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661 lines
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<?xml version="1.0" encoding="ISO-8859-1"?>
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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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<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
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XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
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This file is generated from xml source: DO NOT EDIT
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XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
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-->
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<title>mod_cache - 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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<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
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<link href="../images/favicon.ico" rel="shortcut icon" /></head>
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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 2.3</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 2.3</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_cache</h1>
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<div class="toplang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_cache.html" title="English"> en </a> |
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<a href="../ja/mod/mod_cache.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
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<a href="../ko/mod/mod_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </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>Content cache keyed to URIs.</td></tr>
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<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="module-dict.html#ModuleIdentifier">Module<EFBFBD>Identifier:</a></th><td>cache_module</td></tr>
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<tr><th><a href="module-dict.html#SourceFile">Source<EFBFBD>File:</a></th><td>mod_cache.c</td></tr></table>
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<h3>Summary</h3>
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<div class="warning">This module should be used with care and
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can be used to circumvent <code class="directive"><a href="../mod/mod_authz_host.html#allow">Allow</a></code> and <code class="directive"><a href="../mod/mod_authz_host.html#deny">Deny</a></code> directives. You
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||
should not enable caching for any content to which you wish
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to limit access by client host name, address or environment
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variable.</div>
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<p><code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> implements an <a href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</a> compliant HTTP
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content cache that can be used to cache either local or proxied content.
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<code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> requires the services of one or more storage
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management modules. One storage management module is included in
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the base Apache distribution:</p>
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<dl>
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<dt><code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code></dt>
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<dd>implements a disk based storage manager.</dd>
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</dl>
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<p>Content is stored in and retrieved from the cache using URI based keys. Content with
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access protection is not cached.</p>
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<p>Further details, discussion, and examples, are provided in the
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<a href="../caching.html">Caching Guide</a>.</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="#cachedefaultexpire">CacheDefaultExpire</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cachedisable">CacheDisable</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cacheenable">CacheEnable</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cacheignorecachecontrol">CacheIgnoreCacheControl</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cacheignoreheaders">CacheIgnoreHeaders</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cacheignorenolastmod">CacheIgnoreNoLastMod</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cacheignorequerystring">CacheIgnoreQueryString</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cacheignoreurlsessionidentifiers">CacheIgnoreURLSessionIdentifiers</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cachelastmodifiedfactor">CacheLastModifiedFactor</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cachelock">CacheLock</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cachelockmaxage">CacheLockMaxAge</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cachelockpath">CacheLockPath</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#cachemaxexpire">CacheMaxExpire</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#cacheminexpire">CacheMinExpire</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#cachestorenostore">CacheStoreNoStore</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#cachestoreprivate">CacheStorePrivate</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="#related">Related Modules and Directives</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#sampleconf">Sample Configuration</a></li>
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||
<li><img alt="" src="../images/down.gif" /> <a href="#thunderingherd">Avoiding the Thundering Herd</a></li>
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||
</ul><h3>See also</h3>
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||
<ul class="seealso">
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||
<li><a href="../caching.html">Caching Guide</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="related" id="related">Related Modules and Directives</a></h2>
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<table class="related"><tr><th>Related Modules</th><th>Related Directives</th></tr><tr><td><ul><li><code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code></li></ul></td><td><ul><li><code class="directive"><a href="../mod/mod_disk_cache.html#cacheroot">CacheRoot</a></code></li><li><code class="directive"><a href="../mod/mod_disk_cache.html#cachedirlevels">CacheDirLevels</a></code></li><li><code class="directive"><a href="../mod/mod_disk_cache.html#cachedirlength">CacheDirLength</a></code></li><li><code class="directive"><a href="../mod/mod_disk_cache.html#cacheminfilesize">CacheMinFileSize</a></code></li><li><code class="directive"><a href="../mod/mod_disk_cache.html#cachemaxfilesize">CacheMaxFileSize</a></code></li></ul></td></tr></table>
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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="sampleconf" id="sampleconf">Sample Configuration</a></h2>
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<div class="example"><h3>Sample httpd.conf</h3><p><code>
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#<br />
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# Sample Cache Configuration<br />
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#<br />
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LoadModule cache_module modules/mod_cache.so<br />
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<br />
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<IfModule mod_cache.c><br />
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<span class="indent">
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LoadModule disk_cache_module modules/mod_disk_cache.so<br />
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<IfModule mod_disk_cache.c><br />
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<span class="indent">
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CacheRoot c:/cacheroot<br />
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CacheEnable disk /<br />
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CacheDirLevels 5<br />
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CacheDirLength 3<br />
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</span>
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</IfModule> <br />
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<br />
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# When acting as a proxy, don't cache the list of security updates<br />
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CacheDisable http://security.update.server/update-list/<br />
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</span>
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</IfModule>
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</code></p></div>
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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="thunderingherd" id="thunderingherd">Avoiding the Thundering Herd</a></h2>
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<p>When a cached entry becomes stale, <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> will submit
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a conditional request to the backend, which is expected to confirm whether the
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cached entry is still fresh, and send an updated entity if not.</p>
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<p>A small but finite amount of time exists between the time the cached entity
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becomes stale, and the time the stale entity is fully refreshed. On a busy
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server, a significant number of requests might arrive during this time, and
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cause a <strong>thundering herd</strong> of requests to strike the backend
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suddenly and unpredicably.</p>
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<p>To keep the thundering herd at bay, the <code class="directive">CacheLock</code>
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directive can be used to define a directory in which locks are created for
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URLs <strong>in flight</strong>. The lock is used as a <strong>hint</strong>
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by other requests to either suppress an attempt to cache (someone else has
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gone to fetch the entity), or to indicate that a stale entry is being refreshed
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(stale content will be returned in the mean time).
