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<title>Nine Nines: Embedded mode</title>
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<h1 class="lined-header"><span>Embedded mode</span></h1>
<div class="paragraph"><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></div>
<div class="sect1">
<h2 id="_embedding">Embedding</h2>
<div class="sectionbody">
<div class="paragraph"><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></div>
<div class="paragraph"><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></div>
<div class="paragraph"><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></div>
<div class="paragraph"><p>As for <code>ranch_sup</code>, the child spec is simple enough to not require a
convenience function.</p></div>
<div class="paragraph"><p>The following example adds both <code>ranch_sup</code> and one listener to another
application’s supervision tree.</p></div>
<div class="listingblock">
<div class="title">Embed Ranch directly in your supervision tree</div>
<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: #990000">-></span>
<span style="color: #009900">RanchSupSpec</span> <span style="color: #990000">=</span> {<span style="color: #FF6600">ranch_sup</span>, {<span style="color: #FF6600">ranch_sup</span>, <span style="color: #FF6600">start_link</span>, []},
<span style="color: #FF6600">permanent</span>, <span style="color: #993399">5000</span>, <span style="color: #FF6600">supervisor</span>, [<span style="color: #FF6600">ranch_sup</span>]},
<span style="color: #009900">ListenerSpec</span> <span style="color: #990000">=</span> <span style="font-weight: bold"><span style="color: #000000">ranch:child_spec</span></span>(<span style="color: #FF6600">echo</span>, <span style="color: #993399">100</span>,
<span style="color: #FF6600">ranch_tcp</span>, [{<span style="color: #FF6600">port</span>, <span style="color: #993399">5555</span>}],
<span style="color: #FF6600">echo_protocol</span>, []
),
{<span style="color: #FF6600">ok</span>, {{<span style="color: #FF6600">one_for_one</span>, <span style="color: #993399">10</span>, <span style="color: #993399">10</span>}, [<span style="color: #009900">RanchSupSpec</span>, <span style="color: #009900">ListenerSpec</span>]}}<span style="color: #990000">.</span></tt></pre></div></div>
<div class="paragraph"><p>Remember, you can add as many listener child specs as needed, but only
one <code>ranch_sup</code> spec!</p></div>
<div class="paragraph"><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></div>
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<h3>
Ranch
1.4
User Guide
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<h4>Version select</h4>
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<li><a href="/docs/en/ranch/1.4/guide">1.4</a></li>
<li><a href="/docs/en/ranch/1.3/guide">1.3</a></li>
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