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&lt;title&gt;mod_heartbeat - Apache HTTP Server Version 2.4&lt;/title&gt;
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&lt;div id=&quot;preamble&quot;&gt;&lt;h1&gt;Apache Module mod_heartbeat&lt;/h1&gt;
&lt;div class=&quot;toplang&quot;&gt;
&lt;p&gt;&lt;span&gt;Available Languages: &lt;/span&gt;&lt;a href=&quot;../en/mod/mod_heartbeat.html&quot; title=&quot;English&quot;&gt;&amp;nbsp;en&amp;nbsp;&lt;/a&gt; |
&lt;a href=&quot;../fr/mod/mod_heartbeat.html&quot; hreflang=&quot;fr&quot; rel=&quot;alternate&quot; title=&quot;Français&quot;&gt;&amp;nbsp;fr&amp;nbsp;&lt;/a&gt;&lt;/p&gt;
&lt;/div&gt;
&lt;table class=&quot;module&quot;&gt;&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;module-dict.html#Description&quot;&gt;Description:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;Sends messages with server status to frontend proxy&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;module-dict.html#Status&quot;&gt;Status:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;Experimental&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;module-dict.html#ModuleIdentifier&quot;&gt;Module Identifier:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;heartbeat_module&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;module-dict.html#SourceFile&quot;&gt;Source File:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;mod_heartbeat&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;module-dict.html#Compatibility&quot;&gt;Compatibility:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;Available in Apache 2.3 and later&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;
&lt;h3&gt;Summary&lt;/h3&gt;

&lt;p&gt; &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_heartbeat.html&quot;&gt;mod_heartbeat&lt;/a&gt;&lt;/code&gt; sends multicast messages to a &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_heartmonitor.html&quot;&gt;mod_heartmonitor&lt;/a&gt;&lt;/code&gt; listener 
that advertises the servers current connection count.  Usually, &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_heartmonitor.html&quot;&gt;mod_heartmonitor&lt;/a&gt;&lt;/code&gt;
will be running on a proxy server with &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_lbmethod_heartbeat.html&quot;&gt;mod_lbmethod_heartbeat&lt;/a&gt;&lt;/code&gt; loaded, which allows
&lt;code class=&quot;directive&quot;&gt;&lt;a href=&quot;../mod/mod_proxy.html#proxypass&quot;&gt;ProxyPass&lt;/a&gt;&lt;/code&gt; to use the &quot;heartbeat&quot; &lt;em&gt;lbmethod&lt;/em&gt; inside
of &lt;code class=&quot;directive&quot;&gt;&lt;a href=&quot;../mod/mod_proxy.html#proxypass&quot;&gt;ProxyPass&lt;/a&gt;&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;
    &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_heartbeat.html&quot;&gt;mod_heartbeat&lt;/a&gt;&lt;/code&gt; itself is loaded on the origin server(s) that serve requests 
    through the proxy server(s).  
&lt;/p&gt;

    &lt;div class=&quot;warning&quot;&gt;
        To use &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_heartbeat.html&quot;&gt;mod_heartbeat&lt;/a&gt;&lt;/code&gt;,
        &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_status.html&quot;&gt;mod_status&lt;/a&gt;&lt;/code&gt; and &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_watchdog.html&quot;&gt;mod_watchdog&lt;/a&gt;&lt;/code&gt;
        must be either a static modules or, if a dynamic module, must
        be loaded before &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_heartbeat.html&quot;&gt;mod_heartbeat&lt;/a&gt;&lt;/code&gt;.
    &lt;/div&gt;

