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Posted to cvs@httpd.apache.org by ji...@apache.org on 2017/01/16 19:51:31 UTC
svn commit: r1779091 - /httpd/httpd/trunk/docs/manual/mod/mod_brotli.xml
Author: jim
Date: Mon Jan 16 19:51:31 2017
New Revision: 1779091
URL: http://svn.apache.org/viewvc?rev=1779091&view=rev
Log:
1st draft
Added:
httpd/httpd/trunk/docs/manual/mod/mod_brotli.xml
Added: httpd/httpd/trunk/docs/manual/mod/mod_brotli.xml
URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/docs/manual/mod/mod_brotli.xml?rev=1779091&view=auto
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--- httpd/httpd/trunk/docs/manual/mod/mod_brotli.xml (added)
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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: 1726578 $ -->
+
+<!--
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You 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.
+-->
+
+<modulesynopsis metafile="mod_brotli.xml.meta">
+
+<name>mod_brotli</name>
+<description>Compress content via Brotli before it is delivered to the
+client</description>
+<status>Extension</status>
+<sourcefile>mod_brotli.c</sourcefile>
+<identifier>brotli_module</identifier>
+
+<summary>
+ <p>The <module>mod_brotli</module> module provides
+ the <code>BROTLI_COMPRESS</code> output filter that allows output from
+ your server to be compressed using the brotli compression format before being sent to the client over
+ the network.</p>
+</summary>
+<seealso><a href="../filter.html">Filters</a></seealso>
+
+<section id="recommended"><title>Sample Configurations</title>
+ <note type="warning"><title>Compression and TLS</title>
+ <p>Some web applications are vulnerable to an information disclosure
+ attack when a TLS connection carries deflate compressed data. For more
+ information, review the details of the "BREACH" family of attacks.</p>
+ </note>
+ <p>This is a simple configuration that compresses common text-based content types.</p>
+
+ <example><title>Compress only a few types</title>
+ <highlight language="config">
+ AddOutputFilterByType BROTLI_COMPRESS text/html text/plain text/xml text/css text/javascript application/javascript
+ </highlight>
+ </example>
+
+</section>
+
+<section id="enable"><title>Enabling Compression</title>
+ <note type="warning"><title>Compression and TLS</title>
+ <p>Some web applications are vulnerable to an information disclosure
+ attack when a TLS connection carries deflate compressed data. For more
+ information, review the details of the "BREACH" family of attacks.</p>
+ </note>
+
+ <section id="output"><title>Output Compression</title>
+ <p>Compression is implemented by the <code>BROTLI_COMPRESS</code>
+ <a href="../filter.html">filter</a>. The following directive
+ will enable compression for documents in the container where it
+ is placed:</p>
+
+ <highlight language="config">
+SetOutputFilter BROTLI_COMPRESS
+SetEnvIfNoCase Request_URI \.(?:gif|jpe?g|png)$ no-brotli
+ </highlight>
+
+ <p>If you want to restrict the compression to particular MIME types
+ in general, you may use the <directive module="mod_filter"
+ >AddOutputFilterByType</directive> directive. Here is an example of
+ enabling compression only for the html files of the Apache
+ documentation:</p>
+
+ <highlight language="config">
+<Directory "/your-server-root/manual">
+ AddOutputFilterByType BROTLI_COMPRESS text/html
+</Directory>
+ </highlight>
+
+ <note><title>Note</title>
+ The <code>BROTLI_COMPRESS</code> filter is always inserted after RESOURCE
+ filters like PHP or SSI. It never touches internal subrequests.
+ </note>
+ <note><title>Note</title>
+ There is an environment variable <code>no-brotli</code>,
+ set via <directive module="mod_env">SetEnv</directive>, which
+ will ignore the accept-encoding setting of your browser and will
+ send compressed output.
+ </note>
+
+ </section>
+
+ <section id="input"><title>Input Decompression</title>
+ <p>The <module>mod_brotli</module> module also provides a filter for
+ decompressing a brotli compressed request body . In order to activate
+ this feature you have to insert the <code>BROTLI_COMPRESS</code> filter into
+ the input filter chain using <directive module="core"
+ >SetInputFilter</directive> or <directive module="mod_mime"
+ >AddInputFilter</directive>, for example:</p>
+
+ <highlight language="config">
+<Location "/dav-area">
+ SetInputFilter BROTLI_COMPRESS
+</Location>
+ </highlight>
+
+ <p>Now if a request contains a <code>Content-Encoding:
+ brotli</code> header, the body will be automatically decompressed.
