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<modulesynopsis metafile="mod_disk_cache.xml.meta">

<name>mod_disk_cache</name>

<description>Content cache storage manager keyed to URIs</description>

<status>Extension</status>

<sourcefile>mod_disk_cache.c</sourcefile>

<identifier>disk_cache_module</identifier>

<summary>

<p><module>mod_disk_cache</module> implements a disk based storage

manager. It is primarily of use in conjunction with

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

<p>Content is stored in and retrieved from the cache using URI based

keys. Content with access protection is not cached.</p>

<p><program>htcacheclean</program> can be used to maintain the cache

size at a maximum level.</p>

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

<p><module>mod_disk_cache</module> requires the services of

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

</note>

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

<p><module>mod_disk_cache</module> uses the sendfile feature to

serve files from the cache when supported by the platform, and

when enabled with <directive module="core">EnableSendfile</directive>.

However, per-directory and .htaccess configuration of

<directive module="core">EnableSendfile</directive> are ignored by

<module>mod_disk_cache</module> as the corresponding settings are not

available to the module when a request is being served from the

cache.</p>

</note>

</summary>

<directivesynopsis>

<name>CacheRoot</name>

<description>The directory root under which cache files are

stored</description>

<syntax>CacheRoot <var>directory</var></syntax>

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

</contextlist>

<usage>

<p>The <directive>CacheRoot</directive> directive defines the name of

the directory on the disk to contain cache files. If the <module

>mod_disk_cache</module> module has been loaded or compiled in to the

Apache server, this directive <em>must</em> be defined. Failing to

provide a value for <directive>CacheRoot</directive> will result in

a configuration file processing error. The <directive

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

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

the structure of the directories under the specified root directory.</p>

<example>

CacheRoot c:/cacheroot

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheDirLevels</name>

<description>The number of levels of subdirectories in the

cache.</description>

<syntax>CacheDirLevels <var>levels</var></syntax>

<default>CacheDirLevels 2</default>

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

</contextlist>

<usage>

<p>The <directive>CacheDirLevels</directive> directive sets the number

of subdirectory levels in the cache. Cached data will be saved this

many directory levels below the <directive module="mod_disk_cache"

>CacheRoot</directive> directory.</p>

<p>A high value for <directive>CacheDirLevels</directive> combined

with a low value for <directive>CacheDirLength</directive> will result in

a relatively deep hierarchy, with a small number of subdirectories at each

level.</p>

<note>

<p>The result of <directive>CacheDirLevels</directive>*

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

not be higher than 20.</p>

</note>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheDirLength</name>

<description>The number of characters in subdirectory names</description>

<syntax>CacheDirLength <var>length</var></syntax>

<default>CacheDirLength 2</default>

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

</contextlist>

<usage>

<p>The <directive>CacheDirLength</directive> directive sets the number

of characters for each subdirectory name in the cache hierarchy. It can

be used in conjunction with <directive>CacheDirLevels</directive> to

determine the approximate structure of your cache hierarchy.</p>

<p>A high value for <directive>CacheDirLength</directive> combined

with a low value for <directive>CacheDirLevels</directive> will result in

a relatively flat hierarchy, with a large number of subdirectories at each

level.</p>

<note>

<p>The result of <directive module="mod_disk_cache"

>CacheDirLevels</directive>* <directive>CacheDirLength</directive>

must not be higher than 20.</p>

</note>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheMinFileSize</name>

<description>The minimum size (in bytes) of a document to be placed in the

cache</description>

<syntax>CacheMinFileSize <var>bytes</var></syntax>

<default>CacheMinFileSize 1</default>

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

</contextlist>

<usage>

<p>The <directive>CacheMinFileSize</directive> directive sets the

minimum size, in bytes, for a document to be considered for storage

in the cache.</p>

<example>

CacheMinFileSize 64

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheMaxFileSize</name>

<description>The maximum size (in bytes) of a document to be placed in the

cache</description>

<syntax>CacheMaxFileSize <var>bytes</var></syntax>

<default>CacheMaxFileSize 1000000</default>

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

</contextlist>

<usage>

<p>The <directive>CacheMaxFileSize</directive> directive sets the

maximum size, in bytes, for a document to be considered for storage in

the cache.</p>

<example>

CacheMaxFileSize 64000

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheReadSize</name>

<description>The minimum size (in bytes) of the document to read and be cached

before sending the data downstream</description>

<syntax>CacheReadSize <var>bytes</var></syntax>

<default>CacheReadSize 0</default>

<contextlist><context>server config</context>

<context>virtual host</context>

<context>directory</context>

<context>.htaccess</context>

</contextlist>

<usage>

<p>The <directive>CacheReadSize</directive> 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>

<example>

CacheReadSize 102400

</example>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>CacheReadTime</name>

<description>The minimum time (in milliseconds) that should elapse while reading

before data is sent downstream</description>

<syntax>CacheReadTime <var>milliseconds</var></syntax>

<default>CacheReadTime 0</default>

<contextlist><context>server config</context>

<context>virtual host</context>

<context>directory</context>

<context>.htaccess</context>

</contextlist>

<usage>

<p>The <directive>CacheReadTime</directive> 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

<directive module="mod_disk_cache">CacheReadSize</directive> directive to

ensure that the server does not buffer excessively should data arrive faster

than expected.</p>

<example>

CacheReadTime 1000

</example>

</usage>

</directivesynopsis>

</modulesynopsis>