2.4.x/docs/manual/mod/mod_buffer.xml

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

<name>mod_buffer</name>
<description>Support for request buffering</description>
<status>Extension</status>
<sourcefile>mod_buffer.c</sourcefile>
<identifier>buffer_module</identifier>
<compatibility>Available in Apache 2.3 and later</compatibility>

<summary>
    <p>This module provides the ability to buffer the input and output
    filter stacks.</p>

    <p>Under certain circumstances, content generators might create
    content in small chunks. In order to promote memory reuse, in
    memory chunks are always 8k in size, regardless of the size of the
    chunk itself. When many small chunks are generated by a request,
    this can create a large memory footprint while the request is
    being processed, and an unnecessarily large amount of data on the
    wire. The addition of a buffer collapses the response into the
    fewest chunks possible.</p>

    <p>When httpd is used in front of an expensive content generator,
    buffering the response may allow the backend to complete
    processing and release resources sooner, depending on how the
    backend is designed.</p>

    <p>The buffer filter may be added to either the input or the
    output filter stacks, as appropriate, using the
    <directive module="core">SetInputFilter</directive>,
    <directive module="core">SetOutputFilter</directive>,
    <directive module="mod_mime">AddOutputFilter</directive> or
    <directive module="mod_filter">AddOutputFilterByType</directive> directives.</p>

      <example><title>Using buffer with mod_include</title>
      <highlight language="config">
        AddOutputFilterByType INCLUDES;BUFFER text/html
        </highlight>
      </example>

    <note type="warning">The buffer filters read the request/response into
        RAM and then repack the request/response into the fewest memory
        buckets possible, at the cost of CPU time. When the request/response
        is already efficiently packed, buffering the request/response could
        cause the request/response to be slower than not using a buffer at
        all. These filters should be used with care, and only where
        necessary.</note>

</summary>
<seealso><a href="../filter.html">Filters</a></seealso>

<directivesynopsis>
<name>BufferSize</name>
<description>Maximum size in bytes to buffer by the buffer filter</description>
<syntax>BufferSize integer</syntax>
<default>BufferSize 131072</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
<context>.htaccess</context>
</contextlist>

<usage>
    <p>The <directive module="mod_buffer">BufferSize</directive>
    directive specifies the amount of data in bytes that will be
    buffered before being read from or written to each request.
    The default is 128 kilobytes.</p>
</usage>
</directivesynopsis>

</modulesynopsis>