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23 <manualpage metafile="socache.xml.meta">
25 <title>Shared Object Cache in Apache HTTP Server</title>
28 <p>The Shared Object Cache provides a means to share simple data
29 across all a server's workers, regardless of <a href="mpm.html">thread
30 and process models</a>. It is used where the advantages of sharing
31 data across processes outweigh the performance overhead of
32 inter-process communication.</p>
35 <section id="providers">
36 <title>Shared Object Cache Providers</title>
37 <p>The shared object cache as such is an abstraction. Four different
38 modules implement it. To use the cache, one or more of these modules
39 must be present, and configured.</p>
40 <p>The only configuration required is to select which cache provider
41 to use. This is the responsibility of modules using the cache, and
42 they enable selecton using directives such as
43 <directive module="authn_socache">AuthnCacheSOCache</directive>,
44 <directive module="ssl">SSLSessionCache</directive>, and
45 <directive module="ssl">SSLStaplingCache</directive>.</p>
46 <p>Currently available providers are:</p>
48 <dt>"dbm" (mod_socache_dbm)</dt>
49 <dd>This makes use of a DBM hash file.
50 The choice of underlying DBM configuration may be configurable
51 if the installed APR version supports multiple DBM implementations.</dd>
52 <dt>"dc" (mod_socache_dc)</dt>
53 <dd>This makes use of the <a href="http://www.distcache.org/">distcache</a>
54 distributed session caching libraries.</dd>
55 <dt>"mc" (mod_socache_memcache)</dt>
56 <dd>This makes use of the <a href="http://memcached.org/">memcached</a>
57 high-performance, distributed memory object caching system.</dd>
58 <dt>"shmcb" (mod_socache_shmcb)</dt>
59 <dd>This makes use of a high-performance cyclic buffer inside a
60 shared memory segment.</dd>