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| <modulesynopsis metafile="mod_deflate.xml.meta"> |
| |
| <name>mod_deflate</name> |
| <description>Compress content before it is delivered to the |
| client</description> |
| <status>Extension</status> |
| <sourcefile>mod_deflate.c</sourcefile> |
| <identifier>deflate_module</identifier> |
| |
| <summary> |
| <p>The <module>mod_deflate</module> module provides |
| the <code>DEFLATE</code> output filter that allows output from |
| your server to be compressed 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> |
| <p>This is a simple sample configuration for the impatient.</p> |
| |
| <example><title>Compress only a few types</title> |
| AddOutputFilterByType DEFLATE text/html text/plain text/xml |
| </example> |
| |
| <p>The following configuration, while resulting in more compressed content, |
| is also much more complicated. Do not use this unless you fully understand |
| all the configuration details.</p> |
| |
| <example><title>Compress everything except images</title> |
| <Location /><br /> |
| <indent> |
| # Insert filter<br /> |
| SetOutputFilter DEFLATE<br /> |
| <br /> |
| # Netscape 4.x has some problems...<br /> |
| BrowserMatch ^Mozilla/4 gzip-only-text/html<br /> |
| <br /> |
| # Netscape 4.06-4.08 have some more problems<br /> |
| BrowserMatch ^Mozilla/4\.0[678] no-gzip<br /> |
| <br /> |
| # MSIE masquerades as Netscape, but it is fine<br /> |
| # BrowserMatch \bMSIE !no-gzip !gzip-only-text/html<br /> |
| <br /> |
| # NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48<br /> |
| # the above regex won't work. You can use the following<br /> |
| # workaround to get the desired effect:<br /> |
| BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html<br /> |
| <br /> |
| # Don't compress images<br /> |
| SetEnvIfNoCase Request_URI \<br /> |
| <indent> |
| \.(?:gif|jpe?g|png)$ no-gzip dont-vary<br /> |
| </indent> |
| <br /> |
| # Make sure proxies don't deliver the wrong content<br /> |
| Header append Vary User-Agent env=!dont-vary<br /> |
| </indent> |
| </Location> |
| </example> |
| |
| </section> |
| |
| <section id="enable"><title>Enabling Compression</title> |
| |
| <section id="output"><title>Output Compression</title> |
| <p>Compression is implemented by the <code>DEFLATE</code> |
| <a href="../filter.html">filter</a>. The following directive |
| will enable compression for documents in the container where it |
| is placed:</p> |
| |
| <example> |
| SetOutputFilter DEFLATE |
| </example> |
| |
| <p>Some popular browsers cannot handle compression of all content |
| so you may want to set the <code>gzip-only-text/html</code> note to |
| <code>1</code> to only allow html files to be compressed (see |
| below). If you set this to <em>anything but <code>1</code></em> it |
| will be ignored.</p> |
| |
| <p>If you want to restrict the compression to particular MIME types |
| in general, you may use the <directive module="core" |
| >AddOutputFilterByType</directive> directive. Here is an example of |
| enabling compression only for the html files of the Apache |
| documentation:</p> |
| |
| <example> |
| <Directory "/your-server-root/manual"><br /> |
| <indent> |
| AddOutputFilterByType DEFLATE text/html<br /> |
| </indent> |
| </Directory> |
| </example> |
| |
| <p>For browsers that have problems even with compression of all file |
| types, use the <directive module="mod_setenvif" |
| >BrowserMatch</directive> directive to set the <code>no-gzip</code> |
| note for that particular browser so that no compression will be |
| performed. You may combine <code>no-gzip</code> with <code |
| >gzip-only-text/html</code> to get the best results. In that case |
| the former overrides the latter. Take a look at the following |
| excerpt from the <a href="#recommended">configuration example</a> |
| defined in the section above:</p> |
| |
| <example> |
| BrowserMatch ^Mozilla/4 gzip-only-text/html<br /> |
| BrowserMatch ^Mozilla/4\.0[678] no-gzip<br /> |
| BrowserMatch \bMSIE !no-gzip !gzip-only-text/html |
| </example> |
| |
| <p>At first we probe for a <code>User-Agent</code> string that |
| indicates a Netscape Navigator version of 4.x. These versions |
| cannot handle compression of types other than |
| <code>text/html</code>. The versions 4.06, 4.07 and 4.08 also |
| have problems with decompressing html files. Thus, we completely |
| turn off the deflate filter for them.</p> |
| |
| <p>The third <directive module="mod_setenvif">BrowserMatch</directive> |
| directive fixes the guessed identity of the user agent, because |
| the Microsoft Internet Explorer identifies itself also as "Mozilla/4" |
| but is actually able to handle requested compression. Therefore we |
| match against the additional string "MSIE" (<code>\b</code> means |
| "word boundary") in the <code>User-Agent</code> Header and turn off |
| the restrictions defined before.</p> |
| |
| <note><title>Note</title> |
| The <code>DEFLATE</code> filter is always inserted after RESOURCE |
| filters like PHP or SSI. It never touches internal subrequests. |
| </note> |
| <note><title>Note</title> |
| There is a environment variable <code>force-gzip</code>, |
| set via <directive module="core">SetEnv</directive>, which |
| will ignore the accept-encoding setting of your browser and will |
| send compressed output. |
| </note> |
| |
| </section> |
| <section id="inflate"><title>Output Decompression</title> |
