Document socache and fix the TODO in authn_socache docs.

<override>None</override>

<usage>

    <p>This is a server-wide setting.  If not set, your platform's

    <p>This is a server-wide setting to select a provider for the

    <a href="../socache.html">shared object cache</a>.

    Values are "dbm", "dc", "mc", or "shmcb", each subject to the

    appropriate module being loaded.  If not set, your platform's

       default will be used.</p>

    <note><title>socache</title>

      <p>The cache is built on the the <var>socache</var> framework.

      We need a link here once that's documented!</p>

    </note>

</usage>

</directivesynopsis>

<page href="bind.html">Setting which addresses and ports Apache uses</page>

<page href="mpm.html">Multi-Processing Modules (MPMs)</page>

<page href="env.html">Environment Variables in Apache</page>

<page href="expr.html">Expression Parsing in Apache</page>

<page href="handler.html">Apache's Handler Use</page>

<page href="filter.html">Filters</page>

<page href="socache.html">Shared Object Cache Support</page>

<page href="suexec.html">suEXEC Support</page>

<page href="misc/perf-tuning.html">Performance Hints</page>

<page href="http://wiki.apache.org/httpd/FAQ">Frequently Asked Questions</page>

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

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

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

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<manualpage metafile="socache.xml.meta">

  <title>Shared Object Cache in Apache HTTP Server</title>

  <summary>

    <p>The Shared Object Cache provides a means to share simple data

    across all a server's workers, regardless of <a href="mpm.html">thread

    and process models</a>.  It is used where the advantages of sharing

    data across processes outweigh the performance overhead of

    inter-process communication.</p>

  </summary>

<seealso><module>mod_socache_dbm</module></seealso>

<seealso><module>mod_socache_dc</module></seealso>

<seealso><module>mod_socache_memcache</module></seealso>

<seealso><module>mod_socache_shmcb</module></seealso>

  <section id="providers">

    <title>Shared Object Cache Providers</title>

    <p>The shared object cache as such is an abstraction.  Four different

    modules implement it.  To use the cache, one or more of these modules

    must be present, and configured.</p>

    <p>The only configuration required is to select which cache provider

    to use.  This is the responsibility of modules using the cache, and

    they enable selecton using directives such as

    <directive module="authn_socache">AuthnCacheSOCache</directive>,

    <directive module="ssl">SSLSessionCache</directive>, and

    <directive module="ssl">SSLStaplingCache</directive>.</p>

    <p>Currently available providers are:</p>

    <dl>

    <dt><module>mod_socache_dbm</module> ("dbm")</dt>

    <dd>This makes use of a DBM hash file.

     The choice of underlying DBM configuration may be configurable

     if the installed APR version supports multiple DBM implementations.</dd>

    <dt><module>mod_socache_dc</module> ("dc")</dt>

    <dd>This makes use of the <a href="http://www.distcache.org/">distcache</a>

    distributed session caching libraries.</dd>

    <dt><module>mod_socache_memcache</module> ("mc")</dt>

    <dd>This makes use of the <a href="http://memcached.org/">memcached</a>

    high-performance, distributed memory object caching system.</dd>

    <dt><module>mod_socache_shmcb</module> ("shmcb")</dt>

    <dd>This makes use of a high-performance cyclic buffer inside a

     shared memory segment.</dd>

    </dl>

  </section>

</manualpage>

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

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

<metafile reference="socache.xml">

  <basename>socache</basename>

  <path>/</path>

  <relpath>.</relpath>

  <variants>

    <variant>en</variant>

  </variants>

</metafile>