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<?xml version="1.0"?>
<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>
<!-- $LastChangedRevision$ -->
<!--
Copyright 2002-2005 The Apache Software Foundation or its licensors, as
applicable.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
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<modulesynopsis metafile="mod_mem_cache.xml.meta">
<name>mod_mem_cache</name>
<description>Content cache keyed to URIs</description>
<status>Extension</status>
<sourcefile>mod_mem_cache.c</sourcefile>
<identifier>mem_cache_module</identifier>
<summary>
<p>This module <em>requires</em> the service of <module
>mod_cache</module>. It acts as a support module for <module
>mod_cache</module> and provides a 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>).</p>
<p>Content is stored in and retrieved from the cache using URI based
keys. Content with access protection is not cached.</p>
</summary>
<seealso><module>mod_cache</module></seealso>
<seealso><module>mod_disk_cache</module></seealso>
<directivesynopsis>
<name>MCacheSize</name>
<description>The maximum amount of memory used by the cache in
KBytes</description>
<syntax>MCacheSize <var>KBytes</var></syntax>
<default>MCacheSize 100</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>The <directive>MCacheSize</directive> directive sets the maximum
amount of memory to be used by the cache, in KBytes (1024-byte units).
If a new object needs to be inserted in the cache and the size of the
object is greater than the remaining memory, objects will be removed
until the new object can be cached. The object to be removed is
selected using the algorithm specified by <directive
module="mod_mem_cache">MCacheRemovalAlgorithm</directive>.</p>
<example><title>Example</title>
MCacheSize 700000
</example>
<note><title>Note</title>
<p>The <directive>MCacheSize</directive> value must be greater than
the value specified by the <directive module="mod_mem_cache"
>MCacheMaxObjectSize</directive> directive.</p>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>MCacheMaxObjectCount</name>
<description>The maximum number of objects allowed to be placed in the
cache</description>
<syntax>MCacheMaxObjectCount <var>value</var></syntax>
<default>MCacheMaxObjectCount 1009</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>The <directive>MCacheMaxObjectCount</directive> directive sets the
maximum number of objects to be cached. The value is used to create the
open hash table. If a new object needs to be inserted in the cache and
the maximum number of objects has been reached, an object will be
removed to allow the new object to be cached. The object to be removed
is selected using the algorithm specified by <directive
module="mod_mem_cache">MCacheRemovalAlgorithm</directive>.</p>
<example><title>Example</title>
MCacheMaxObjectCount 13001
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>MCacheMinObjectSize</name>
<description>The minimum size (in bytes) of a document to be allowed in the
cache</description>
<syntax>MCacheMinObjectSize <var>bytes</var></syntax>
<default>MCacheMinObjectSize 0</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>The <directive>MCacheMinObjectSize</directive> directive sets the
minimum size in bytes of a document for it to be considered
cacheable.</p>
<example><title>Example</title>
MCacheMinObjectSize 10000
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>MCacheMaxObjectSize</name>
<description>The maximum size (in bytes) of a document allowed in the
cache</description>
<syntax>MCacheMaxObjectSize <var>bytes</var></syntax>
<default>MCacheMaxObjectSize 10000</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>The <directive>MCacheMaxObjectSize</directive> directive sets the
maximum allowable size, in bytes, of a document for it to be considered
cacheable.</p>
<example><title>Example</title>
MCacheMaxObjectSize 6400000
</example>
<note><title>Note</title>
<p>The value of <directive>MCacheMaxObjectSize</directive> must be
greater than the value specified by the <directive
module="mod_mem_cache">MCacheMinObjectSize</directive> directive.</p>
</note>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>MCacheRemovalAlgorithm</name>
<description>The algorithm used to select documents for removal from the
cache</description>
<syntax>MCacheRemovalAlgorithm LRU|GDSF</syntax>
<default>MCacheRemovalAlgorithm GDSF</default>
<contextlist><context>server config</context></contextlist>
<usage>
<p>The <directive>MCacheRemovalAlgorithm</directive> directive specifies
the algorithm used to select documents for removal from the cache.
Two choices are available:</p>
<dl>
<dt><code>LRU</code> (Least Recently Used)</dt>
<dd><code>LRU</code> removes the documents that have not been accessed
for the longest time.</dd>
<dt><code>GDSF</code> (GreadyDual-Size)</dt>
<dd><code>GDSF</code> assigns a priority to cached documents based
on the cost of a cache miss and the size of the document. Documents
with the lowest priority are removed first.</dd>
</dl>
<example><title>Example</title>
MCacheRemovalAlgorithm GDSF<br />
MCacheRemovalAlgorithm LRU
</example>
</usage>
</directivesynopsis>
<directivesynopsis>
<name>MCacheMaxStreamingBuffer</name>
<description>Maximum amount of a streamed response to buffer in memory
before declaring the response uncacheable</description>
<syntax>MCacheMaxStreamingBuffer <var>size_in_bytes</var></syntax>
<default>MCacheMaxStreamingBuffer the smaller of 100000 or MCacheMaxObjectSize</default>
<contextlist><context>server config</context>
</contextlist>
<usage>
<p>The <directive>MCacheMaxStreamingBuffer</directive> directive
specifies the maximum number of bytes of a streamed response to
buffer before deciding that the response is too big to cache.
A streamed response is one in which the entire content is not
immediately available and in which the <code>Content-Length</code>
may not be known. Sources of streaming responses include proxied
responses and the output of CGI scripts. 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.
The <directive>MCacheMaxStreamingBuffer</directive> directive allows
buffering of streamed responses that don't contain a
<code>Content-Length</code> up to the specified maximum amount of
space. If the maximum buffer space is reached, the buffered
content is discarded and the attempt to cache is abandoned.</p>
<note><title>Note:</title>
<p>Using a nonzero value for <directive>MCacheMaxStreamingBuffer</directive>
will not delay the transmission of the response to the client.
As soon as <module>mod_mem_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 />
MCacheMaxStreamingBuffer 65536
</example>
</usage>
</directivesynopsis>
</modulesynopsis>
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