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apache/docs/manual/mod/mod_disk_cache.html.en
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<title>mod_disk_cache - Apache HTTP Server</title>
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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>
<p class="apache">Apache HTTP Server Version 2.3</p>
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<div id="page-content">
<div id="preamble"><h1>Apache Module mod_disk_cache</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/mod/mod_disk_cache.html" title="English">&nbsp;en&nbsp;</a> |
<a href="../fr/mod/mod_disk_cache.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
<a href="../ja/mod/mod_disk_cache.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
<a href="../ko/mod/mod_disk_cache.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
</div>
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Content cache storage manager keyed to URIs</td></tr>
<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>disk_cache_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_disk_cache.c</td></tr></table>
<h3>Summary</h3>
<p><code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code> implements a disk based storage
manager. It is primarily of use in conjunction with
<code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>.</p>
<p>Content is stored in and retrieved from the cache using URI based
keys. Content with access protection is not cached.</p>
<p><code class="program"><a href="../programs/htcacheclean.html">htcacheclean</a></code> can be used to maintain the cache
size at a maximum level.</p>
<div class="note"><h3>Note:</h3>
<p><code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code> requires the services of
<code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>.</p>
</div>
<div class="note"><h3>Note:</h3>
<p><code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code> uses the sendfile feature to
serve files from the cache when supported by the platform, and
when enabled with <code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code>.
However, per-directory and .htaccess configuration of
<code class="directive"><a href="../mod/core.html#enablesendfile">EnableSendfile</a></code> are ignored by
<code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code> as the corresponding settings are not
available to the module when a request is being served from the
cache.</p>
</div>
</div>
<div id="quickview"><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/down.gif" /> <a href="#cachedirlength">CacheDirLength</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#cachedirlevels">CacheDirLevels</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#cachemaxfilesize">CacheMaxFileSize</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#cacheminfilesize">CacheMinFileSize</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#cachereadsize">CacheReadSize</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#cachereadtime">CacheReadTime</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#cacheroot">CacheRoot</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="CacheDirLength" id="CacheDirLength">CacheDirLength</a> <a name="cachedirlength" id="cachedirlength">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of characters in subdirectory names</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLength <var>length</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLength 2</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_disk_cache</td></tr>
</table>
<p>The <code class="directive">CacheDirLength</code> directive sets the number
of characters for each subdirectory name in the cache hierarchy. It can
be used in conjunction with <code class="directive">CacheDirLevels</code> to
determine the approximate structure of your cache hierarchy.</p>
<p>A high value for <code class="directive">CacheDirLength</code> combined
with a low value for <code class="directive">CacheDirLevels</code> will result in
a relatively flat hierarchy, with a large number of subdirectories at each
level.</p>
<div class="note">
<p>The result of <code class="directive"><a href="#cachedirlevels">CacheDirLevels</a></code>* <code class="directive">CacheDirLength</code>
must not be higher than 20.</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="CacheDirLevels" id="CacheDirLevels">CacheDirLevels</a> <a name="cachedirlevels" id="cachedirlevels">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The number of levels of subdirectories in the
cache.</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDirLevels <var>levels</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDirLevels 2</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_disk_cache</td></tr>
</table>
<p>The <code class="directive">CacheDirLevels</code> directive sets the number
of subdirectory levels in the cache. Cached data will be saved this
many directory levels below the <code class="directive"><a href="#cacheroot">CacheRoot</a></code> directory.</p>
<p>A high value for <code class="directive">CacheDirLevels</code> combined
with a low value for <code class="directive">CacheDirLength</code> will result in
a relatively deep hierarchy, with a small number of subdirectories at each
level.</p>
<div class="note">
<p>The result of <code class="directive">CacheDirLevels</code>*
<code class="directive"><a href="#cachedirlength">CacheDirLength</a></code> must
