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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
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This file is generated from xml source: DO NOT EDIT
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<title>mod_authn_socache - Apache HTTP Server</title>
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<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
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<body>
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<div id="page-header">
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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
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<p class="apache">Apache HTTP Server Version 2.5</p>
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<img alt="" src="../images/feather.gif" /></div>
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<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
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<div id="path">
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<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 2.5</a> > <a href="./">Modules</a></div>
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<div id="page-content">
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<div id="preamble"><h1>Apache Module mod_authn_socache</h1>
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<div class="toplang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_authn_socache.html" title="English"> en </a></p>
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</div>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Manages a cache of authentication credentials to relieve
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the load on backends</td></tr>
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<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Base</td></tr>
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<tr><th><a href="module-dict.html#ModuleIdentifier">Module<EFBFBD>Identifier:</a></th><td>authn_socache_module</td></tr>
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<tr><th><a href="module-dict.html#SourceFile">Source<EFBFBD>File:</a></th><td>mod_authn_socache.c</td></tr>
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<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Version 2.3 and later</td></tr></table>
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<h3>Summary</h3>
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<p>Maintains a cache of authentication credentials, so that a new backend
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lookup is not required for every authenticated request.</p>
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</div>
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<div id="quickview"><h3 class="directives">Directives</h3>
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<ul id="toc">
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<li><img alt="" src="../images/down.gif" /> <a href="#authncachecontext">AuthnCacheContext</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#authncacheenable">AuthnCacheEnable</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#authncacheprovidefor">AuthnCacheProvideFor</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#authncachesocache">AuthnCacheSOCache</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#authncachetimeout">AuthnCacheTimeout</a></li>
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</ul>
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<h3>Topics</h3>
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<ul id="topics">
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<li><img alt="" src="../images/down.gif" /> <a href="#intro">Authentication Cacheing</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#usage">Usage</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#dev">Cacheing with custom modules</a></li>
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</ul></div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="intro" id="intro">Authentication Cacheing</a></h2>
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<p>Some users of more heavyweight authentication such as SQL database
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lookups (<code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code>) have reported it putting an
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unacceptable load on their authentication provider. A typical case
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in point is where an HTML page contains hundreds of objects
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(images, scripts, stylesheets, media, etc), and a request to the page
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generates hundreds of effectively-immediate requests for authenticated
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additional contents.</p>
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<p>mod_authn_socache provides a solution to this problem by
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maintaining a cache of authentication credentials.</p>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="usage" id="usage">Usage</a></h2>
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<p>The authentication cache should be used where authentication
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lookups impose a significant load on the server, or a backend or
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network. Authentication by file (<code class="module"><a href="../mod/mod_authn_file.html">mod_authn_file</a></code>)
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or dbm (<code class="module"><a href="../mod/mod_authn_dbm.html">mod_authn_dbm</a></code>) are unlikely to benefit,
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as these are fast and lightweight in their own right (though in some
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cases, such as a network-mounted file, cacheing may be worthwhile).
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Other providers such as SQL or LDAP based authentication are more
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likely to benefit, particularly where there is an observed
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performance issue. Amongst the standard modules, <code class="module"><a href="../mod/mod_authnz_ldap.html">mod_authnz_ldap</a></code> manages its own cache, so only
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<code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code> will usually benefit from this cache.</p>
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<p>The basic rules to cache for a provider are:</p>
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<ol><li>Include the provider you're cacheing for in an
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<code class="directive">AuthnCacheProvideFor</code> directive.</li>
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<li>List <var>socache</var> ahead of the provider you're
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cacheing for in your <code class="directive"><a href="../mod/mod_auth_basic.html#authbasicprovider">AuthBasicProvider</a></code> or <code class="directive"><a href="../mod/mod_auth_digest.html#authdigestprovider">AuthDigestProvider</a></code> directive.</li>
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</ol>
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<p>A simple usage example to accelerate <code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code>
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using dbm as a cache engine:</p>
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<pre class="prettyprint lang-config">
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<Directory /usr/www/myhost/private>
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AuthType Basic
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AuthName "Cached Authentication Example"
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AuthBasicProvider socache dbd
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AuthDBDUserPWQuery "SELECT password FROM authn WHERE user = %s"
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AuthnCacheProvideFor dbd
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AuthnCacheContext dbd-authn-example
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AuthnCacheSOCache dbm
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Require valid-user
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</Directory>
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</pre>
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</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="dev" id="dev">Cacheing with custom modules</a></h2>
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<p>Module developers should note that their modules must be enabled
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for cacheing with mod_authn_socache. A single optional API function
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<var>ap_authn_cache_store</var> is provided to cache credentials
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a provider has just looked up or generated. Usage examples are