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</p>
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<h3>Initial caching of an entry</h3>
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<p>When an entity is cached for the first time, a lock will be created for the
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entity until the response has been fully cached. During the lifetime of the
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lock, the cache will suppress the second and subsequent attempt to cache the
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same entity. While this doesn't hold back the thundering herd, it does stop
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the cache attempting to cache the same entity multiple times simultaneously.
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</p>
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<h3>Refreshment of a stale entry</h3>
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<p>When an entity reaches its freshness lifetime and becomes stale, a lock
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will be created for the entity until the response has either been confirmed as
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still fresh, or replaced by the backend. During the lifetime of the lock, the
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second and subsequent incoming request will cause stale data to be returned,
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and the thundering herd is kept at bay.</p>
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<h3>Locks and Cache-Control: no-cache</h3>
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<p>Locks are used as a <strong>hint only</strong> to enable the cache to be
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more gentle on backend servers, however the lock can be overridden if necessary.
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If the client sends a request with a Cache-Control header forcing a reload, any
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lock that may be present will be ignored, and the client's request will be
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honoured immediately and the cached entry refreshed.</p>
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<p>As a further safety mechanism, locks have a configurable maximum age.
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Once this age has been reached, the lock is removed, and a new request is
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given the opportunity to create a new lock. This maximum age can be set using
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the <code class="directive">CacheLockMaxAge</code> directive, and defaults to 5
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seconds.
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||
</p>
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<h3>Example configuration</h3>
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||
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<div class="example"><h3>Enabling the cache lock</h3><p><code>
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||
#<br />
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||
# Enable the cache lock<br />
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||
#<br />
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<IfModule mod_cache.c><br />
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||
<span class="indent">
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||
CacheLock on<br />
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CacheLockPath /tmp/mod_cache-lock<br />
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CacheLockMaxAge 5<br />
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</span>
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||
</IfModule>
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||
</code></p></div>
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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="CacheDefaultExpire" id="CacheDefaultExpire">CacheDefaultExpire</a> <a name="cachedefaultexpire" id="cachedefaultexpire">Directive</a></h2>
|
||
<table class="directive">
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||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The default duration to cache a document when no expiry date is specified.</td></tr>
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||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDefaultExpire <var>seconds</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDefaultExpire 3600 (one hour)</code></td></tr>
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||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
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||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>The <code class="directive">CacheDefaultExpire</code> directive specifies a default time,
|
||
in seconds, to cache a document if neither an expiry date nor last-modified date are provided
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||
with the document. The value specified with the <code class="directive">CacheMaxExpire</code>
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||
directive does <em>not</em> override this setting.</p>
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||
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||
<div class="example"><p><code>
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||
CacheDefaultExpire 86400
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||
</code></p></div>
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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="CacheDisable" id="CacheDisable">CacheDisable</a> <a name="cachedisable" id="cachedisable">Directive</a></h2>
|
||
<table class="directive">
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||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Disable caching of specified URLs</td></tr>
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||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDisable <var> url-string</var></code></td></tr>
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||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
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||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>The <code class="directive">CacheDisable</code> directive instructs
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||
<code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> to <em>not</em> cache urls at or below
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||
<var>url-string</var>.</p>
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||
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<div class="example"><h3>Example</h3><p><code>
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CacheDisable /local_files
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</code></p></div>
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||
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<p> The <code>no-cache</code> environment variable can be set to
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||
disable caching on a finer grained set of resources in versions
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after 2.2.11.</p>
|
||
|
||
|
||
<h3>See also</h3>
|
||
<ul>
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||
<li><a href="../env.html">Environment Variables in Apache</a></li>
|
||
</ul>
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheEnable" id="CacheEnable">CacheEnable</a> <a name="cacheenable" id="cacheenable">Directive</a></h2>
|
||
<table class="directive">
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||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable caching of specified URLs using a specified storage
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||
manager</td></tr>
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||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheEnable <var>cache_type</var> <var>url-string</var></code></td></tr>
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||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>The <code class="directive">CacheEnable</code> directive instructs
|
||
<code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> to cache urls at or below
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||
<var>url-string</var>. The cache storage manager is specified with the
|
||
<var>cache_type</var> argument.