not be higher than 20.</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="CacheMaxFileSize" id="CacheMaxFileSize">CacheMaxFileSize</a> <a name="cachemaxfilesize" id="cachemaxfilesize">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The maximum size (in bytes) of a document to be placed in the
cache</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMaxFileSize <var>bytes</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMaxFileSize 1000000</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_disk_cache</td></tr>
</table>
<p>The <code class="directive">CacheMaxFileSize</code> directive sets the
maximum size, in bytes, for a document to be considered for storage in
the cache.</p>
<div class="example"><p><code>
CacheMaxFileSize 64000
</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="CacheMinFileSize" id="CacheMinFileSize">CacheMinFileSize</a> <a name="cacheminfilesize" id="cacheminfilesize">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum size (in bytes) of a document to be placed in the
cache</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheMinFileSize <var>bytes</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheMinFileSize 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_disk_cache</td></tr>
</table>
<p>The <code class="directive">CacheMinFileSize</code> directive sets the
minimum size, in bytes, for a document to be considered for storage
in the cache.</p>
<div class="example"><p><code>
CacheMinFileSize 64
</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="CacheReadSize" id="CacheReadSize">CacheReadSize</a> <a name="cachereadsize" id="cachereadsize">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum size (in bytes) of the document to read and be cached
before sending the data downstream</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadSize <var>bytes</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadSize 0</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</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_disk_cache</td></tr>
</table>
<p>The <code class="directive">CacheReadSize</code> directive sets the
minimum amount of data, in bytes, to be read from the backend before the
data is sent to the client. The default of zero causes all data read of
any size to be passed downstream to the client immediately as it arrives.
Setting this to a higher value causes the disk cache to buffer at least
this amount before sending the result to the client. This can improve
performance when caching content from a reverse proxy.</p>
<p>This directive only takes effect when the data is being saved to the
cache, as opposed to data being served from the cache.</p>
<div class="example"><p><code>
CacheReadSize 102400
</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="CacheReadTime" id="CacheReadTime">CacheReadTime</a> <a name="cachereadtime" id="cachereadtime">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The minimum time (in milliseconds) that should elapse while reading
before data is sent downstream</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheReadTime <var>milliseconds</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheReadTime 0</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</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_disk_cache</td></tr>
</table>
<p>The <code class="directive">CacheReadTime</code> directive sets the minimum amount
of elapsed time that should pass before making an attempt to send data
downstream to the client. During the time period, data will be buffered
before sending the result to the client. This can improve performance when
caching content from a reverse proxy.</p>
<p>The default of zero disables this option.</p>
<p>This directive only takes effect when the data is being saved to the
cache, as opposed to data being served from the cache. It is recommended
that this option be used alongside the
<code class="directive"><a href="#cachereadsize">CacheReadSize</a></code> directive to
ensure that the server does not buffer excessively should data arrive faster
than expected.</p>
<div class="example"><p><code>
CacheReadTime 1000
</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="CacheRoot" id="CacheRoot">CacheRoot</a> <a name="cacheroot" id="cacheroot">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The directory root under which cache files are
stored</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheRoot <var>directory</var></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_disk_cache</td></tr>
</table>
<p>The <code class="directive">CacheRoot</code> directive defines the name of
the directory on the disk to contain cache files. If the <code class="module"><a href="../mod/mod_disk_cache.html">mod_disk_cache</a></code> module has been loaded or compiled in to the
Apache server, this directive <em>must</em> be defined. Failing to
provide a value for <code class="directive">CacheRoot</code> will result in
a configuration file processing error. The <code class="directive"><a href="#cachedirlevels">CacheDirLevels</a></code> and <code class="directive"><a href="#cachedirlength">CacheDirLength</a></code> directives define
the structure of the directories under the specified root directory.</p>
<div class="example"><p><code>
CacheRoot c:/cacheroot
</code></p></div>
</div>
</div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="../en/mod/mod_disk_cache.html" title="English">&nbsp;en&nbsp;</a> |
<a href="../fr/mod/mod_disk_cache.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
<a href="../ja/mod/mod_disk_cache.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
<a href="../ko/mod/mod_disk_cache.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
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