Chapter 12: Squid

Overview

Squid is a feature-rich and extremely flexible web-caching proxy daemon. Most configuration is performed by editing a simple configuration file called squid.conf, which is usually located in /usr/local/squid/etc/squid.conf or, on systems derived from Red Hat Linux, /etc/squid/squid.conf. Each behavior is set by a directive followed by one or more options. The Webmin interface provides access to most of the directives available for configuring Squid. Because Squid is a quite complex package, the Webmin interface opens with a series of icons to represent the different types of configuration options.

Figure 12-1 shows the Squid main page.

Figure 12-1: Squid proxy main page

These options are pretty self-explanatory, though a couple of them are worth discussing. The Cache Manager Statistics icon, when clicked, will open the Squid cachemgr.cgi program to provide direct access to all of Squid's various runtime values and statistics. The program provides real-time information about hit ratios, request rates, storage capacity, number of users, system load, and more. The Calamaris Log Analysis icon is only present if the calamaris access.log analyzer is present on your system. Calamaris is a nice Perl script that will parse your access log files and provide a nice overview of the type of usage your cache is seeing. Note that by default the Calamaris Webmin tool will only parse the last 50,000 lines of your access log. This number can be raised in the Squid module configuration, but is not recommended on heavily loaded caches. The parsing of the access logs is a very system-intensive task that could interfere with your system's ability to continue answering requests.