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available in <a href="http://svn.eu.apache.org/viewvc?view=revision&revision=957072">r957072</a>, in which three authn providers are enabled for cacheing.</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="AuthnCacheContext" id="AuthnCacheContext">AuthnCacheContext</a> <a name="authncachecontext" id="authncachecontext">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify a context string for use in the cache key</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheContext <var>directory|server|custom-string</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>directory</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
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</table>
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<p>This directive specifies a string to be used along with the supplied
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username (and realm in the case of Digest Authentication) in constructing
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a cache key. This serves to disambiguate identical usernames serving
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different authentication areas on the server.</p>
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<p>Two special values for this are <var>directory</var>, which uses
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the directory context of the request as a string, and <var>server</var>
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which uses the virtual host name.</p>
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<p>The default is <var>directory</var>, which is also the most
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conservative setting. This is likely to be less than optimal, as it
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(for example) causes <var>$app-base</var>, <var>$app-base/images</var>,
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<var>$app-base/scripts</var> and <var>$app-base/media</var> each to
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have its own separate cache key. A better policy is to name the
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<code class="directive">AuthnCacheContext</code> for the password
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provider: for example a <var>htpasswd</var> file or database table.</p>
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<p>Contexts can be shared across different areas of a server, where
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credentials are shared. However, this has potential to become a vector
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for cross-site or cross-application security breaches, so this directive
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is not permitted in <var>.htaccess</var> contexts.</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="AuthnCacheEnable" id="AuthnCacheEnable">AuthnCacheEnable</a> <a name="authncacheenable" id="authncacheenable">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable Authn caching configured anywhere</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheEnable</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
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<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>None</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
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</table>
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<p>This directive is not normally necessary: it is implied if
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authentication cacheing is enabled anywhere in <var>httpd.conf</var>.
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However, if it is not enabled anywhere in <var>httpd.conf</var>
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it will by default not be initialised, and is therefore not
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available in a <var>.htaccess</var> context. This directive
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ensures it is initialised so it can be used in <var>.htaccess</var>.</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="AuthnCacheProvideFor" id="AuthnCacheProvideFor">AuthnCacheProvideFor</a> <a name="authncacheprovidefor" id="authncacheprovidefor">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Specify which authn provider(s) to cache for</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheProvideFor <var>authn-provider</var> [...]</code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>None</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
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<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>AuthConfig</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
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</table>
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<p>This directive specifies an authentication provider or providers
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to cache for. Credentials found by a provider not listed in an
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AuthnCacheProvideFor directive will not be cached.</p>
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<p>For example, to cache credentials found by <code class="module"><a href="../mod/mod_authn_dbd.html">mod_authn_dbd</a></code>
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or by a custom provider <var>myprovider</var>, but leave those looked
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up by lightweight providers like file or dbm lookup alone:</p>
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<pre class="prettyprint lang-config">
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AuthnCacheProvideFor dbd myprovider
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</pre>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="AuthnCacheSOCache" id="AuthnCacheSOCache">AuthnCacheSOCache</a> <a name="authncachesocache" id="authncachesocache">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Select socache backend provider to use</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheSOCache <var>provider-name</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr>
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<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>None</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
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</table>
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<p>This is a server-wide setting to select a provider for the
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<a href="../socache.html">shared object cache</a>.
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Values are "dbm", "dc", "memcache", or "shmcb", each subject to the
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appropriate module being loaded. If not set, your platform's
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default will be used.</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="AuthnCacheTimeout" id="AuthnCacheTimeout">AuthnCacheTimeout</a> <a name="authncachetimeout" id="authncachetimeout">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Set a timeout for cache entries</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>AuthnCacheTimeout <var>timeout</var> (seconds)</code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>300 (5 minutes)</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>directory, .htaccess</td></tr>
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<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>AuthConfig</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_authn_socache</td></tr>
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</table>
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<p>Cacheing authentication data can be a security issue, though short-term
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cacheing is unlikely to be a problem. Typically a good solution is to
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cache credentials for as long as it takes to relieve the load on a
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backend, but no longer, though if changes to your users and passwords
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are infrequent then a longer timeout may suit you. The default 300
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seconds (5 minutes) is both cautious and ample to keep the load
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on a backend such as dbd (SQL database queries) down.</p>
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<p>This should not be confused with session timeout, which is an
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entirely separate issue. However, you may wish to check your
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session-management software for whether cached credentials can
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"accidentally" extend a session, and bear it in mind when setting
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your timeout.</p>
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</div>
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</div>
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<div class="bottomlang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_authn_socache.html" title="English"> en </a></p>
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</div><div id="footer">
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<p class="apache">Copyright 2012 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
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