lighttpd In-Memory gzip Compression

Posted 2009-04-20 in WWW by Johann.

gzip compression improves website performance by decreasing the size of files. The efficiency of gzip can be increased by using an in-memory file system.

Web Application Performance Tuning Targets

There are three goals when tuning the performance of websites:

1. Making less requests. Requests can be saved by inlining CSS and CSS sprites.
2. Avoiding duplicate requests. This is what caching headers are used for.
3. Reducing the amount of data. Either by removing whitespace or unnecessary code or by compressing the data.

Configuring lighttpd

lighttp supports transparent gzip compression out-of-the-box with the mod_compress module. Enable it in /etc/lighttpd/lighttpd.conf like this:

server.modules = (
    "mod_accesslog",
    "mod_access",
    "mod_redirect",
    "mod_rewrite",
    "mod_evhost",
    "mod_proxy",
    "mod_compress",
    "mod_expire"
)

The next step is to set up a directory in an in-memory file system that caches the compressed version of the files.

# mkdir -p /dev/shm/lighttpd/compress
# chown -R www-data:www-data /dev/shm/lighttpd

Configuring mod_compress consists of specifying the cache directory and the MIME types of the files to compress. In my example, I’m compressing plain text files, static web pages, CSS style sheets and JavaScript files.

compress.cache-dir   = "/dev/shm/lighttpd/compress"
compress.filetype    =
 ( "text/plain", "text/html", "text/css", "text/javascript" )

After restarting lighttpd, gzip compression is active. Of course, only user-agents that ask for gzip-compressed content using an Accept-Encoding HTTP header will be served the gzip compressed files.

To make sure the in-memory directory exists after reboot, add the commands above to /etc/rc.local.

Real-Life Examples

Here are two real-life examples how much data can be saved using gzip compression:

nebel.org

NEBEL consists of very few elements.

1. /index.html was compressed to 2.6 KB from 15.6 KB.
2. https://johannburkard.de/resources/css/r5.css was compressed to 2.4 KB from 8.3 KB.

The total bandwidth saving is 18.9 KB.

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