|
||
<var>cache_type</var> <code>disk</code> instructs
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||
<code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> to use the disk based storage manager
|
||
implemented by <code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code>.</p>
|
||
<p>In the event that the URL space overlaps between different
|
||
<code class="directive">CacheEnable</code> directives (as in the example below),
|
||
each possible storage manager will be run until the first one that
|
||
actually processes the request. The order in which the storage managers are
|
||
run is determined by the order of the <code class="directive">CacheEnable</code>
|
||
directives in the configuration file.</p>
|
||
|
||
<p>When acting as a forward proxy server, <var>url-string</var> can
|
||
also be used to specify remote sites and proxy protocols which
|
||
caching should be enabled for.</p>
|
||
|
||
<div class="example"><p><code>
|
||
# Cache proxied url's<br />
|
||
CacheEnable disk /<br /><br />
|
||
# Cache FTP-proxied url's<br />
|
||
CacheEnable disk ftp://<br /><br />
|
||
# Cache content from www.apache.org<br />
|
||
CacheEnable disk http://www.apache.org/<br />
|
||
</code></p></div>
|
||
|
||
<p> The <code>no-cache</code> environment variable can be set to
|
||
disable caching on a finer grained set of resources in versions
|
||
after 2.2.11.</p>
|
||
|
||
|
||
<h3>See also</h3>
|
||
<ul>
|
||
<li><a href="../env.html">Environment Variables in Apache</a></li>
|
||
</ul>
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheIgnoreCacheControl" id="CacheIgnoreCacheControl">CacheIgnoreCacheControl</a> <a name="cacheignorecachecontrol" id="cacheignorecachecontrol">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Ignore request to not serve cached content to client</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheIgnoreCacheControl On|Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheIgnoreCacheControl Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>Ordinarily, requests containing a Cache-Control: no-cache or
|
||
Pragma: no-cache header value will not be served from the cache. The
|
||
<code class="directive">CacheIgnoreCacheControl</code> directive allows this
|
||
behavior to be overridden. <code class="directive">CacheIgnoreCacheControl On</code>
|
||
tells the server to attempt to serve the resource from the cache even
|
||
if the request contains no-cache header values. Resources requiring
|
||
authorization will <em>never</em> be cached.</p>
|
||
|
||
<div class="example"><p><code>
|
||
CacheIgnoreCacheControl On
|
||
</code></p></div>
|
||
|
||
<div class="warning"><h3>Warning:</h3>
|
||
This directive will allow serving from the cache even if the client has
|
||
requested that the document not be served from the cache. This might
|
||
result in stale content being served.
|
||
</div>
|
||
|
||
<h3>See also</h3>
|
||
<ul>
|
||
<li><code class="directive"><a href="#cachestoreprivate">CacheStorePrivate</a></code></li>
|
||
<li><code class="directive"><a href="#cachestorenostore">CacheStoreNoStore</a></code></li>
|
||
</ul>
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheIgnoreHeaders" id="CacheIgnoreHeaders">CacheIgnoreHeaders</a> <a name="cacheignoreheaders" id="cacheignoreheaders">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Do not store the given HTTP header(s) in the cache.
