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<modulesynopsis>

<name>mod_cache</name>

<description>Content cache keyed to URIs.</description>

<status>Experimental</status>

<sourcefile>mod_cache.c</sourcefile>

<identifier>cache_module</identifier>

<summary>

<note type="warning">

This module is experimental. Documentation is still under development...

</note>

<p><module>mod_cache</module> 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.

<module>mod_cache</module> requires the services of one or more storage

management modules. Two storage management modules are included in

the base Apache distribution:</p>

<dl>

<dt><module>mod_disk_cache</module></dt>

<dd>implements a disk based storage manager for use with

<module>mod_proxy</module></dd>

<dt><module>mod_mem_cache</module></dt>

<dd>implements an in-memory based storage manager.

<module>mod_mem_cache</module> can be configured to operate in two

modes: caching open file descriptors or caching objects in heap storage.

<module>mod_mem_cache</module> is most useful when used to cache

locally generated content or to cache backend server content for

<module>mod_proxy</module> configured for <directive module="mod_proxy"

>ProxyPass</directive> (aka <dfn>reverse proxy</dfn>)</dd>

</dl>

<p>Content stored and retrived keyed to the URL. Content with

access protections is not cached.</p>

</summary>

<section id="related"><title>Related Modules and Directives</title>

<related>

<modulelist>

<module>mod_disk_cache</module>

<module>mod_mem_cache</module>

</modulelist>

<directivelist>

<directive module="mod_disk_cache">CacheRoot</directive>

<directive module="mod_disk_cache">CacheSize</directive>

<directive module="mod_disk_cache">CacheGcInterval</directive>

<directive module="mod_disk_cache">CacheDirLevels</directive>

<directive module="mod_disk_cache">CacheDirLength</directive>

<directive module="mod_disk_cache">CacheExpiryCheck</directive>

<directive module="mod_disk_cache">CacheMinFileSize</directive>

<directive module="mod_disk_cache">CacheMaxFileSize</directive>

<directive module="mod_disk_cache">CacheTimeMargin</directive>

<directive module="mod_disk_cache">CacheGcDaily</directive>

<directive module="mod_disk_cache">CacheGcUnused</directive>

<directive module="mod_disk_cache">CacheGcClean</directive>

<directive module="mod_disk_cache">CacheGcMemUsage</directive>

<directive module="mod_mem_cache">MCacheSize</directive>

<directive module="mod_mem_cache">MCacheMaxObjectCount</directive>

<directive module="mod_mem_cache">MCacheMinObjectSize</directive>

<directive module="mod_mem_cache">MCacheMaxObjectSize</directive>

<directive module="mod_mem_cache">MCacheRemovalAlgorithm</directive>

</directivelist>

</related>

</section>

<section id="sampleconf"><title>Sample Configuration</title>

<example><title>Sample httpd.conf</title>

#<br />

# Sample Cache Configuration<br />

#<br />

LoadModule cache_module modules/mod_cache.so<br />

<br />

&lt;IfModule mod_cache.c&gt;<br />

<indent>

#LoadModule disk_cache_module modules/mod_disk_cache.so<br />

&lt;IfModule mod_disk_cache.c&gt;<br />

<indent>

CacheRoot c:/cacheroot<br />

CacheSize 256<br />

CacheEnable disk /<br />

CacheDirLevels 5<br />

CacheDirLength 3<br />

</indent>

&lt;/IfModule&gt; <br />

<br />

LoadModule mem_cache_module modules/mod_mem_cache.so<br />

&lt;IfModule mod_mem_cache.c&gt;<br />

<indent>

MCacheEnable mem /<br />

MCacheSize 4096<br />

MCacheMaxObjectCount 100<br />

MCacheMinObjectSize 1<br />

MCacheMaxObjectSize 2048<br />

</indent>

&lt;/IfModule&gt;<br />

</indent>

&lt;/IfModule&gt;

</example>

</section>

<directivesynopsis>

<name>CacheEnable</name>

<description>Enable caching specified URLs in a specified storage

manager</description>

<syntax>CacheEnable <var>cache_type</var> <var>url-string</var></syntax>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>The <directive>CacheEnable</directive> directive instructs

<module>mod_cache</module> to cache urls at or below

<var>url-string</var>. The cache store is specified with the

<var>cache_type</var> argument. <var>cache_type</var> <code>mem</code>

instructs <module>mod_cache</module> to use the in-memory cache storage

manager implemented by <module>mod_mem_cache</module>.

