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462 lines
18 KiB
XML
462 lines
18 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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Copyright 2002-2006 The Apache Software Foundation or its licensors, as
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applicable.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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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_cache.xml.meta">
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<name>mod_cache</name>
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<description>Content cache keyed to URIs.</description>
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<status>Extension</status>
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<sourcefile>mod_cache.c</sourcefile>
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<identifier>cache_module</identifier>
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<summary>
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<note type="warning">This module should be used with care and
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can be used to circumvent <directive
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module="mod_authz_host">Allow</directive> and <directive
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module="mod_authz_host">Deny</directive> directives. You
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should not enable caching for any content to which you wish
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to limit access by client host name, address or environment
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variable.</note>
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<p><module>mod_cache</module> implements an <a
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href="http://www.ietf.org/rfc/rfc2616.txt">RFC 2616</a> compliant HTTP
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content cache that can be used to cache either local or proxied content.
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<module>mod_cache</module> requires the services of one or more storage
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management modules. Two storage management modules are included in
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the base Apache distribution:</p>
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<dl>
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<dt><module>mod_disk_cache</module></dt>
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<dd>implements a disk based storage manager.</dd>
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<dt><module>mod_mem_cache</module></dt>
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<dd>implements a memory based storage manager.
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<module>mod_mem_cache</module> can be configured to operate in two
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modes: caching open file descriptors or caching objects in heap storage.
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<module>mod_mem_cache</module> can be used to cache locally generated content
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or to cache backend server content for <module>mod_proxy</module> when
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configured using <directive module="mod_proxy">ProxyPass</directive>
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(aka <dfn>reverse proxy</dfn>)</dd>
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</dl>
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<p>Content is stored in and retrieved from the cache using URI based keys. Content with
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access protection is not cached.</p>
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</summary>
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<section id="related"><title>Related Modules and Directives</title>
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<related>
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<modulelist>
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<module>mod_disk_cache</module>
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<module>mod_mem_cache</module>
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</modulelist>
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<directivelist>
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<directive module="mod_disk_cache">CacheRoot</directive>
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<directive module="mod_disk_cache">CacheDirLevels</directive>
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<directive module="mod_disk_cache">CacheDirLength</directive>
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<directive module="mod_disk_cache">CacheMinFileSize</directive>
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<directive module="mod_disk_cache">CacheMaxFileSize</directive>
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<directive module="mod_mem_cache">MCacheSize</directive>
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<directive module="mod_mem_cache">MCacheMaxObjectCount</directive>
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<directive module="mod_mem_cache">MCacheMinObjectSize</directive>
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<directive module="mod_mem_cache">MCacheMaxObjectSize</directive>
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<directive module="mod_mem_cache">MCacheRemovalAlgorithm</directive>
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<directive module="mod_mem_cache">MCacheMaxStreamingBuffer</directive>
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</directivelist>
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</related>
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</section>
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<section id="sampleconf"><title>Sample Configuration</title>
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<example><title>Sample httpd.conf</title>
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#<br />
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# Sample Cache Configuration<br />
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#<br />
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LoadModule cache_module modules/mod_cache.so<br />
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<br />
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<IfModule mod_cache.c><br />
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<indent>
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#LoadModule disk_cache_module modules/mod_disk_cache.so<br />
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# If you want to use mod_disk_cache instead of mod_mem_cache,<br />
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# uncomment the line above and comment out the LoadModule line below.<br />
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<IfModule mod_disk_cache.c><br />
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<indent>
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CacheRoot c:/cacheroot<br />
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CacheEnable disk /<br />
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CacheDirLevels 5<br />
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CacheDirLength 3<br />
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</indent>
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</IfModule> <br />
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<br />
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LoadModule mem_cache_module modules/mod_mem_cache.so<br />
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<IfModule mod_mem_cache.c><br />
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<indent>
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CacheEnable mem /<br />
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MCacheSize 4096<br />
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MCacheMaxObjectCount 100<br />
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MCacheMinObjectSize 1<br />
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MCacheMaxObjectSize 2048<br />
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</indent>
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</IfModule><br />
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<br />
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# When acting as a proxy, don't cache the list of security updates<br />
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CacheDisable http://security.update.server/update-list/<br />
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</indent>
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</IfModule>
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</example>
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</section>
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<directivesynopsis>
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<name>CacheEnable</name>
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<description>Enable caching of specified URLs using a specified storage
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manager</description>
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<syntax>CacheEnable <var>cache_type</var> <var>url-string</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>CacheEnable</directive> directive instructs
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<module>mod_cache</module> to cache urls at or below
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<var>url-string</var>. The cache storage manager is specified with the
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<var>cache_type</var> argument. <var>cache_type</var> <code> mem</code>
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instructs <module>mod_cache</module> to use the memory based storage
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manager implemented by <module>mod_mem_cache</module>.
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<var>cache_type</var> <code>disk</code> instructs
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<module>mod_cache</module> to use the disk based storage manager
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implemented by <module>mod_disk_cache</module>.