|
||
</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheIgnoreHeaders <var>header-string</var> [<var>header-string</var>] ...</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheIgnoreHeaders None</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>According to RFC 2616, hop-by-hop HTTP headers are not stored in
|
||
the cache. The following HTTP headers are hop-by-hop headers and thus
|
||
do not get stored in the cache in <em>any</em> case regardless of the
|
||
setting of <code class="directive">CacheIgnoreHeaders</code>:</p>
|
||
|
||
<ul>
|
||
<li><code>Connection</code></li>
|
||
<li><code>Keep-Alive</code></li>
|
||
<li><code>Proxy-Authenticate</code></li>
|
||
<li><code>Proxy-Authorization</code></li>
|
||
<li><code>TE</code></li>
|
||
<li><code>Trailers</code></li>
|
||
<li><code>Transfer-Encoding</code></li>
|
||
<li><code>Upgrade</code></li>
|
||
</ul>
|
||
|
||
<p><code class="directive">CacheIgnoreHeaders</code> specifies additional HTTP
|
||
headers that should not to be stored in the cache. For example, it makes
|
||
sense in some cases to prevent cookies from being stored in the cache.</p>
|
||
|
||
<p><code class="directive">CacheIgnoreHeaders</code> takes a space separated list
|
||
of HTTP headers that should not be stored in the cache. If only hop-by-hop
|
||
headers not should be stored in the cache (the RFC 2616 compliant
|
||
behaviour), <code class="directive">CacheIgnoreHeaders</code> can be set to
|
||
<code>None</code>.</p>
|
||
|
||
<div class="example"><h3>Example 1</h3><p><code>
|
||
CacheIgnoreHeaders Set-Cookie
|
||
</code></p></div>
|
||
|
||
<div class="example"><h3>Example 2</h3><p><code>
|
||
CacheIgnoreHeaders None
|
||
</code></p></div>
|
||
|
||
<div class="warning"><h3>Warning:</h3>
|
||
If headers like <code>Expires</code> which are needed for proper cache
|
||
management are not stored due to a
|
||
<code class="directive">CacheIgnoreHeaders</code> setting, the behaviour of
|
||
mod_cache is undefined.
|
||
</div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheIgnoreNoLastMod" id="CacheIgnoreNoLastMod">CacheIgnoreNoLastMod</a> <a name="cacheignorenolastmod" id="cacheignorenolastmod">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Ignore the fact that a response has no Last Modified
|
||
header.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheIgnoreNoLastMod On|Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheIgnoreNoLastMod Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>Ordinarily, documents without a last-modified date are not cached.
|
||
Under some circumstances the last-modified date is removed (during
|
||
<code class="module"><a href="../mod/mod_include.html">mod_include</a></code> processing for example) or not provided
|
||
at all. The <code class="directive">CacheIgnoreNoLastMod</code> directive
|
||
provides a way to specify that documents without last-modified dates
|
||
should be considered for caching, even without a last-modified date.
|
||
If neither a last-modified date nor an expiry date are provided with
|
||
the document then the value specified by the
|
||
<code class="directive">CacheDefaultExpire</code> directive will be used to
|
||
generate an expiration date.</p>
|
||
|
||
<div class="example"><p><code>
|
||
CacheIgnoreNoLastMod On
|
||
</code></p></div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheIgnoreQueryString" id="CacheIgnoreQueryString">CacheIgnoreQueryString</a> <a name="cacheignorequerystring" id="cacheignorequerystring">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Ignore query string when caching</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheIgnoreQueryString On|Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheIgnoreQueryString Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>Ordinarily, requests with query string parameters are cached separately
|
||
for each unique query string. This is according to RFC 2616/13.9 done only
|
||
if an expiration time is specified. The
|
||
<code class="directive">CacheIgnoreQueryString</code> directive tells the cache to
|
||
cache requests even if no expiration time is specified, and to reply with
|
||
a cached reply even if the query string differs. From a caching point of
|
||
view the request is treated as if having no query string when this
|
||
directive is enabled.</p>
|
||
|
||
<div class="example"><p><code>
|
||
CacheIgnoreQueryString On
|
||
</code></p></div>
|
||
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheIgnoreURLSessionIdentifiers" id="CacheIgnoreURLSessionIdentifiers">CacheIgnoreURLSessionIdentifiers</a> <a name="cacheignoreurlsessionidentifiers" id="cacheignoreurlsessionidentifiers">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Ignore defined session identifiers encoded in the URL when caching
|
||
</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheIgnoreURLSessionIdentifiers <var>identifier</var> [<var>identifier</var>] ...</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheIgnoreURLSessionIdentifiers None</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>Sometimes applications encode the session identifier into the URL like in the following
|
||
Examples:
|
||
</p>
|
||
<ul>
|
||
<li><code>/someapplication/image.gif;jsessionid=123456789</code></li>
|
||
<li><code>/someapplication/image.gif?PHPSESSIONID=12345678</code></li>
|
||
</ul>
|
||
<p>This causes cachable resources to be stored separately for each session, which
|
||
is often not desired. <code class="directive">CacheIgnoreURLSessionIdentifiers</code> lets
|
||
define a list of identifiers that are removed from the key that is used to identify
|
||
an entity in the cache, such that cachable resources are not stored separately for
|
||
each session.