+ Few browsers have the ability to brotli request bodies. However,
+ some special applications actually do support request
+ compression, for instance some <a
+ href="http://www.webdav.org">WebDAV</a> clients.</p>
+
+ <note type="warning"><title>Note on Content-Length</title>
+ <p>If you evaluate the request body yourself, <em>don't trust
+ the <code>Content-Length</code> header!</em>
+ The Content-Length header reflects the length of the
+ incoming data from the client and <em>not</em> the byte count of
+ the decompressed data stream.</p>
+ </note>
+ </section>
+</section>
+
+<section id="proxies"><title>Dealing with proxy servers</title>
+
+ <p>The <module>mod_brotli</module> module sends a <code>Vary:
+ Accept-Encoding</code> HTTP response header to alert proxies that
+ a cached response should be sent only to clients that send the
+ appropriate <code>Accept-Encoding</code> request header. This
+ prevents compressed content from being sent to a client that will
+ not understand it.</p>
+
+ <p>If you use some special exclusions dependent
+ on, for example, the <code>User-Agent</code> header, you must
+ manually configure an addition to the <code>Vary</code> header
+ to alert proxies of the additional restrictions. For example,
+ in a typical configuration where the addition of the <code>DEFLATE</code>
+ filter depends on the <code>User-Agent</code>, you should add:</p>
+
+ <highlight language="config">
+ Header append Vary User-Agent
+ </highlight>
+
+ <p>If your decision about compression depends on other information
+ than request headers (<em>e.g.</em> HTTP version), you have to set the
+ <code>Vary</code> header to the value <code>*</code>. This prevents
+ compliant proxies from caching entirely.</p>
+
+ <example><title>Example</title>
+ <highlight language="config">
+ Header set Vary *
+ </highlight>
+ </example>
+</section>
+
+<section id="precompressed"><title>Serving pre-compressed
+content</title>
+
+ <p>Since <module>mod_brotli</module> re-compresses content each
+ time a request is made, some performance benefit can be derived by
+ pre-compressing the content and telling mod_brotli to serve them
+ without re-compressing them. This may be accomplished using a
+ configuration like the following:</p>
+
+ <highlight language="config">
+<IfModule mod_headers.c>
+ # Serve brotli compressed CSS files if they exist
+ # and the client accepts brotli.
+ RewriteCond "%{HTTP:Accept-encoding}" "brotli"
+ RewriteCond "%{REQUEST_FILENAME}\.br" "-s"
+ RewriteRule "^(.*)\.css" "$1\.css\.br" [QSA]
+
+ # Serve brotli compressed JS files if they exist
+ # and the client accepts brotli.
+ RewriteCond "%{HTTP:Accept-encoding}" "brotli"
+ RewriteCond "%{REQUEST_FILENAME}\.br" "-s"
+ RewriteRule "^(.*)\.js" "$1\.js\.br" [QSA]
+
+
+ # Serve correct content types, and prevent mod_brotli double brotli.
+ RewriteRule "\.css\.gz$" "-" [T=text/css,E=no-brotli:1]
+ RewriteRule "\.js\.gz$" "-" [T=text/javascript,E=no-brotli:1]
+
+
+ <FilesMatch "(\.js\.gz|\.css\.gz)$">
+ # Serve correct encoding type.
+ Header append Content-Encoding brotli
+
+ # Force proxies to cache brotli &
+ # non-brotli css/js files separately.
