Update heartbeat module documentation, add documentation for mod_watchdog

  Start is in expr.xml, igalic is working on this

- modules docs

    - the follwing modules added since 2.2 lack documentation

    - the following modules added since 2.2 lack documentation

        - mod_serf

        - mod_watchdog

        - mod_heartbeat

        - mod_heartmonitor

        - mod_lbmethod_heartbeat

        - mpm_simple

      the list may be incomplete

      maybe some of the modules will not be included in 2.4

will be running on a proxy server with <module>mod_lbmethod_heartbeat</module> loaded, which allows

<directive module="mod_proxy">ProxyPass</directive> to use the "heartbeat" <em>lbmethod</em> inside

of <directive module="mod_proxy">ProxyPass</directive>.</p>

<p>

    <module>mod_heartbeat</module> itself is loaded on the origin server(s) that serve requests 

    through the proxy server(s).  

</p>

    <note type="warning">

        To use <module>mod_heartbeat</module>,

        <module>mod_status</module> and <module>mod_watchdog</module>

        must be either a static modules or, if a dynamic module, it must

        be loaded before <module>mod_heartbeat</module>.

    </note>

</summary>

<section id="consuming">

    <title>Consuming mod_heartbeat Output</title>

  <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, similiar to GET query parameters

      in HTTP.

  </p>

<example><title>An Example Packet</title>

v=1&ready=75&busy=0

</example>

  <p>

    Consumers should handle new variables besides busy and ready,

    separated by '&', being added in the future.

  </p>

</section>

<section id="miscellaneous">

<title>Miscellaneous</title>

<p>The interval of 1 seconds is controlled by the HEARTBEAT_INTERVAL

compile time define.  This is not currently tunable at run time. To make

this module send the status packet more often, you must add to the

CFLAGS used to compile the module to include:</p>

<example>-DHEARTBEAT_INTERVAL=3</example>

<p>Would cause the broadcasts to be sent every 3 seconds.</p>

</section>    

<directivesynopsis>

<name>HeartbeatAddress</name>

<description>Address to send heartbeat requests</description>

<description>Multicast address for heartbeat packets</description>

<syntax>HeartbeatAddress <var>addr:port</var></syntax>

<default>disabled</default>

<contextlist><context>server config</context></contextlist>

<usage>

<p>The <directive>HeartbeatAddress</directive> directive specifies the

    address <module>mod_heartbeat</module> will send status information to. This

    address will usually corrspond to a configured  <directive

    module="mod_heartmonitor">HeartbeatListen</directive> on a frontend

    proxy system.  </p>

multicast address to which <module>mod_heartbeat</module> will send

status information. This address will usually correspond to a configured

 <directive module="mod_heartmonitor">HeartbeatListen</directive> on a

frontend proxy system.</p>

<example>

HeartbeatAddress 239.0.0.1:27999

</example>    

</usage>

</directivesynopsis>

 limitations under the License.

-->

<modulesynopsis metafile="mod_heartbeat.xml.meta">

<modulesynopsis metafile="mod_heartmonitor.xml.meta">

<name>mod_heartmonitor</name>

<description>centralized monitor for mod_heartbeat origin servers</description>

<status>Experimental</status>

<sourcefile>mod_heartmonitor</sourcefile>

<sourcefile>mod_heartmonitor.c</sourcefile>

<identifier>heartmonitor_module</identifier>

<compatibility>Available in Apache 2.3 and later</compatibility>

<summary>

<p>

<module>mod_heartmonitor</module> listens for server status messages generated 

by <module>mod_heartbeat</module> enabled servers and makes their status 

by <module>mod_heartbeat</module> enabled origin servers and makes their status 

available to <module>mod_lbmethod_heartbeat</module>. This allows 

<directive module="mod_proxy">ProxyPass</directive> to use the "heartbeat" 

<em>lbmethod</em> inside of <directive module="mod_proxy">ProxyPass</directive>.

<p>This module uses the services of <module>mod_slotmem_shm</module> when

available instead of flat-file storage.  No configuration is required to

use <module>mod_slotmem_shm</module>.</p>

    <note type="warning">

        To use <module>mod_heartmonitor</module>,

        <module>mod_status</module> and <module>mod_watchdog</module>

        must be either a static modules or, if a dynamic module, it must

        be loaded before <module>mod_heartmonitor</module>.

    </note>

</summary>

<directivesynopsis>

<name>HeartbeatListen</name>

<description>address to listen for incoming heartbeat requests </description>

<description>multicast address to listen for incoming heartbeat requests </description>

<syntax>HeartbeatListen<var>addr:port</var></syntax>

<default>disabled</default>

<contextlist><context>server config</context></contextlist>

<usage>

    <p>The <directive>HeartbeatListen</directive> directive specifies the

    address the server will listen on for status information from 

    multicast address on which the server will listen for status information from 

    <module>mod_heartbeat</module>-enabled servers.  This

    address will usually corrspond to a configured  <directive

    module="mod_heartbeat">HeartbeatAddress</directive> on an origin server.

    </p>

    <example>

    HeartbeatListen 239.0.0.1:27999

    </example>

    <p> This module is inactive until this directive is used.</p>

</usage>

</directivesynopsis>

    <p>The <directive>HeartbeatMaxServers</directive> directive specifies the

    maximum number of servers that will be sending requests to this monitor

    server.  It is used to control the size of the shared memory allocated

    to store the heartbeat info.</p>

    to store the heartbeat info when <module>mod_slotmem_shm</module> is in use.</p>

</usage>

</directivesynopsis>

</modulesynopsis>

<?xml version="1.0"?>

<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">

<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>

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<modulesynopsis metafile="mod_watchdog.xml.meta">

<name>mod_watchdog</name>

<description>provides infrastructure for other modules to periodically run 

    tasks</description>

<status>Base</status>

<sourcefile>mod_watchdog.c</sourcefile>

<identifier>watchdog_module</identifier>

<compatibility>Available in Apache 2.3 and later</compatibility>

<summary>

<p><module>mod_watchdog</module> defines programmatic hooks for other modules to 

periodically run tasks.  These modules can register handlers for 

<module>mod_watchdog</module> hooks.  Currently, the following modules in the 

Apache distribution use this functionality:</p> 

<ul>

<li><module>mod_heartbeat</module></li>

<li><module>mod_heartmonitor</module></li>

</ul>

<note type="warning">

To allow a module to use <module>mod_watchdog</module> functionality, 

<module>mod_watchdog</module> itself must be statically linked to the server 

core or, if a dynamic module, be loaded before the calling module. 

</note>

</summary>

<directivesynopsis>

<name>WatchdogInterval</name>

<description>Watchdog interval in seconds</description>

<syntax>WatchdogInterval <var>number-of-seconds</var></syntax>

<default>WatchdogInterval 1</default>

<contextlist><context>server config</context></contextlist>

<usage>

Sets the interval at which the watchdog_step hook runs.  Default is to run every 

second.

</usage>

</directivesynopsis>

</modulesynopsis>

<?xml version="1.0" encoding="UTF-8" ?>

<!-- GENERATED FROM XML: DO NOT EDIT -->

<metafile reference="mod_watchdog.xml">

  <basename>mod_watchdog</basename>

  <path>/mod/</path>

  <relpath>..</relpath>

  <variants>

    <variant>en</variant>

  </variants>

</metafile>