|
||
</p>
|
||
<p><code>CacheIgnoreURLSessionIdentifiers None</code> clears the list of ignored
|
||
identifiers. Otherwise, each identifier is added to the list.</p>
|
||
|
||
<div class="example"><h3>Example 1</h3><p><code>
|
||
CacheIgnoreURLSessionIdentifiers jsessionid
|
||
</code></p></div>
|
||
|
||
<div class="example"><h3>Example 2</h3><p><code>
|
||
CacheIgnoreURLSessionIdentifiers None
|
||
</code></p></div>
|
||
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheLastModifiedFactor" id="CacheLastModifiedFactor">CacheLastModifiedFactor</a> <a name="cachelastmodifiedfactor" id="cachelastmodifiedfactor">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The factor used to compute an expiry date based on the
|
||
LastModified date.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheLastModifiedFactor <var>float</var></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheLastModifiedFactor 0.1</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>In the event that a document does not provide an expiry date but does
|
||
provide a last-modified date, an expiry date can be calculated based on
|
||
the time since the document was last modified. The
|
||
<code class="directive">CacheLastModifiedFactor</code> directive specifies a
|
||
<var>factor</var> to be used in the generation of this expiry date
|
||
according to the following formula:
|
||
|
||
<code>expiry-period = time-since-last-modified-date * <var>factor</var>
|
||
expiry-date = current-date + expiry-period</code>
|
||
|
||
For example, if the document was last modified 10 hours ago, and
|
||
<var>factor</var> is 0.1 then the expiry-period will be set to
|
||
10*0.1 = 1 hour. If the current time was 3:00pm then the computed
|
||
expiry-date would be 3:00pm + 1hour = 4:00pm.
|
||
|
||
If the expiry-period would be longer than that set by
|
||
<code class="directive">CacheMaxExpire</code>, then the latter takes
|
||
precedence.</p>
|
||
|
||
<div class="example"><p><code>
|
||
CacheLastModifiedFactor 0.5
|
||
</code></p></div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheLock" id="CacheLock">CacheLock</a> <a name="cachelock" id="cachelock">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable the thundering herd lock.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheLock <var>on|off</var></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheLock off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>The <code class="directive">CacheLock</code> directive enables the thundering herd lock
|
||
for the given URL space.</p>
|
||
|
||
<p>In a minimal configuration the following directive is all that is needed to
|
||
enable the thundering herd lock in the default system temp directory.</p>
|
||
|
||
<div class="example"><p><code>
|
||
# Enable chache lock<br />
|
||
CacheLock on<br /><br />
|
||
</code></p></div>
|
||
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheLockMaxAge" id="CacheLockMaxAge">CacheLockMaxAge</a> <a name="cachelockmaxage" id="cachelockmaxage">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Set the maximum possible age of a cache lock.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheLockMaxAge <var>integer</var></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheLockMaxAge 5</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>The <code class="directive">CacheLockMaxAge</code> directive specifies the maximum
|
||
age of any cache lock.</p>
|
||
|
||
<p>A lock older than this value in seconds will be ignored, and the next
|
||
incoming request will be given the opportunity to re-establish the lock.