+ Header append Vary Accept-Encoding
+ </FilesMatch>
+</IfModule>
+ </highlight>
+
+</section>
+
+<directivesynopsis>
+<name>BrotliFilterNote</name>
+<description>Places the compression ratio in a note for logging</description>
+<syntax>BrotliFilterNote [<var>type</var>] <var>notename</var></syntax>
+<contextlist><context>server config</context><context>virtual host</context>
+</contextlist>
+
+<usage>
+ <p>The <directive>BrotliFilterNote</directive> directive
+ specifies that a note about compression ratios should be attached
+ to the request. The name of the note is the value specified for
+ the directive. You can use that note for statistical purposes by
+ adding the value to your <a href="../logs.html#accesslog"
+ >access log</a>.</p>
+
+ <example><title>Example</title>
+ <highlight language="config">
+ BrotliFilterNote ratio
+
+ LogFormat '"%r" %b (%{ratio}n) "%{User-agent}i"' brotli
+ CustomLog "logs/brotli_log" brotli
+ </highlight>
+ </example>
+
+ <p>If you want to extract more accurate values from your logs, you
+ can use the <var>type</var> argument to specify the type of data
+ left as a note for logging. <var>type</var> can be one of:</p>
+
+ <dl>
+ <dt><code>Input</code></dt>
+ <dd>Store the byte count of the filter's input stream in the note.</dd>
+
+ <dt><code>Output</code></dt>
+ <dd>Store the byte count of the filter's output stream in the note.</dd>
+
+ <dt><code>Ratio</code></dt>
+ <dd>Store the compression ratio (<code>output/input * 100</code>)
+ in the note. This is the default, if the <var>type</var> argument
+ is omitted.</dd>
+ </dl>
+
+ <p>Thus you may log it this way:</p>
+
+ <example><title>Accurate Logging</title>
+ <highlight language="config">
+BrotliFilterNote Input instream
+BrotliFilterNote Output outstream
+BrotliFilterNote Ratio ratio
+
+LogFormat '"%r" %{outstream}n/%{instream}n (%{ratio}n%%)' brotli
+CustomLog "logs/brotli_log" brotli
+</highlight>
+ </example>
+</usage>
+<seealso><module>mod_log_config</module></seealso>
+</directivesynopsis>
+
+<directivesynopsis>
+<name>BrotliCompressionQuality</name>
+<description>Compression quality</description>
+<syntax>BrotliCompressionQuality <var>value</var></syntax>
+<default>BrotliCompressionQuality 5</default>
+<contextlist><context>server config</context><context>virtual host</context>
+</contextlist>
+
+<usage>
+ <p>The <directive>BrotliCompressionQuality</directive> directive specifies
+ the compression quality performed (a value between 0 and 11). Higher
+ quality values result in better compression but also slower compression
+ as well.
+ </p>
+</usage>
+</directivesynopsis>
+
+<directivesynopsis>
+<name>BrotliCompressionWindow</name>
+<description>Brotli sliding compression window size</description>
+<syntax>BrotliCompressionWindow <var>value</var></syntax>
+<default>BrotliCompressionWindow 18</default>
+<contextlist><context>server config</context><context>virtual host</context>
+</contextlist>
+
+<usage>
+ <p>The <directive>BrotliCompressionWindow</directive> directive specifies the
+ brotli sliding compression window size (a value between 10 and 24). Generally, the
+ higher the window size, the higher can the compression ratio be expected
+ but requires more memory.</p>
+</usage>
+</directivesynopsis>
+
+<directivesynopsis>
+
+<name>BrotliCompressionMaxInputBlock</name>
+<description>Maximum input block size</description>
+<syntax>BrotliCompressionMaxInputBlock <var>value</var></syntax>
+<default>BrotliCompressionMaxInputBlock 0</default>
+<contextlist><context>server config</context><context>virtual host</context>
+</contextlist>
+
+<usage>
+ <p>The <directive>BrotliCompressionMaxInputBlock</directive> directive specifies
+ the maximum input block size between 16 and 24, with the caveat that
+ larger block sizes require more memory.</p>
+</usage>
+</directivesynopsis>
+
+<directivesynopsis>
+<name>BrotliAlterETag</name>
+<description>How the outgoing ETag header should be modified during compression</description>
+<syntax>BrotliAlterETag AddSuffix|NoChange|Remove</syntax>
+<default>BrotliAlterETag AddSuffix</default>
+<contextlist><context>server config</context><context>virtual host</context>
+</contextlist>
+
+<usage>
+ <p>The <directive>BrotliAlterETag</directive> directive specifies
+ how the ETag hader should be altered when a response is compressed.</p>
+ <dl>
+ <dt>AddSuffix</dt>
+ <dd><p>Append the compression method onto the end of the ETag, causing
+ compressed and uncompressed representations to have unique ETags.
+ This has been the default since 2.4.0, but prevents serving
+ "HTTP Not Modified" (304) responses to conditional requests for
+ compressed content.</p></dd>
+ <dt>NoChange</dt>
+ <dd><p>Don't change the ETag on a compressed response. This was the default
+ prior to 2.4.0, but does not satisfy the HTTP/1.1 property that all
+ representations of the same resource have unique ETags. </p></dd>
+ <dt>Remove</dt>
+ <dd><p>Remove the ETag header from compressed responses. This prevents
+ some conditional requests from being possible, but avoids the
+ shortcomings of the preceding options. </p></dd>
+ </dl>
+</usage>
+</directivesynopsis>
+
+</modulesynopsis>