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<title>Nine Nines: cowboy_middleware(3)</title>
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<h1 class="lined-header"><span>cowboy_middleware(3)</span></h1>
<div class="sect1">
<h2 id="_name">Name</h2>
<div class="sectionbody">
<div class="paragraph"><p>cowboy_middleware - behaviour for middlewares</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_description">Description</h2>
<div class="sectionbody">
<div class="paragraph"><p>The <code>cowboy_middleware</code> behaviour defines the interface used
by Cowboy middleware modules.</p></div>
<div class="paragraph"><p>Middlewares process the request sequentially in the order they
are configured.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_types">Types</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_env_atom_any">env() = [{atom(), any()}]</h3>
<div class="paragraph"><p>The environment variable.</p></div>
<div class="paragraph"><p>One is created for every request. It is passed to each
middleware module executed and subsequently returned,
optionally with its contents modified.</p></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_callbacks">Callbacks</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_execute_req_env_8594_ok_req_env_suspend_module_function_args_stop_req">execute(Req, Env) → {ok, Req, Env} | {suspend, Module, Function, Args} | {stop, Req}</h3>
<div class="dlist"><dl>
<dt class="hdlist1">
Req = cowboy_req:req()
</dt>
<dd>
<p>
The Req object.
</p>
</dd>
<dt class="hdlist1">
Env = env()
</dt>
<dd>
<p>
The request environment.
</p>
</dd>
<dt class="hdlist1">
Module = module()
</dt>
<dd>
<p>
MFA to call when resuming the process.
</p>
</dd>
<dt class="hdlist1">
Function = atom()
</dt>
<dd>
<p>
MFA to call when resuming the process.
</p>
</dd>
<dt class="hdlist1">
Args = [any()]
</dt>
<dd>
<p>
MFA to call when resuming the process.
</p>
</dd>
</dl></div>
<div class="paragraph"><p>Execute the middleware.</p></div>
<div class="paragraph"><p>The <code>ok</code> return value indicates that everything went well
and that Cowboy should continue processing the request. A
response may or may not have been sent.</p></div>
<div class="paragraph"><p>The <code>suspend</code> return value will hibernate the process until
an Erlang message is received. Note that when resuming, any
previous stacktrace information will be gone.</p></div>
<div class="paragraph"><p>The <code>stop</code> return value stops Cowboy from doing any further
processing of the request, even if there are middlewares
that haven’t been executed yet. The connection may be left
open to receive more requests from the client.</p></div>
</div>
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<h3>
Cowboy
2.0
Function Reference
</h3>
<ul>
<li><a href="/docs/en/cowboy/2.0/guide">User Guide</a></li>
<li><a href="/docs/en/cowboy/2.0/manual">Function Reference</a></li>
</ul>
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<h4>Version select</h4>
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<li><a href="/docs/en/cowboy/1.0/manual">1.0</a></li>
<li><a href="/docs/en/cowboy/2.0/manual">2.0</a></li>
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