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within the mod_cache provider interface to support an "in" brigade and an "out" brigade instead of just a single input brigade. This gives a cache provider the option to consume only part of the brigade passed to it, rather than the whole brigade as was required before. This fixes an out of memory and a request timeout condition that would occur when the original document was a large file. Update the mod_disk_cache provider implementation to take into account the new API. Introduce CacheReadSize and CacheReadTime directives to mod_disk_cache to control the amount of data to attempt to cache before sending the data on to the client in the "out" brigade. git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@996395 13f79535-47bb-0310-9956-ffa450edef68
243 lines
8.9 KiB
XML
243 lines
8.9 KiB
XML
<?xml version="1.0"?>
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<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
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<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
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<!-- $LastChangedRevision$ -->
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<!--
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<modulesynopsis metafile="mod_disk_cache.xml.meta">
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<name>mod_disk_cache</name>
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<description>Content cache storage manager keyed to URIs</description>
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<status>Extension</status>
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<sourcefile>mod_disk_cache.c</sourcefile>
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<identifier>disk_cache_module</identifier>
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<summary>
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<p><module>mod_disk_cache</module> implements a disk based storage
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manager. It is primarily of use in conjunction with
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<module>mod_cache</module>.</p>
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<p>Content is stored in and retrieved from the cache using URI based
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keys. Content with access protection is not cached.</p>
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<p><program>htcacheclean</program> can be used to maintain the cache
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size at a maximum level.</p>
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<note><title>Note:</title>
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<p><module>mod_disk_cache</module> requires the services of
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<module>mod_cache</module>.</p>
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</note>
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<note><title>Note:</title>
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<p><module>mod_disk_cache</module> uses the sendfile feature to
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serve files from the cache when supported by the platform, and
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when enabled with <directive module="core">EnableSendfile</directive>.
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However, per-directory and .htaccess configuration of
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<directive module="core">EnableSendfile</directive> are ignored by
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<module>mod_disk_cache</module> as the corresponding settings are not
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available to the module when a request is being served from the
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cache.</p>
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</note>
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</summary>
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<directivesynopsis>
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<name>CacheRoot</name>
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<description>The directory root under which cache files are
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stored</description>
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<syntax>CacheRoot <var>directory</var></syntax>
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<contextlist><context>server config</context><context>virtual host</context>
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</contextlist>
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<usage>
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<p>The <directive>CacheRoot</directive> directive defines the name of
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the directory on the disk to contain cache files. If the <module
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>mod_disk_cache</module> module has been loaded or compiled in to the
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Apache server, this directive <em>must</em> be defined. Failing to
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provide a value for <directive>CacheRoot</directive> will result in
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a configuration file processing error. The <directive
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module="mod_disk_cache">CacheDirLevels</directive> and <directive
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module="mod_disk_cache">CacheDirLength</directive> directives define
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the structure of the directories under the specified root directory.</p>
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<example>
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CacheRoot c:/cacheroot
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</example>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>CacheDirLevels</name>
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<description>The number of levels of subdirectories in the
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cache.</description>
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<syntax>CacheDirLevels <var>levels</var></syntax>
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<default>CacheDirLevels 2</default>
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<contextlist><context>server config</context><context>virtual host</context>
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</contextlist>
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<usage>
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<p>The <directive>CacheDirLevels</directive> directive sets the number
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of subdirectory levels in the cache. Cached data will be saved this
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many directory levels below the <directive module="mod_disk_cache"
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>CacheRoot</directive> directory.</p>
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<p>A high value for <directive>CacheDirLevels</directive> combined
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with a low value for <directive>CacheDirLength</directive> will result in
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a relatively deep hierarchy, with a small number of subdirectories at each
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level.</p>
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<note>
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<p>The result of <directive>CacheDirLevels</directive>*
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<directive module="mod_disk_cache">CacheDirLength</directive> must
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not be higher than 20.</p>
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</note>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>CacheDirLength</name>
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<description>The number of characters in subdirectory names</description>
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<syntax>CacheDirLength <var>length</var></syntax>
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<default>CacheDirLength 2</default>
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<contextlist><context>server config</context><context>virtual host</context>
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</contextlist>
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<usage>
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<p>The <directive>CacheDirLength</directive> directive sets the number
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of characters for each subdirectory name in the cache hierarchy. It can
