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<title>mod_heartbeat - Apache HTTP Server Version 2.4</title>
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<div id="preamble"><h1>Apache Module mod_heartbeat</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/mod/mod_heartbeat.html" title="English"> en </a> |
<a href="../fr/mod/mod_heartbeat.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Sends messages with server status to frontend proxy</td></tr>
<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Experimental</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>heartbeat_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_heartbeat</td></tr>
<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.3 and later</td></tr></table>
<h3>Summary</h3>
<p> <code class="module"><a href="../mod/mod_heartbeat.html">mod_heartbeat</a></code> sends multicast messages to a <code class="module"><a href="../mod/mod_heartmonitor.html">mod_heartmonitor</a></code> listener
that advertises the servers current connection count. Usually, <code class="module"><a href="../mod/mod_heartmonitor.html">mod_heartmonitor</a></code>
will be running on a proxy server with <code class="module"><a href="../mod/mod_lbmethod_heartbeat.html">mod_lbmethod_heartbeat</a></code> loaded, which allows
<code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code> to use the "heartbeat" <em>lbmethod</em> inside
of <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code>.</p>
<p>
<code class="module"><a href="../mod/mod_heartbeat.html">mod_heartbeat</a></code> itself is loaded on the origin server(s) that serve requests
through the proxy server(s).
</p>
<div class="warning">
To use <code class="module"><a href="../mod/mod_heartbeat.html">mod_heartbeat</a></code>,
<code class="module"><a href="../mod/mod_status.html">mod_status</a></code> and <code class="module"><a href="../mod/mod_watchdog.html">mod_watchdog</a></code>
must be either a static modules or, if a dynamic module, must
be loaded before <code class="module"><a href="../mod/mod_heartbeat.html">mod_heartbeat</a></code>.
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<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3>Topics</h3>
<ul id="topics">
<li><img alt="" src="../images/down.gif" /> <a href="#consuming">Consuming mod_heartbeat Output</a></li>
</ul><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/down.gif" /> <a href="#heartbeataddress">HeartbeatAddress</a></li>
</ul>
<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_heartbeat">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_heartbeat">Report a bug</a></li></ul><h3>See also</h3>
<ul class="seealso">
<li><a href="#comments_section">Comments</a></li></ul></div>
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<div class="section">
<h2><a name="consuming" id="consuming">Consuming mod_heartbeat Output</a></h2>
<p>
Every 1 second, this module generates a single multicast UDP
packet, containing the number of busy and idle workers. The
packet is a simple ASCII format, similar to GET query parameters
in HTTP.
</p>
<div class="example"><h3>An Example Packet</h3><p><code>
v=1&ready=75&busy=0
</code></p></div>
<p>
Consumers should handle new variables besides busy and ready,
separated by '&', being added in the future.
</p>
</div>
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<div class="directive-section"><h2><a name="HeartbeatAddress" id="HeartbeatAddress">HeartbeatAddress</a> <a name="heartbeataddress" id="heartbeataddress">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Multicast address for heartbeat packets</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>HeartbeatAddress <var>addr:port</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>disabled</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Experimental</td></tr>
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_heartbeat</td></tr>
</table>
<p>The <code class="directive">HeartbeatAddress</code> directive specifies the
multicast address to which <code class="module"><a href="../mod/mod_heartbeat.html">mod_heartbeat</a></code> will send
status information. This address will usually correspond to a configured
<code class="directive"><a href="../mod/mod_heartmonitor.html#heartbeatlisten">HeartbeatListen</a></code> on a
frontend proxy system.</p>
<pre class="prettyprint lang-config">HeartbeatAddress 239.0.0.1:27999</pre>
</div>
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