&lt;/div&gt;
&lt;div id=&quot;quickview&quot;&gt;&lt;a href=&quot;https://www.apache.org/foundation/contributing.html&quot; class=&quot;badge&quot;&gt;&lt;img src=&quot;https://www.apache.org/images/SupportApache-small.png&quot; alt=&quot;Support Apache!&quot; /&gt;&lt;/a&gt;&lt;h3&gt;Topics&lt;/h3&gt;
&lt;ul id=&quot;topics&quot;&gt;
&lt;li&gt;&lt;img alt=&quot;&quot; src=&quot;../images/down.gif&quot; /&gt; &lt;a href=&quot;#consuming&quot;&gt;Consuming mod_heartbeat Output&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;&lt;h3 class=&quot;directives&quot;&gt;Directives&lt;/h3&gt;
&lt;ul id=&quot;toc&quot;&gt;
&lt;li&gt;&lt;img alt=&quot;&quot; src=&quot;../images/down.gif&quot; /&gt; &lt;a href=&quot;#heartbeataddress&quot;&gt;HeartbeatAddress&lt;/a&gt;&lt;/li&gt;
&lt;/ul&gt;
&lt;h3&gt;Bugfix checklist&lt;/h3&gt;&lt;ul class=&quot;seealso&quot;&gt;&lt;li&gt;&lt;a href=&quot;https://www.apache.org/dist/httpd/CHANGES_2.4&quot;&gt;httpd changelog&lt;/a&gt;&lt;/li&gt;&lt;li&gt;&lt;a href=&quot;https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&amp;amp;list_id=144532&amp;amp;product=Apache%20httpd-2&amp;amp;query_format=specific&amp;amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;amp;component=mod_heartbeat&quot;&gt;Known issues&lt;/a&gt;&lt;/li&gt;&lt;li&gt;&lt;a href=&quot;https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;amp;component=mod_heartbeat&quot;&gt;Report a bug&lt;/a&gt;&lt;/li&gt;&lt;/ul&gt;&lt;h3&gt;See also&lt;/h3&gt;
&lt;ul class=&quot;seealso&quot;&gt;
&lt;li&gt;&lt;a href=&quot;#comments_section&quot;&gt;Comments&lt;/a&gt;&lt;/li&gt;&lt;/ul&gt;&lt;/div&gt;
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&lt;div class=&quot;section&quot;&gt;
&lt;h2&gt;&lt;a name=&quot;consuming&quot; id=&quot;consuming&quot;&gt;Consuming mod_heartbeat Output&lt;/a&gt;&lt;/h2&gt;
    
  &lt;p&gt;
      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.
  &lt;/p&gt;
  
&lt;div class=&quot;example&quot;&gt;&lt;h3&gt;An Example Packet&lt;/h3&gt;&lt;p&gt;&lt;code&gt;
v=1&amp;amp;ready=75&amp;amp;busy=0
&lt;/code&gt;&lt;/p&gt;&lt;/div&gt;

  &lt;p&gt;
    Consumers should handle new variables besides busy and ready,
    separated by &#039;&amp;amp;&#039;, being added in the future.
  &lt;/p&gt;

&lt;/div&gt;
&lt;div class=&quot;top&quot;&gt;&lt;a href=&quot;#page-header&quot;&gt;&lt;img alt=&quot;top&quot; src=&quot;../images/up.gif&quot; /&gt;&lt;/a&gt;&lt;/div&gt;
&lt;div class=&quot;directive-section&quot;&gt;&lt;h2&gt;&lt;a name=&quot;HeartbeatAddress&quot; id=&quot;HeartbeatAddress&quot;&gt;HeartbeatAddress&lt;/a&gt; &lt;a name=&quot;heartbeataddress&quot; id=&quot;heartbeataddress&quot;&gt;Directive&lt;/a&gt;&lt;/h2&gt;
&lt;table class=&quot;directive&quot;&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;directive-dict.html#Description&quot;&gt;Description:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;Multicast address for heartbeat packets&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;directive-dict.html#Syntax&quot;&gt;Syntax:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;&lt;code&gt;HeartbeatAddress &lt;var&gt;addr:port&lt;/var&gt;&lt;/code&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;directive-dict.html#Default&quot;&gt;Default:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;&lt;code&gt;disabled&lt;/code&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;directive-dict.html#Context&quot;&gt;Context:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;server config&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;directive-dict.html#Status&quot;&gt;Status:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;Experimental&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;th&gt;&lt;a href=&quot;directive-dict.html#Module&quot;&gt;Module:&lt;/a&gt;&lt;/th&gt;&lt;td&gt;mod_heartbeat&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;
&lt;p&gt;The &lt;code class=&quot;directive&quot;&gt;HeartbeatAddress&lt;/code&gt; directive specifies the
multicast address to which &lt;code class=&quot;module&quot;&gt;&lt;a href=&quot;../mod/mod_heartbeat.html&quot;&gt;mod_heartbeat&lt;/a&gt;&lt;/code&gt; will send
status information. This address will usually correspond to a configured
 &lt;code class=&quot;directive&quot;&gt;&lt;a href=&quot;../mod/mod_heartmonitor.html#heartbeatlisten&quot;&gt;HeartbeatListen&lt;/a&gt;&lt;/code&gt; on a
frontend proxy system.&lt;/p&gt;
&lt;pre class=&quot;prettyprint lang-config&quot;&gt;HeartbeatAddress 239.0.0.1:27999&lt;/pre&gt;
    

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