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<var>cache_type</var> <code>fd</code> instructs
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<module>mod_cache</module> to use the file descriptor cache implemented
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by <module>mod_mem_cache</module>.</p>
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<p>In the event that the URL space overlaps between different
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<directive>CacheEnable</directive> directives (as in the example below),
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each possible storage manager will be run until the first one that
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actually processes the request. The order in which the storage managers are
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run is determined by the order of the <directive>CacheEnable</directive>
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directives in the configuration file.</p>
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<example>
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CacheEnable mem /manual<br />
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CacheEnable fd /images<br />
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CacheEnable disk /<br />
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</example>
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<p>When acting as a forward proxy server, <var>url-string</var> can
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also be used to specify remote sites and proxy protocols which
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caching should be enabled for.</p>
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<example>
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# Cache proxied url's<br />
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CacheEnable disk /<br /><br />
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# Cache FTP-proxied url's<br />
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CacheEnable disk ftp://<br /><br />
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# Cache content from www.apache.org<br />
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CacheEnable disk http://www.apache.org/<br />
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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>CacheDisable</name>
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<description>Disable caching of specified URLs</description>
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<syntax>CacheDisable <var> url-string</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>CacheDisable</directive> directive instructs
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<module>mod_cache</module> to <em>not</em> cache urls at or below
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<var>url-string</var>.</p>
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<example><title>Example</title>
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CacheDisable /local_files
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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>CacheMaxExpire</name>
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<description>The maximum time in seconds to cache a document</description>
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<syntax>CacheMaxExpire <var>seconds</var></syntax>
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<default>CacheMaxExpire 86400 (one day)</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>CacheMaxExpire</directive> directive specifies the maximum number of
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seconds for which cachable HTTP documents will be retained without checking the origin
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server. Thus, documents will be out of date at most this number of seconds. This maximum
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value is enforced even if an expiry date was supplied with the document.</p>
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<example>
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CacheMaxExpire 604800
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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>CacheMinExpire</name>
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<description>The minimum time in seconds to cache a document</description>
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<syntax>CacheMinExpire <var>seconds</var></syntax>
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<default>CacheMinExpire 0</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>CacheMinExpire</directive> directive specifies the minimum number of
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seconds for which cachable HTTP documents will be retained without checking the origin
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server. This is only used if no valid expire time was supplied with the document.</p>
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<example>
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CacheMinExpire 3600
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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>CacheDefaultExpire</name>
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<description>The default duration to cache a document when no expiry date is specified.</description>
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<syntax>CacheDefaultExpire <var>seconds</var></syntax>
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<default>CacheDefaultExpire 3600 (one hour)</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>CacheDefaultExpire</directive> directive specifies a default time,
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in seconds, to cache a document if neither an expiry date nor last-modified date are provided
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with the document. The value specified with the <directive>CacheMaxExpire</directive>
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directive does <em>not</em> override this setting.</p>
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<example>
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CacheDefaultExpire 86400
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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>CacheIgnoreNoLastMod</name>
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<description>Ignore the fact that a response has no Last Modified
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header.</description>
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<syntax>CacheIgnoreNoLastMod On|Off</syntax>
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<default>CacheIgnoreNoLastMod Off</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>Ordinarily, documents without a last-modified date are not cached.
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Under some circumstances the last-modified date is removed (during
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<module>mod_include</module> processing for example) or not provided
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at all. The <directive>CacheIgnoreNoLastMod</directive> directive
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provides a way to specify that documents without last-modified dates
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should be considered for caching, even without a last-modified date.
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If neither a last-modified date nor an expiry date are provided with
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the document then the value specified by the
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<directive>CacheDefaultExpire</directive> directive will be used to
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generate an expiration date.</p>
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<example>
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CacheIgnoreNoLastMod On
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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>CacheIgnoreCacheControl</name>
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<description>Ignore request to not serve cached content to client</description>
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<syntax>CacheIgnoreCacheControl On|Off</syntax>
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<default>CacheIgnoreCacheControl Off</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>Ordinarily, requests containing a Cache-Control: no-cache or
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Pragma: no-cache header value will not be served from the cache. The
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<directive>CacheIgnoreCacheControl</directive> directive allows this
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behavior to be overridden. <directive>CacheIgnoreCacheControl</directive>
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On tells the server to attempt to serve the resource from the cache even
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if the request contains no-cache header values. Resources requiring
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authorization will <em>never</em> be cached.</p>
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<example>
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CacheIgnoreCacheControl On
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</example>
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<note type="warning"><title>Warning:</title>
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This directive will allow serving from the cache even if the client has
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requested that the document not be served from the cache. This might
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result in stale content being served.
