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<h1>
<small class="visible-xs">poa_backend v0.1.0</small>
POABackend.Receiver <small>behaviour</small>
<a href="https://github.com/poanetwork/poa-netstats-wharehouse/blob/v0.1.0/lib/poa_backend/receiver.ex#L1" title="View Source" class="view-source" rel="help">
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</h1>
<section id="moduledoc">
<p>Defines a Receiver Plugin.</p>
<p>A Receiver plugin will run in an independent process and will run the <code class="inline">metrics_received/3</code>
function every time it receives a metric from the agents.</p>
<p><a href="POABackend.html"><code class="inline">POABackend</code></a> app reads the Receivers configuration from the <code class="inline">config.exs</code> file when bootstrap and will create a
process per each one of them. That configuration is referenced by :receivers key.</p>
<pre><code class="elixir">config :poa_backend,
:receivers,
[
{name, module, args}
]</code></pre>
<p>for example</p>
<pre><code class="elixir">config :poa_backend,
:receivers,
[
{:my_receiver, POABackend.Receivers.MyReceiver, [host: &quot;localhost&quot;, port: 1234]}
]</code></pre>
<p><code class="inline">name</code>, <code class="inline">module</code> and <code class="inline">args</code> must be defined in the configuration file.</p>
<ul>
<li><code class="inline">name</code>: Name for the new created process. Must be unique
</li>
<li><code class="inline">module</code>: Module which implements the Receiver behaviour
</li>
<li><code class="inline">args</code>: Initial args which will be passed to the <code class="inline">init_receiver/1</code> function
</li>
</ul>
<p>The Receiver’s mechanism is built on top of <a href="https://hexdocs.pm/gen_stage/GenStage.html">GenStage</a>. Receivers are Consumers (sinks) and they must
be subscribed to one or more Producers. The Producers are the Metric types (i.e. <code class="inline">ethereum_metrics</code>) and are defined in the config file too:</p>
<pre><code class="elixir">config :poa_backend,
:metrics,
[
:ethereum_metrics
]</code></pre>
<p>In order to work properly we have to define in the configuration file the relation between the Receiver
and the Metric types it wants to receive. </p>
<pre><code class="elixir">config :poa_backend,
:subscriptions,
[
{receiver_name, [metric_type1, metric_type2]}
]</code></pre>
<p>for example</p>
<pre><code class="elixir">config :poa_backend,
:subscriptions,
[
{:my_receiver, [:ethereum_metrics]}
]</code></pre>
<h2 id="module-implementing-a-receiver-plugin" class="section-heading">
<a href="#module-implementing-a-receiver-plugin" class="hover-link"><span class="icon-link" aria-hidden="true"></span></a>
Implementing A Receiver Plugin
</h2>
<p>In order to implement your Receiver Plugin you must implement 3 functions.</p>
<ul>
<li><code class="inline">init_receiver/1</code>: Called only once when the process starts
</li>
<li><code class="inline">metrics_received/3</code>: This function is called eveytime the Producer (metric type) receives a message.
</li>
<li><code class="inline">handle_message/1</code>: This is called when the Receiver process receives an Erlang message
</li>
<li><code class="inline">handle_inactive/2</code>: This function is called when one client has been disconnected or is not active for a period of time.
</li>
<li><code class="inline">terminate/1</code>: Called just before stopping the process
</li>
</ul>
<p>This is a simple example of custom Receiver Plugin</p>
<pre><code class="elixir">defmodule POABackend.Receivers.MyReceiver do
use POABackend.Receiver
def init_receiver(_args) do
{:ok, :no_state}
end
def metrics_received(metrics, from, state) do
for metric &lt;- metrics do
IO.puts &quot;metric received&quot;
end
{:ok, state}
end
def handle_message(_message, state) do
{:ok, state}
end
def handle_inactive(agent_id, state) do
{:ok, state}
end
def terminate(_state) do
:ok
end
end</code></pre>
</section>
<section id="summary" class="details-list">
<h1 class="section-heading">
<a class="hover-link" href="#summary">
<span class="icon-link" aria-hidden="true"></span>
<span class="sr-only">Link to this section</span>
</a>
Summary
</h1>
<div class="summary-callbacks summary">
<h2>
<a href="#callbacks">Callbacks</a>
</h2>
<div class="summary-row">
<div class="summary-signature">
<a href="#c:handle_inactive/2">handle_inactive(agent_id, state)</a>
</div>
<div class="summary-synopsis"><p>This function is called when a Custom Handler detects a client is inactive</p>
</div>
</div>
<div class="summary-row">
<div class="summary-signature">
<a href="#c:handle_message/2">handle_message(msg, state)</a>
</div>
<div class="summary-synopsis"><p>In this callback is called when the Receiver process receives an erlang message</p>
</div>
</div>
<div class="summary-row">
<div class="summary-signature">
<a href="#c:init_receiver/1">init_receiver(args)</a>
</div>
<div class="summary-synopsis"><p>A callback executed when the Receiver Plugin starts.
