In January 2008 the site added its first Squid cache server to reduce the load on the primary and only content server. This page explains the steps necessarily to setupand maintain such a server.
Squid ConfigurationEdit
The relevant settings for Squid 2.6 are as follows:
squid.confEdit
# A transparent cache on port 80 with virtual host name support
http_port 80 defaultsite=uesp.net vhost
# The one cache source, content1.uesp.net
cache_peer 72.55.146.206 parent 80 0
# Allow anyone to access the cache
acl validdst dstdomain .uesp.net
http_access allow validdst
# Allow the source and localhost to purge the cache
acl content1 src 72.55.146.206
http_access allow purge localhost
http_access allow purge content1
http_access deny purge
# This must come after the previous lines
http_access deny all
# Rotate logfiles daily and keep up to 10 days
logfile_rotate 10
cachemgr.confEdit
To allow the cache manager to access the Squid cache only one line is needed:
localhost:80
Apache ConfigEdit
To access the Squid cache manager via the web Apache, or a similar web server, must be properly configured. Since this is not meant to be used publically only a minimal web server is needed. The following is for Apache v2.2.
# The Squid cache is on port 80 so choose another unused port
Listen 81
ServerName squid1.uesp.net:81
# Only allow a few potential clients to minimize RAM/CPU use
StartServers 1
MinSpareServers 1
MaxSpareServers 3
ServerLimit 3
MaxClients 3
# Allow access to the Squid cache manager
ScriptAlias /Squid/cgi-bin/cachemgr.cgi /usr/lib/squid/cachemgr.cgi
# Password protect access to the cache manager
<Location /Squid/cgi-bin/cachemgr.cgi>
AuthUserFile /etc/apacheauth
AuthGroupFile /dev/null
AuthName "User/Password Required"
AuthType Basic
require user cachemanager
# Optionally limit access from only certain IPs/domains
order allow,deny
allow from someplace.com
</Location>
MediaWiki ConfigurationEdit
LocalSettings.phpEdit
# Enable use of the Squid cache
$wgUseSquid = true;
# Set the list of caches for purging purposes
$wgSquidServers = array("72.55.137.132");
TestingEdit
Load up FireBug or a similar utility capable of viewing HTML request/response headers. Load up a page as an anonymous user (not logged in) and look for the following lines in the request header:
Cache-Control s-maxage=18000, must-revalidate, max-age=0 X-Cache MISS from cl-t021-251cl.privatedns.com X-Cache-Lookup MISS from cl-t021-251cl.privatedns.com:80
The s-maxage parameter tells the cache how long to cache the page and the default can be changed if desired in LocalSettings.php. A MISS indicates the file was not loaded from the cache while a HIT indicates that it was.
You can view the average cache hit rate by logging into the cache manager and viewing the Cache Utilization entry. The parameters of most interest are:
client_http.requests = 46.309993/sec client_http.hits = 22.639997/sec
This indicates that almost half of all requests are being successfully served from the cache.