1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- 4 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 5 This file is generated from xml source: DO NOT EDIT 6 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 7 --> 8<title>Shared Object Cache in Apache HTTP Server - Apache HTTP Server</title> 9<link href="/style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> 10<link href="/style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> 11<link href="/style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="/style/css/prettify.css" /> 12<script src="/style/scripts/prettify.min.js" type="text/javascript"> 13</script> 14 15<link href="/images/favicon.ico" rel="shortcut icon" /></head> 16<body id="manual-page" class="no-sidebar"><div id="page-header"> 17<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p> 18<p class="apache">Apache HTTP Server Version 2.4</p> 19<img alt="" src="/images/feather.gif" /></div> 20<div class="up"><a href="./"><img title="<-" alt="<-" src="/images/left.gif" /></a></div> 21<div id="path"> 22<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="./">Version 2.4</a></div><div id="page-content"><div id="preamble"><h1>Shared Object Cache in Apache HTTP Server</h1> 23<div class="toplang"> 24<p><span>Available Languages: </span><a href="/en/socache.html" title="English"> en </a> | 25<a href="/fr/socache.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a></p> 26</div> 27 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> 33 </div> 34<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 35<div class="section"> 36<h2><a name="providers" id="providers">Shared Object Cache Providers</a></h2> 37 38 <p>The shared object cache as such is an abstraction. Four different 39 modules implement it. To use the cache, one or more of these modules 40 must be present, and configured.</p> 41 <p>The only configuration required is to select which cache provider 42 to use. This is the responsibility of modules using the cache, and 43 they enable selection using directives such as 44 <code class="directive"><a href="/mod/mod_cache_socache.html#cachesocache">CacheSocache</a></code>, 45 <code class="directive"><a href="/mod/mod_authn_socache.html#authncachesocache">AuthnCacheSOCache</a></code>, 46 <code class="directive"><a href="/mod/mod_ssl.html#sslsessioncache">SSLSessionCache</a></code>, and 47 <code class="directive"><a href="/mod/mod_ssl.html#sslstaplingcache">SSLStaplingCache</a></code>.</p> 48 <p>Currently available providers are:</p> 49 <dl> 50 <dt>"dbm" (<code class="module"><a href="/mod/mod_socache_dbm.html">mod_socache_dbm</a></code>)</dt> 51 <dd>This makes use of a DBM hash file. 52 The choice of underlying DBM used may be configurable 53 if the installed APR version supports multiple DBM implementations.</dd> 54 <dt>"dc" (<code class="module"><a href="/mod/mod_socache_dc.html">mod_socache_dc</a></code>)</dt> 55 <dd>This makes use of the <a href="http://www.distcache.org/">distcache</a> 56 distributed session caching libraries.</dd> 57 <dt>"memcache" (<code class="module"><a href="/mod/mod_socache_memcache.html">mod_socache_memcache</a></code>)</dt> 58 <dd>This makes use of the <a href="http://memcached.org/">memcached</a> 59 high-performance, distributed memory object caching system.</dd> 60 <dt>"shmcb" (<code class="module"><a href="/mod/mod_socache_shmcb.html">mod_socache_shmcb</a></code>)</dt> 61 <dd>This makes use of a high-performance cyclic buffer inside a 62 shared memory segment.</dd> 63 </dl> 64 65 <p>The API provides the following functions:</p> 66 67 <dl> 68 <dt>const char *create(ap_socache_instance_t **instance, const char *arg, 69 apr_pool_t *tmp, apr_pool_t *p);</dt> 70 <dd>Create a session cache based on the given configuration string. 71 The instance pointer returned in the instance paramater will be 72 passed as the first argument to subsequent invocations.</dd> 73 74 <dt>apr_status_t init(ap_socache_instance_t *instance, const char *cname, 75 const struct ap_socache_hints *hints, 76 server_rec *s, apr_pool_t *pool)</dt> 77 <dd>Initialize the cache. The cname must be of maximum length 16 78 characters, and uniquely identifies the consumer of the cache 79 within the server; using the module name is recommended, e.g. 80 "mod_ssl-sess". This string may be used within a filesystem 81 path so use of only alphanumeric [a-z0-9_-] characters is 82 recommended. If hints is non-NULL, it gives a set of hints for 83 the provider. Return APR error code.</dd> 84 85 <dt>void destroy(ap_socache_instance_t *instance, server_rec *s)</dt> 86 <dd>Destroy a given cache instance object.</dd> 87 88 <dt>apr_status_t store(ap_socache_instance_t *instance, server_rec *s, 89 const unsigned char *id, unsigned int idlen, 90 apr_time_t expiry, 91 unsigned char *data, unsigned int datalen, 92 apr_pool_t *pool)</dt> 93 <dd>Store an object in a cache instance.</dd> 94 95 <dt>apr_status_t retrieve(ap_socache_instance_t *instance, server_rec *s, 96 const unsigned char *id, unsigned int idlen, 97 unsigned char *data, unsigned int *datalen, 98 apr_pool_t *pool)</dt> 99 <dd>Retrieve a cached object.</dd> 100 101 <dt>apr_status_t remove(ap_socache_instance_t *instance, server_rec *s, 102 const unsigned char *id, unsigned int idlen, 103 apr_pool_t *pool)</dt> 104 <dd>Remove an object from the cache.</dd> 105 106 <dt>void status(ap_socache_instance_t *instance, request_rec *r, int flags)</dt> 107 <dd>Dump the status of a cache instance for mod_status.</dd> 108 109 <dt>apr_status_t iterate(ap_socache_instance_t *instance, server_rec *s, 110 void *userctx, ap_socache_iterator_t *iterator, 111 apr_pool_t *pool)</dt> 112 <dd>Dump all cached objects through an iterator callback.</dd> 113 </dl> 114 115 </div></div> 116<div class="bottomlang"> 117<p><span>Available Languages: </span><a href="/en/socache.html" title="English"> en </a> | 118<a href="/fr/socache.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a></p> 119</div><div class="top"><a href="#page-header"><img src="/images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. 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