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<title>mod_cache - Apache HTTP Server</title>
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<p class="apache">Apache HTTP Server Version 2.1</p>
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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-project/">Documentation</a> > <a href="../">Version 2.1</a> > <a href="./">Modules</a></div>
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<div id="preamble"><h1>Apache Module mod_cache</h1>
<div class="toplang">
<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>
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Content cache keyed to URIs.</td></tr>
<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>cache_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>mod_cache.c</td></tr></table>
<h3>Summary</h3>
<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
content cache that can be used to cache either local or proxied content.
<code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> requires the services of one or more storage
management modules. Two storage management modules are included in
the base Apache distribution:</p>
<dl>
<dd>implements a disk based storage manager.</dd>
<dd>implements a memory based storage manager.
<code class="module"><a href="/mod/mod_mem_cache.html">mod_mem_cache</a></code> can be configured to operate in two
modes: caching open file descriptors or caching objects in heap storage.
<code class="module"><a href="/mod/mod_mem_cache.html">mod_mem_cache</a></code> can be used to cache locally generated content
or to cache backend server content for <code class="module"><a href="/mod/mod_proxy.html">mod_proxy</a></code> when
configured using <code class="directive"><a href="/mod/mod_proxy.html#proxypass">ProxyPass</a></code>
(aka <dfn>reverse proxy</dfn>)</dd>
</dl>
<p>Content is stored in and retrieved from the cache using URI based keys. Content with
access protection is not cached.</p>
</div>
<div id="quickview"><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="/images/down.gif" /> <a href="#cacheignorecachecontrol">CacheIgnoreCacheControl</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#cacheignorenolastmod">CacheIgnoreNoLastMod</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#cachelastmodifiedfactor">CacheLastModifiedFactor</a></li>
</ul>
<h3>Topics</h3>
<ul id="topics">
<li><img alt="" src="/images/down.gif" /> <a href="#related">Related Modules and Directives</a></li>
</ul></div>
<div class="section">
<h2><a name="related" id="related">Related Modules and Directives</a></h2>
<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><li><code class="module"><a href="/mod/mod_mem_cache.html">mod_mem_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#cachesize">CacheSize</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><li><code class="directive"><a href="/mod/mod_mem_cache.html#mcachesize">MCacheSize</a></code></li><li><code class="directive"><a href="/mod/mod_mem_cache.html#mcachemaxobjectcount">MCacheMaxObjectCount</a></code></li><li><code class="directive"><a href="/mod/mod_mem_cache.html#mcacheminobjectsize">MCacheMinObjectSize</a></code></li><li><code class="directive"><a href="/mod/mod_mem_cache.html#mcachemaxobjectsize">MCacheMaxObjectSize</a></code></li><li><code class="directive"><a href="/mod/mod_mem_cache.html#mcacheremovalalgorithm">MCacheRemovalAlgorithm</a></code></li><li><code class="directive"><a href="/mod/mod_mem_cache.html#mcachemaxstreamingbuffer">MCacheMaxStreamingBuffer</a></code></li></ul></td></tr></table>
<div class="section">
<h2><a name="sampleconf" id="sampleconf">Sample Configuration</a></h2>
#<br />
# Sample Cache Configuration<br />
#<br />
<br />
<IfModule mod_cache.c><br />
<span class="indent">
# If you want to use mod_disk_cache instead of mod_mem_cache,<br />
# uncomment the line above and comment out the LoadModule line below.<br />
<IfModule mod_disk_cache.c><br />
<span class="indent">
CacheRoot c:/cacheroot<br />
CacheEnable disk /<br />
CacheDirLevels 5<br />
CacheDirLength 3<br />
</span>
</IfModule> <br />
<br />
<IfModule mod_mem_cache.c><br />
<span class="indent">
CacheEnable mem /<br />
MCacheSize 4096<br />
MCacheMaxObjectCount 100<br />
MCacheMinObjectSize 1<br />
MCacheMaxObjectSize 2048<br />
</span>
</IfModule><br />
<br />
# When acting as a proxy, don't cache the list of security updates<br />
CacheDisable http://security.update.server/update-list/<br />
</span>
</IfModule>
</code></p></div>
</div>
<div class="directive-section"><h2><a name="CacheDefaultExpire" id="CacheDefaultExpire">CacheDefaultExpire</a> <a name="cachedefaultexpire" id="cachedefaultexpire">Directive</a></h2>
<table class="directive">
<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>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDefaultExpire <var>seconds</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheDefaultExpire 3600 (one hour)</code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</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
with the document. The value specified with the <code class="directive">CacheMaxExpire</code>
directive does <em>not</em> override this setting.</p>
<div class="example"><p><code>
CacheDefaultExpire 86400
</code></p></div>
</div>
<div class="directive-section"><h2><a name="CacheDisable" id="CacheDisable">CacheDisable</a> <a name="cachedisable" id="cachedisable">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Disable caching of specified URLs</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheDisable <var> url-string</var></code></td></tr>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>The <code class="directive">CacheDisable</code> directive instructs
<code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> to <em>not</em> cache urls at or below
<var>url-string</var>.</p>
<div class="example"><h3>Example</h3><p><code>
CacheDisable /local_files
</code></p></div>
</div>
<div class="directive-section"><h2><a name="CacheEnable" id="CacheEnable">CacheEnable</a> <a name="cacheenable" id="cacheenable">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enable caching of specified URLs using a specified storage
manager</td></tr>
<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>
<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
</table>
<p>The <code class="directive">CacheEnable</code> directive instructs
<var>url-string</var>. The cache storage manager is specified with the
<var>cache_type</var> argument. <var>cache_type</var> <code> mem</code>
instructs <code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> to use the memory based storage
manager implemented by <code class="module"><a href="/mod/mod_mem_cache.html">mod_mem_cache</a></code>.
<var>cache_type</var> <code>disk</code> instructs
<code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> to use the disk based storage manager
<var>cache_type</var> <code>fd</code> instructs
<code class="module"><a href="/mod/mod_cache.html">mod_cache</a></code> to use the file descriptor cache implemented
<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>
<div class="example"><p><code>
CacheEnable mem /manual<br />
CacheEnable fd /images<br />
CacheEnable disk /<br />
</code></p></div>
<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>
</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>
</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</code>
On 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="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>
</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="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>
</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="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>
</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="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>
</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="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>
</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="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>
</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 1995-2005 The Apache Software Foundation or its licensors, as applicable.<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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