|
||
This mechanism prevents a slow client taking an excessively long time to refresh
|
||
an entity.</p>
|
||
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheLockPath" id="CacheLockPath">CacheLockPath</a> <a name="cachelockpath" id="cachelockpath">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Set the lock path directory.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheLockPath <var>directory</var></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheLockPath /tmp/mod_cache-lock</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>The <code class="directive">CacheLockPath</code> directive allows you to specify the
|
||
directory in which the locks are created. By default, the system's temporary
|
||
folder is used. Locks consist of empty files that only exist for stale URLs
|
||
in flight, so is significantly less resource intensive than the traditional
|
||
disk cache.</p>
|
||
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheMaxExpire" id="CacheMaxExpire">CacheMaxExpire</a> <a name="cachemaxexpire" id="cachemaxexpire">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum time in seconds to cache a document</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMaxExpire <var>seconds</var></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMaxExpire 86400 (one day)</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>The <code class="directive">CacheMaxExpire</code> directive specifies the maximum number of
|
||
seconds for which cachable HTTP documents will be retained without checking the origin
|
||
server. Thus, documents will be out of date at most this number of seconds. This maximum
|
||
value is enforced even if an expiry date was supplied with the document.</p>
|
||
|
||
<div class="example"><p><code>
|
||
CacheMaxExpire 604800
|
||
</code></p></div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheMinExpire" id="CacheMinExpire">CacheMinExpire</a> <a name="cacheminexpire" id="cacheminexpire">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum time in seconds to cache a document</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMinExpire <var>seconds</var></code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMinExpire 0</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>The <code class="directive">CacheMinExpire</code> directive specifies the minimum number of
|
||
seconds for which cachable HTTP documents will be retained without checking the origin
|
||
server. This is only used if no valid expire time was supplied with the document.</p>
|
||
|
||
|
||
<div class="example"><p><code>
|
||
CacheMinExpire 3600
|
||
</code></p></div>
|
||
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheStoreNoStore" id="CacheStoreNoStore">CacheStoreNoStore</a> <a name="cachestorenostore" id="cachestorenostore">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Attempt to cache requests or responses that have been marked as no-store.</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheStoreNoStore On|Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheStoreNoStore Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>Ordinarily, requests or responses with Cache-Control: no-store header
|
||
values will not be stored in the cache. The
|
||
<code class="directive">CacheStoreNoCache</code> directive allows this
|
||
behavior to be overridden. <code class="directive">CacheStoreNoCache</code> On
|
||
tells the server to attempt to cache the resource even if it contains
|
||
no-store header values. Resources requiring authorization will
|
||
<em>never</em> be cached.</p>
|
||
|
||
<div class="example"><p><code>
|
||
CacheStoreNoStore On
|
||
</code></p></div>
|
||
|
||
<div class="warning"><h3>Warning:</h3>
|
||
As described in RFC 2616, the no-store directive is intended to
|
||
"prevent the inadvertent release or retention of sensitive information
|
||
(for example, on backup tapes)." Enabling this option could store
|
||
sensitive information in the cache. You are hereby warned.
|
||
</div>
|
||
|
||
<h3>See also</h3>
|
||
<ul>
|
||
<li><code class="directive"><a href="#cacheignorecachecontrol">CacheIgnoreCacheControl</a></code></li>
|
||
<li><code class="directive"><a href="#cachestoreprivate">CacheStorePrivate</a></code></li>
|
||
</ul>
|
||
</div>
|
||
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
|
||
<div class="directive-section"><h2><a name="CacheStorePrivate" id="CacheStorePrivate">CacheStorePrivate</a> <a name="cachestoreprivate" id="cachestoreprivate">Directive</a></h2>
|
||
<table class="directive">
|
||
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Attempt to cache responses that the server has marked as private</td></tr>
|
||
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheStorePrivate On|Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheStorePrivate Off</code></td></tr>
|
||
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
|
||
<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
|
||
<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_cache</td></tr>
|
||
</table>
|
||
<p>Ordinarily, responses with Cache-Control: private header values will not
|
||
be stored in the cache. The <code class="directive">CacheStorePrivate</code>
|
||
directive allows this behavior to be overridden.
|
||
<code class="directive">CacheStorePrivate</code> On
|
||
tells the server to attempt to cache the resource even if it contains
|
||
private header values. Resources requiring authorization will
|
||
<em>never</em> be cached.</p>
|
||
|
||
<div class="example"><p><code>
|
||
CacheStorePrivate On
|
||
</code></p></div>
|
||
|
||
<div class="warning"><h3>Warning:</h3>
|
||
This directive will allow caching even if the upstream server has
|
||
requested that the resource not be cached. This directive is only
|
||
ideal for a 'private' cache.
|
||
</div>
|
||
|
||
<h3>See also</h3>
|
||
<ul>
|
||
<li><code class="directive"><a href="#cacheignorecachecontrol">CacheIgnoreCacheControl</a></code></li>
|
||
<li><code class="directive"><a href="#cachestorenostore">CacheStoreNoStore</a></code></li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
<div class="bottomlang">
|
||
<p><span>Available Languages: </span><a href="../en/mod/mod_cache.html" title="English"> en </a> |
|
||
<a href="../ja/mod/mod_cache.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
|
||
<a href="../ko/mod/mod_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
|
||
</div><div id="footer">
|
||
<p class="apache">Copyright 2009 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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