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<h1 class="lined-header"><span>Embedded mode</span></h1>
<p>Embedded mode allows you to insert Ranch listeners directly in your supervision tree. This allows for greater fault tolerance control by permitting the shutdown of a listener due to the failure of another part of the application and vice versa.</p>
<h2 id="_embedding">Embedding</h2>
<p>To embed Ranch in your application you can simply add the child specs to your supervision tree. This can all be done in the <code>init/1</code> function of one of your application supervisors.</p>
<p>Ranch requires at the minimum two kinds of child specs for embedding. First, you need to add <code>ranch_sup</code> to your supervision tree, only once, regardless of the number of listeners you will use. Then you need to add the child specs for each listener.</p>
<p>Ranch has a convenience function for getting the listeners child specs called <code>ranch:child_spec/5</code>, that works like <code>ranch:start_listener/5</code>, except that it doesn't start anything, it only returns child specs.</p>
<p>As for <code>ranch_sup</code>, the child spec is simple enough to not require a convenience function.</p>
<p>The following example adds both <code>ranch_sup</code> and one listener to another application's supervision tree.</p>
<div class="listingblock"><div class="title">Embed Ranch directly in your supervision tree</div>
<div class="content"><!-- Generator: GNU source-highlight 3.1.9
by Lorenzo Bettini
http://www.lorenzobettini.it
http://www.gnu.org/software/src-highlite -->
<pre><tt><b><font color="#000000">init</font></b>([]) <font color="#990000">-></font>
<font color="#009900">RanchSupSpec</font> <font color="#990000">=</font> {<font color="#FF6600">ranch_sup</font>, {<font color="#FF6600">ranch_sup</font>, <font color="#FF6600">start_link</font>, []},
<font color="#FF6600">permanent</font>, <font color="#993399">5000</font>, <font color="#FF6600">supervisor</font>, [<font color="#FF6600">ranch_sup</font>]},
<font color="#009900">ListenerSpec</font> <font color="#990000">=</font> <b><font color="#000000">ranch:child_spec</font></b>(<font color="#FF6600">echo</font>, <font color="#993399">100</font>,
<font color="#FF6600">ranch_tcp</font>, [{<font color="#FF6600">port</font>, <font color="#993399">5555</font>}],
<font color="#FF6600">echo_protocol</font>, []
),
{<font color="#FF6600">ok</font>, {{<font color="#FF6600">one_for_one</font>, <font color="#993399">10</font>, <font color="#993399">10</font>}, [<font color="#009900">RanchSupSpec</font>, <font color="#009900">ListenerSpec</font>]}}<font color="#990000">.</font></tt></pre>
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<p>Remember, you can add as many listener child specs as needed, but only one <code>ranch_sup</code> spec!</p>
<p>It is recommended that your architecture makes sure that all listeners are restarted if <code>ranch_sup</code> fails. See the Ranch internals chapter for more details on how Ranch does it.</p>
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