| <p>The <module>mod_deflate</module> module also provides a filter for |
| inflating/uncompressing a gzip compressed response body. In order to activate |
| this feature you have to insert the <code>INFLATE</code> filter into |
| the outputfilter chain using <directive module="core" |
| >SetOutputFilter</directive> or <directive module="mod_mime" |
| >AddOutputFilter</directive>, for example:</p> |
| |
| <example> |
| <Location /dav-area><br /> |
| <indent> |
| ProxyPass http://example.com/<br /> |
| SetOutputFilter INFLATE<br /> |
| </indent> |
| </Location> |
| </example> |
| |
| <p>This Example will uncompress gzip'ed output from example.com, so other |
| filters can do further processing with it. |
| </p> |
| |
| </section> |
| <section id="input"><title>Input Decompression</title> |
| <p>The <module>mod_deflate</module> module also provides a filter for |
| decompressing a gzip compressed request body . In order to activate |
| this feature you have to insert the <code>DEFLATE</code> filter into |
| the input filter chain using <directive module="core" |
| >SetInputFilter</directive> or <directive module="mod_mime" |
| >AddInputFilter</directive>, for example:</p> |
| |
| <example> |
| <Location /dav-area><br /> |
| <indent> |
| SetInputFilter DEFLATE<br /> |
| </indent> |
| </Location> |
| </example> |
| |
| <p>Now if a request contains a <code>Content-Encoding: |
| gzip</code> header, the body will be automatically decompressed. |
| Few browsers have the ability to gzip 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_deflate</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> |
| |
| <example> |
| Header append Vary User-Agent |
| </example> |
| |
| <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> |
| Header set Vary * |
| </example> |
| </section> |
| |
| <directivesynopsis> |
| <name>DeflateFilterNote</name> |
| <description>Places the compression ratio in a note for logging</description> |
| <syntax>DeflateFilterNote [<var>type</var>] <var>notename</var></syntax> |
| <contextlist><context>server config</context><context>virtual host</context> |
| </contextlist> |
| <compatibility><var>type</var> is available since Apache 2.0.45</compatibility> |
| |
| <usage> |
| <p>The <directive>DeflateFilterNote</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> |
| DeflateFilterNote ratio<br /> |
| <br /> |
| LogFormat '"%r" %b (%{ratio}n) "%{User-agent}i"' deflate<br /> |
| CustomLog logs/deflate_log deflate |
| </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 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> |
| DeflateFilterNote Input instream<br /> |
| DeflateFilterNote Output outstream<br /> |
| DeflateFilterNote Ratio ratio<br /> |
| <br /> |
| LogFormat '"%r" %{outstream}n/%{instream}n (%{ratio}n%%)' deflate<br /> |
| CustomLog logs/deflate_log deflate |
| </example> |
| </usage> |
| <seealso><module>mod_log_config</module></seealso> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>DeflateBufferSize</name> |
| <description>Fragment size to be compressed at one time by zlib</description> |
| <syntax>DeflateBufferSize <var>value</var></syntax> |
| <default>DeflateBufferSize 8096</default> |
| <contextlist><context>server config</context><context>virtual host</context> |
| </contextlist> |
| |
| <usage> |
| <p>The <directive>DeflateBufferSize</directive> directive specifies |
| the size in bytes of the fragments that zlib should compress at one |
| time.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>DeflateWindowSize</name> |
| <description>Zlib compression window size</description> |
| <syntax>DeflateWindowSize <var>value</var></syntax> |
| <default>DeflateWindowSize 15</default> |
| <contextlist><context>server config</context><context>virtual host</context> |
| </contextlist> |
| |
| <usage> |
| <p>The <directive>DeflateWindowSize</directive> directive specifies the |
| zlib compression window size (a value between 1 and 15). Generally, the |
| higher the window size, the higher can the compression ratio be expected.</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| |
| <name>DeflateMemLevel</name> |
| <description>How much memory should be used by zlib for compression</description> |
| <syntax>DeflateMemLevel <var>value</var></syntax> |
| <default>DeflateMemLevel 9</default> |
| <contextlist><context>server config</context><context>virtual host</context> |
| </contextlist> |
| |
| <usage> |
| <p>The <directive>DeflateMemLevel</directive> directive specifies |
| how much memory should be used by zlib for compression |
| (a value between 1 and 9).</p> |
| </usage> |
| </directivesynopsis> |
| |
| <directivesynopsis> |
| <name>DeflateCompressionLevel</name> |
| <description>How much compression do we apply to the output</description> |
| <syntax>DeflateCompressionLevel <var>value</var></syntax> |
| <default>Zlib's default</default> |
| <contextlist><context>server config</context><context>virtual host</context> |
| </contextlist> |
| <compatibility>This directive is available since Apache 2.0.45</compatibility> |
| |
| <usage> |
| <p>The <directive>DeflateCompressionLevel</directive> directive specifies |
| what level of compression should be used, the higher the value, |
| the better the compression, but the more CPU time is required to |
| achieve this.</p> |
| <p>The value must between 1 (less compression) and 9 (more compression).</p> |
| </usage> |
| </directivesynopsis> |
| |
| |
| </modulesynopsis> |
| |