<var>cache_type</var> <code>disk</code> instructs

<module>mod_cache</module> to use the cache storage manager implemented

by <module>mod_disk_cache</module>.</p>

<example>

CacheEnable disk /<br />

CacheEnable mem /manual<br />

CacheEnable fd /images<br />

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheDisable</name>

<description>Disable caching of specified URLs by specified storage

manager</description>

<syntax>CacheDisable <var>cache_type</var> <var>url-string</var></syntax>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>The <directive>CacheDisable</directive> directive instructs

<module>mod_cache</module> to <em>not</em> cache urls at or below

<var>url-string</var>.</p>

<example><title>Example</title>

CacheDisable disk /local_files

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheMaxExpire</name>

<description>The maximum time in seconds to cache a document</description>

<syntax>CacheMaxExpire <var>seconds</var></syntax>

<default>CacheMaxExpire 86400 (one day)</default>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>The maximum time in seconds to cache a document. The

<directive>CacheMaxExpire</directive> takes precedence over the

<code>Expires</code> field from the header.</p>

<example>

CacheMaxExpire 604800

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheDefaultExpire</name>

<description>The default time in seconds to cache a document</description>

<syntax>CacheDefaultExpire <var>seconds</var></syntax>

<default>CacheDefaultExpire 3600 (one hour)</default>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>The default time in seconds to cache a document if the page does not have

an expiry date in the <code>Expires</code> field.</p>

<example>

CacheDefaultExpire 86400

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheIgnoreNoLastMod</name>

<description>Ignore responses where there is no Last Modified

Header</description>

<syntax>CacheIgnoreNoLastMod On|Off</syntax>

<default>CacheIgnoreNoLastMod Off</default>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>Ignore responses where there is no Last Modified Header.</p>

<example>

CacheIgnoreNoLastMod On

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheIgnoreCacheControl</name>

<description>Ignore requests from the client for uncached

content</description>

<syntax>CacheIgnoreCacheControl On|Off</syntax>

<default>CacheIgnoreCacheControl Off</default>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>Ignore requests from the client for uncached content</p>

<example>

CacheIgnoreCacheControl On

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheLastModifiedFactor</name>

<description>The factor used to estimate the Expires date from the

LastModified date</description>

<syntax>CacheLastModifiedFactor <var>float</var></syntax>

<default>CacheLastModifiedFactor 0.1</default>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>The factor used to estimate the Expires date from the LastModified date.</p>

<example>

CacheLastModifiedFactor 0.5

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheForceCompletion</name>

<description>Percentage of download to arrive for the cache to force

complete transfer</description>

<syntax>CacheForceCompletion <var>Percentage</var></syntax>

<default>CacheForceCompletion 60</default>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>Percentage of download to arrive for the cache to force complete transfer.</p>

<example>

CacheForceCompletion 80

</example>

<note type="warning">

This feature is currently <em>not</em> implemented.

</note>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheMaxStreamingBuffer</name>

<description>Maximum amount of a streamed response to buffer in memory

before declaring the response uncacheable</description>

<syntax>CacheMaxStreamingBuffer <var>size_in_bytes</var></syntax>

<default>CacheMaxStreamingBuffer 0</default>

<contextlist><context>server config</context><context>virtual host</context>

</contextlist>

<usage>

<p>Maximum number of bytes of a streamed response (<em>i.e.</em>, a

response where the entire content is not available all at once, such

as a proxy or CGI response) to buffer before deciding if the response

is cacheable. By default, a streamed response will <em>not</em> be

cached unless it has a <code>Content-Length</code> header. The reason

for this is to avoid using a large amount of memory to buffer a partial

response that might end up being too large to fit in the cache anyway.

To enable caching of streamed responses, use <directive

>CacheMaxStreamingBuffer</directive> to specify the maximum amount of

buffer space to use per request.</p>

<note><title>Note:</title>

<p>Using a nonzero value for <directive

>CacheMaxStreamingBuffer</directive> will not delay the transmission

of the response to the client. As soon as <module>mod_cache</module>

copies a block of streamed content into a buffer, it sends the block

on to the next output filter for delivery to the client.</p>

</note>

<example>

# Enable caching of streamed responses up to 64KB:<br />

CacheMaxStreamingBuffer 65536

</example>

</usage>

</directivesynopsis>

</modulesynopsis>