The argument is retrieved from the configuration file when the Receiver is defined
It must return <code class="inline">{:ok, state}</code>, that <code class="inline">state</code> will be keept as in <a href="https://hexdocs.pm/elixir/GenServer.html"><code class="inline">GenServer</code></a> and can be
retrieved in the <code class="inline">metrics_received/3</code> function</p>
</div>
</div>
<div class="summary-row">
<div class="summary-signature">
<a href="#c:metrics_received/3">metrics_received(metrics, from, state)</a>
</div>
<div class="summary-synopsis"><p>This callback will be called every time a message to the subscribed metric type arrives. It must
return the tuple <code class="inline">{:ok, state}</code></p>
</div>
</div>
<div class="summary-row">
<div class="summary-signature">
<a href="#c:terminate/1">terminate(state)</a>
</div>
<div class="summary-synopsis"><p>This callback is called just before the Process goes down. This is a good place for closing connections</p>
</div>
</div>
</div>
</section>
<section id="callbacks" class="details-list">
<h1 class="section-heading">
<a class="hover-link" href="#callbacks">
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Callbacks
</h1>
<div class="detail" id="c:handle_inactive/2">
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<span class="signature">handle_inactive(agent_id, state)</span>
<a href="https://github.com/poanetwork/poa-netstats-wharehouse/blob/v0.1.0/lib/poa_backend/receiver.ex#L129" class="view-source" rel="help" title="View Source">
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<div class="specs">
<pre>handle_inactive(agent_id :: <a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">binary</a>(), state :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">any</a>()) :: {:ok, state :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">any</a>()}</pre>
</div>
</div>
<section class="docstring">
<p> This function is called when a Custom Handler detects a client is inactive.</p>
<p> The Custom Handler must to call explicity to <a href="POABackend.CustomHandler.html#publish_inactive/1"><code class="inline">POABackend.CustomHandler.publish_inactive/1</code></a> and it will publish the
<code class="inline">inactive</code> message to all the metrics in the system (defined in the config file).</p>
</section>
</div>
<div class="detail" id="c:handle_message/2">
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<span class="signature">handle_message(msg, state)</span>
<a href="https://github.com/poanetwork/poa-netstats-wharehouse/blob/v0.1.0/lib/poa_backend/receiver.ex#L120" class="view-source" rel="help" title="View Source">
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<div class="specs">
<pre>handle_message(msg :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">any</a>(), state :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">any</a>()) :: {:ok, state :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">any</a>()}</pre>
</div>
</div>
<section class="docstring">
<p> In this callback is called when the Receiver process receives an erlang message.</p>
<p> It must return <code class="inline">{:ok, state}</code>.</p>
</section>
</div>
<div class="detail" id="c:init_receiver/1">
<div class="detail-header">
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<span class="signature">init_receiver(args)</span>
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<div class="specs">
<pre>init_receiver(args :: <a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">term</a>()) :: {:ok, state :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">any</a>()}</pre>
</div>
</div>
<section class="docstring">
<p> A callback executed when the Receiver Plugin starts.
The argument is retrieved from the configuration file when the Receiver is defined
It must return <code class="inline">{:ok, state}</code>, that <code class="inline">state</code> will be keept as in <a href="https://hexdocs.pm/elixir/GenServer.html"><code class="inline">GenServer</code></a> and can be
retrieved in the <code class="inline">metrics_received/3</code> function.</p>
</section>
</div>
<div class="detail" id="c:metrics_received/3">
<div class="detail-header">
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<span class="signature">metrics_received(metrics, from, state)</span>
<a href="https://github.com/poanetwork/poa-netstats-wharehouse/blob/v0.1.0/lib/poa_backend/receiver.ex#L113" class="view-source" rel="help" title="View Source">
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<div class="specs">
<pre>metrics_received(metrics :: [<a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">term</a>()], from :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">pid</a>(), state :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">any</a>()) ::
{:ok, state :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">any</a>()}</pre>
</div>
</div>
<section class="docstring">
<p> This callback will be called every time a message to the subscribed metric type arrives. It must
return the tuple <code class="inline">{:ok, state}</code></p>
</section>
</div>
<div class="detail" id="c:terminate/1">
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<span class="signature">terminate(state)</span>
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<div class="specs">
<pre>terminate(state :: <a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">term</a>()) :: <a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">term</a>()</pre>
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<section class="docstring">
<p> This callback is called just before the Process goes down. This is a good place for closing connections.</p>
</section>
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