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be used in conjunction with <directive>CacheDirLevels</directive> to
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determine the approximate structure of your cache hierarchy.</p>
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<p>A high value for <directive>CacheDirLength</directive> combined
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with a low value for <directive>CacheDirLevels</directive> will result in
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a relatively flat hierarchy, with a large number of subdirectories at each
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level.</p>
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<note>
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<p>The result of <directive module="mod_disk_cache"
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>CacheDirLevels</directive>* <directive>CacheDirLength</directive>
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must not be higher than 20.</p>
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</note>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>CacheMinFileSize</name>
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<description>The minimum size (in bytes) of a document to be placed in the
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cache</description>
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<syntax>CacheMinFileSize <var>bytes</var></syntax>
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<default>CacheMinFileSize 1</default>
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<contextlist><context>server config</context><context>virtual host</context>
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</contextlist>
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<usage>
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<p>The <directive>CacheMinFileSize</directive> directive sets the
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minimum size, in bytes, for a document to be considered for storage
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in the cache.</p>
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<example>
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CacheMinFileSize 64
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</example>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>CacheMaxFileSize</name>
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<description>The maximum size (in bytes) of a document to be placed in the
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cache</description>
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<syntax>CacheMaxFileSize <var>bytes</var></syntax>
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<default>CacheMaxFileSize 1000000</default>
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<contextlist><context>server config</context><context>virtual host</context>
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</contextlist>
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<usage>
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<p>The <directive>CacheMaxFileSize</directive> directive sets the
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maximum size, in bytes, for a document to be considered for storage in
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the cache.</p>
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<example>
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CacheMaxFileSize 64000
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</example>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>CacheReadSize</name>
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<description>The minimum size (in bytes) of the document to read and be cached
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before sending the data downstream</description>
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<syntax>CacheReadSize <var>bytes</var></syntax>
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<default>CacheReadSize 0</default>
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<contextlist><context>server config</context>
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<context>virtual host</context>
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<context>directory</context>
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<context>.htaccess</context>
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</contextlist>
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<usage>
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<p>The <directive>CacheReadSize</directive> directive sets the
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minimum amount of data, in bytes, to be read from the backend before the
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data is sent to the client. The default of zero causes all data read of
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any size to be passed downstream to the client immediately as it arrives.
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Setting this to a higher value causes the disk cache to buffer at least
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this amount before sending the result to the client. This can improve
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performance when caching content from a reverse proxy.</p>
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<p>This directive only takes effect when the data is being saved to the
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cache, as opposed to data being served from the cache.</p>
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<example>
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CacheReadSize 102400
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</example>
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</usage>
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</directivesynopsis>
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<directivesynopsis>
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<name>CacheReadTime</name>
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<description>The minimum time (in milliseconds) that should elapse while reading
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before data is sent downstream</description>
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<syntax>CacheReadTime <var>milliseconds</var></syntax>
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<default>CacheReadTime 0</default>
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<contextlist><context>server config</context>
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<context>virtual host</context>
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<context>directory</context>
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<context>.htaccess</context>
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</contextlist>
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<usage>
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<p>The <directive>CacheReadTime</directive> directive sets the minimum amount
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of elapsed time that should pass before making an attempt to send data
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downstream to the client. During the time period, data will be buffered
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before sending the result to the client. This can improve performance when
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caching content from a reverse proxy.</p>
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<p>The default of zero disables this option.</p>
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<p>This directive only takes effect when the data is being saved to the
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cache, as opposed to data being served from the cache. It is recommended
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that this option be used alongside the
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<directive module="mod_disk_cache">CacheReadSize</directive> directive to
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ensure that the server does not buffer excessively should data arrive faster
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than expected.</p>
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<example>
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CacheReadTime 1000
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</example>
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</usage>
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</directivesynopsis>
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</modulesynopsis>
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