></div></div>
+<div class="paragraph"><p>We can now bootstrap our application. Since we are going to generate
+a release, we will also bootstrap it at the same time.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>$ make -f erlang<span style="color: #990000">.</span>mk bootstrap bootstrap-rel</tt></pre></div></div>
+<div class="paragraph"><p>This creates a Makefile, a base application, and the release files
+necessary for creating the release. We can already build and start
+this release.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>$ make run
+<span style="color: #990000">...</span>
+<span style="color: #990000">(</span>hello_erlang@<span style="color: #993399">127.0</span><span style="color: #990000">.</span><span style="color: #993399">0.1</span><span style="color: #990000">)</span><span style="color: #993399">1</span><span style="color: #990000">&gt;</span></tt></pre></div></div>
+<div class="paragraph"><p>Entering the command <code>i().</code> will show the running processes, including
+one called <code>hello_erlang_sup</code>. This is the supervisor for our
+application.</p></div>
+<div class="paragraph"><p>The release currently does nothing. In the rest of this chapter we
+will add Cowboy as a dependency and write a simple "Hello world!"
+handler.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_cowboy_setup">Cowboy setup</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>We will modify the <em>Makefile</em> to tell the build system it needs to
+fetch and compile Cowboy:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt><span style="color: #009900">PROJECT =</span> hello_erlang
+
+<span style="color: #009900">DEPS =</span> cowboy
+<span style="color: #009900">dep_cowboy_commit =</span> 2.4.0
+
+<span style="color: #009900">DEP_PLUGINS =</span> cowboy
+
+include erlang.mk</tt></pre></div></div>
+<div class="paragraph"><p>We also tell the build system to load the plugins Cowboy provides.
+These include predefined templates that we will use soon.</p></div>
+<div class="paragraph"><p>If you do <code>make run</code> now, Cowboy will be included in the release
+and started automatically. This is not enough however, as Cowboy
+doesn&#8217;t do anything by default. We still need to tell Cowboy to
+listen for connections.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_listening_for_connections">Listening for connections</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>First we define the routes that Cowboy will use to map requests
+to handler modules, and then we start the listener. This is best
+done at application startup.</p></div>
+<div class="paragraph"><p>Open the <em>src/hello_erlang_app.erl</em> file and add the necessary
+code to the <code>start/2</code> function to make it look like this:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight
+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">start</span></span>(<span style="color: #009900">_Type</span>, <span style="color: #009900">_Args</span>) <span style="color: #990000">-&gt;</span>
+    <span style="color: #009900">Dispatch</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy_router:compile</span></span>([
+        {<span style="color: #FF6600">'_'</span>, [{<span style="color: #FF0000">"/"</span>, <span style="color: #FF6600">hello_handler</span>, []}]}
+    ]),
+    {<span style="color: #FF6600">ok</span>, <span style="color: #990000">_</span>} <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">cowboy:start_clear</span></span>(<span style="color: #FF6600">my_http_listener</span>,
+        [{<span style="color: #FF6600">port</span>, <span style="color: #993399">8080</span>}],
+        #{<span style="color: #0000FF">env</span> <span style="color: #990000">=&gt;</span> #{<span style="color: #0000FF">dispatch</span> <span style="color: #990000">=&gt;</span> <span style="color: #009900">Dispatch</span>}}
+    ),
+    <span style="font-weight: bold"><span style="color: #000000">hello_erlang_sup:start_link</span></span>()<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>Routes are explained in details in the <a href="../routing">Routing</a>
+chapter. For this tutorial we map the path <code>/</code> to the handler
+module <code>hello_handler</code>. This module doesn&#8217;t exist yet.</p></div>
+<div class="paragraph"><p>Build and start the release, then open <a href="http://localhost:8080">http://localhost:8080</a>
+in your browser. You will get a 500 error because the module is missing.
+Any other URL, like <a href="http://localhost:8080/test">http://localhost:8080/test</a>, will result in a
+404 error.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_handling_requests">Handling requests</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Cowboy features different kinds of handlers, including REST
+and Websocket handlers. For this tutorial we will use a plain
+HTTP handler.</p></div>
+<div class="paragraph"><p>Generate a handler from a template:</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight
+by Lorenzo Bettini
+http://www.lorenzobettini.it
+http://www.gnu.org/software/src-highlite -->
+<pre><tt>$ make new <span style="color: #009900">t</span><span style="color: #990000">=</span>cowboy<span style="color: #990000">.</span>http <span style="color: #009900">n</span><span style="color: #990000">=</span>hello_handler</tt></pre></div></div>
+<div class="paragraph"><p>Then, open the <em>src/hello_handler.erl</em> file and modify
+the <code>init/2</code> function like this to send a reply.</p></div>
+<div class="listingblock">
+<div class="content"><!-- Generator: GNU source-highlight
+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">init</span></span>(<span style="color: #009900">Req0</span>, <span style="color: #009900">State</span>) <span style="color: #990000">-&gt;</span>
+    <span style="color: #009900">Req</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">&lt;&lt;</span><span style="color: #FF0000">"content-type"</span><span style="color: #990000">&gt;&gt;</span> <span style="color: #990000">=&gt;</span> <span style="color: #990000">&lt;&lt;</span><span style="color: #FF0000">"text/plain"</span><span style="color: #990000">&gt;&gt;</span>},
+        <span style="color: #990000">&lt;&lt;</span><span style="color: #FF0000">"Hello Erlang!"</span><span style="color: #990000">&gt;&gt;</span>,
+        <span style="color: #009900">Req0</span>),
+    {<span style="color: #FF6600">ok</span>, <span style="color: #009900">Req</span>, <span style="color: #009900">State</span>}<span style="color: #990000">.</span></tt></pre></div></div>
+<div class="paragraph"><p>What the above code does is send a 200 OK reply, with the
+Content-type header set to <code>text/plain</code> and the response
+body set to <code>Hello Erlang!</code>.</p></div>
+<div class="paragraph"><p>If you run the release and open <a href="http://localhost:8080">http://localhost:8080</a>
+in your browser, you should get a nice <code>Hello Erlang!</code> displayed!</p></div>
+</div>
+</div>
+
+
+
+	
+		
+		
+		
+		
+		
+
+		<nav style="margin:1em 0">
+			
+				<a style="float:left" href="https://ninenines.eu/docs/en/cowboy/2.4/guide/introduction/">
+					Introduction
+				</a>
+			
+
+			
+				<a style="float:right" href="https://ninenines.eu/docs/en/cowboy/2.4/guide/flow_diagram/">
+					Flow diagram
+				</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>
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author	Loïc Hoguin <[email protected]>	2018-05-02 11:35:26 +0200
committer	Loïc Hoguin <[email protected]>	2018-05-02 11:35:26 +0200
commit	fec98300ec9af6c8b5f3120a60f217983c451076 (patch)
tree	9772977293124e8b9b5b253e44d8c2695cddfb44 /docs/en/cowboy/2.4/guide/getting_started/index.html
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