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</note>
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</usage>
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<seealso><directive module="mod_cache">CacheStorePrivate</directive></seealso>
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<seealso><directive module="mod_cache">CacheStoreNoStore</directive></seealso>
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</directivesynopsis>
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<directivesynopsis>
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<name>CacheLastModifiedFactor</name>
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<description>The factor used to compute an expiry date based on the
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LastModified date.</description>
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<syntax>CacheLastModifiedFactor <var>float</var></syntax>
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<default>CacheLastModifiedFactor 0.1</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>In the event that a document does not provide an expiry date but does
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provide a last-modified date, an expiry date can be calculated based on
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the time since the document was last modified. The
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<directive>CacheLastModifiedFactor</directive> directive specifies a
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<var>factor</var> to be used in the generation of this expiry date
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according to the following formula:
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<code>expiry-period = time-since-last-modified-date * <var>factor</var>
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expiry-date = current-date + expiry-period</code>
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For example, if the document was last modified 10 hours ago, and
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<var>factor</var> is 0.1 then the expiry-period will be set to
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10*0.1 = 1 hour. If the current time was 3:00pm then the computed
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expiry-date would be 3:00pm + 1hour = 4:00pm.
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If the expiry-period would be longer than that set by
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<directive>CacheMaxExpire</directive>, then the latter takes
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precedence.</p>
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<example>
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CacheLastModifiedFactor 0.5
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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>CacheIgnoreHeaders</name>
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<description>Do not store the given HTTP header(s) in the cache.
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</description>
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<syntax>CacheIgnoreHeaders <var>header-string</var> [<var>header-string</var>] ...</syntax>
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<default>CacheIgnoreHeaders None</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>According to RFC 2616, hop-by-hop HTTP headers are not stored in
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the cache. The following HTTP headers are hop-by-hop headers and thus
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do not get stored in the cache in <em>any</em> case regardless of the
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setting of <directive>CacheIgnoreHeaders</directive>:</p>
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<ul>
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<li><code>Connection</code></li>
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<li><code>Keep-Alive</code></li>
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<li><code>Proxy-Authenticate</code></li>
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<li><code>Proxy-Authorization</code></li>
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<li><code>TE</code></li>
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<li><code>Trailers</code></li>
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<li><code>Transfer-Encoding</code></li>
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<li><code>Upgrade</code></li>
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</ul>
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<p><directive>CacheIgnoreHeaders</directive> specifies additional HTTP
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headers that should not to be stored in the cache. For example, it makes
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sense in some cases to prevent cookies from being stored in the cache.</p>
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<p><directive>CacheIgnoreHeaders</directive> takes a space separated list
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of HTTP headers that should not be stored in the cache. If only hop-by-hop
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headers not should be stored in the cache (the RFC 2616 compliant
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behaviour), <directive>CacheIgnoreHeaders</directive> can be set to
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<code>None</code>.</p>
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<example><title>Example 1</title>
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CacheIgnoreHeaders Set-Cookie
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</example>
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<example><title>Example 2</title>
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CacheIgnoreHeaders None
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</example>
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<note type="warning"><title>Warning:</title>
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If headers like <code>Expires</code> which are needed for proper cache
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management are not stored due to a
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<directive>CacheIgnoreHeaders</directive> setting, the behaviour of
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mod_cache is undefined.
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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>CacheStorePrivate</name>
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<description>Attempt to cache responses that the server has marked as private</description>
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<syntax>CacheStorePrivate On|Off</syntax>
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<default>CacheStorePrivate Off</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>Ordinarily, responses with Cache-Control: private header values will not
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be stored in the cache. The <directive>CacheStorePrivate</directive>
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directive allows this behavior to be overridden.
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<directive>CacheStorePrivate</directive> On
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tells the server to attempt to cache the resource even if it contains
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private header values. Resources requiring authorization will
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<em>never</em> be cached.</p>
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<example>
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CacheStorePrivate On
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</example>
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<note type="warning"><title>Warning:</title>
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This directive will allow caching even if the upstream server has
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requested that the resource not be cached. This directive is only
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ideal for a 'private' cache.
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</note>
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</usage>
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<seealso><directive module="mod_cache">CacheIgnoreCacheControl</directive></seealso>
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<seealso><directive module="mod_cache">CacheStoreNoStore</directive></seealso>
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</directivesynopsis>
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<directivesynopsis>
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<name>CacheStoreNoStore</name>
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<description>Attempt to cache requests or responses that have been marked as no-store.</description>
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<syntax>CacheStoreNoStore On|Off</syntax>
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<default>CacheStoreNoStore Off</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>Ordinarily, requests or responses with Cache-Control: no-store header
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values will not be stored in the cache. The
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<directive>CacheStoreNoCache</directive> directive allows this
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behavior to be overridden. <directive>CacheStoreNoCache</directive> On
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tells the server to attempt to cache the resource even if it contains
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no-store header values. Resources requiring authorization will
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<em>never</em> be cached.</p>
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<example>
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CacheStoreNoStore On
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</example>
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<note type="warning"><title>Warning:</title>
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As described in RFC 2616, the no-store directive is intended to
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"prevent the inadvertent release or retention of sensitive information
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(for example, on backup tapes)." Enabling this option could store
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sensitive information in the cache. You are hereby warned.
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</note>
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</usage>
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<seealso><directive module="mod_cache">CacheIgnoreCacheControl</directive></seealso>
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<seealso><directive module="mod_cache">CacheStorePrivate</directive></seealso>
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</directivesynopsis>
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</modulesynopsis>
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