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Revision 33 (zachera, 2010-05-29 01:40) → Revision 34/39 (zachera, 2010-05-29 01:41)

h1. Output Compression 

 *Module: mod_compress* 

 {{>toc}} 

 h2. Description 

 Output compression reduces the network load and can improve the overall 
 throughput of the webserver. All major http-clients support compression by 
 announcing it in the Accept-Encoding header. This is used to negotiate the  
 most suitable compression method. We support deflate, gzip and bzip2. 

 deflate (RFC1950, RFC1951) and gzip (RFC1952) depend on zlib while bzip2  
 depends on libbzip2. bzip2 is only supported by lynx and some other console 
 text-browsers. 

 We currently limit to compression support to static files. 

 h2. Caching 

 mod_compress can store compressed files on disk to optimize the compression 
 on a second request away. As soon as compress.cache-dir is set the files are 
 compressed. 

 (You will need to create the cache directory if it doesn't already exist. The 
 web server will not do this for you.    The directory will also need the proper 
 ownership.    For Debian/Ubuntu the user and group ids should both be www-data.) 

 The names of the cache files are made of the filename, the compression method 
 and the etag associated to the file. 

 Cleaning the cache is left to the user. A cron job deleting files older than 
 10 days could do it: :: 

 <pre> 
   find /var/www/cache -type f -mtime +10 | xargs -r rm 
 </pre> 

 h2. Limitations 

 The module limits the compression of files to files smaller than 128 MByte and 
 larger than 128 Byte. 

 The lower limit is set as small files tend to become larger by compressing due 
 to the compression headers, the upper limit is set to work sensibly with 
 memory and cpu-time.    In fact, if you are on a low end server, you may get better performance if you disable mod_compress. 

 Directories containing a tilde ('~') are not created automatically (See ticket 
 #113). To enable compression for user dirs you have to create the directories 
 by hand in the cache directory. 

 h2. Options 

 h3. compress.allowed-encodings 

   
   override default set of allowed encodings 

   e.g.: :: 

 <pre> 
     compress.allowed-encodings = ("bzip2", "gzip", "deflate") 
 </pre> 

 h3. compress.cache-dir 

   
   name of the directory where compressed content will be cached 

   e.g.: :: 
 <pre> 
     compress.cache-dir = "/var/www/cache/" 

    
     # even better with virt-hosting 
     $HTTP["host"] == "docs.example.org" { 
       compress.cache-dir = "/var/www/cache/docs.example.org/" 
     } 
 </pre>     
   Default: not set, compress the file for every request 

 h3. compress.filetype 

   
   mimetypes which might get compressed (since 1.4.24 a "simple" filetype also matches "extended" mimetypes, i.e. "text/plain" will compress "text/plain; charset=utf-8" too) 
  
   e.g.: :: 
 <pre>   
     compress.filetype             = ("text/plain", "text/html") 
 </pre> 
   Keep in mind that compressed JavaScript and CSS files are broken in some 
   browsers. Not setting any filetypes will result in no files being compressed. 

   NOTE: You have to specify the full mime-type! If you also define a charset, 
   for example, you have to use "text/plain; charset=utf-8" instead of just "text/plain". 

   Default: not set 

 h3. compress.max-filesize 

   
   maximum size of the original file to be compressed kBytes. 

   This is meant to protect the server against DoSing as compressing large 
   (let's say 1Gbyte) takes a lot of time and would delay the whole operation 
   of the server. 

   There is a hard upper limit of 128Mbyte. 

   Default: unlimited (== hard-limit of 128MByte) 

 h2. Display compressed files 

 If you enable mod_compress, and you want to force clients to uncompress and display 
 compressed text files, please force mimetype to nothing. 
 Example : 
 If you want to add headers for uncompress and display diff.gz files , add this 
 section in your conf : :: 

 <pre> 
   $HTTP["url"] =~ "\.diff\.gz" { 
     setenv.add-response-header = ( "Content-Encoding" => "gzip" ) 
     mimetype.assign = () 
   } 
 </pre> 
  
 h2. Compressing Dynamic Content 

 h3. PHP 

 To compress dynamic content with PHP please enable :: 
 <pre> 
   zlib.output_compression = 1 
   zlib.output_handler = On 
 </pre>   
 in the php.ini as PHP provides compression support by itself. 

 mod_compress of lighttpd 1.5 r1992 may not set correct Content-Encoding with php-fcgi. 
 A solution to that problem would be: 

 1.disable mod_compress when request a php file:: 
 <pre> 
     $HTTP["url"] !~ "\.php$" { 
    	 compress.filetype = ("text/plain", "text/html", "text/javascript", "text/css", "text/xml") 
     } 
 </pre> 
 2.enable mod_setenv of your lighttpd:: 
 <pre> 
     server.modules    += ( "mod_setenv" ) 
 </pre> 
 3.manually set Content-Encoding:: 
 <pre> 
     $HTTP["url"] =~ "\.php$" { 
  	 setenv.add-response-header    = ( "Content-Encoding" => "gzip") 
     } 
 </pre> 

 h3. TurboGears 

 To compress dynamic content with TurboGears please enable :: 
 <pre> 
   [/] 
   gzip_filter.on = True 
   gzip_filter.mime_types = ["application/x-javascript", "text/javascript", "text/html", "text/css", "text/plain"] 
 </pre> 

 in the config/app.cfg file in your TurboGears application.    The above lines 
 should already be in the file.    You just need to remove the comment symbol 
 in front of the lines to make them active. 

 h3. Django 

 To compress dynamic content with Django please enable the GZipMiddleware :: 
 <pre> 
   MIDDLEWARE_CLASSES = ( 
       'django.middleware.gzip.GZipMiddleware', 
       ... 
   ) 
 </pre> 
 in the settings.py file in your Django project. 

 h3. Catalyst 

 To compress dynamic content with Perl/Catalyst, simply use 
 the Catalyst::Plugin::Compress::Gzip module available on CPAN :: 
 <pre> 
   use Catalyst qw( 
       Compress::Gzip 
       ... 
   ); 
 </pre> 
 in your main package (MyApp.pm). Further configuration is not required.