How to Improve Web Performance and Scalability using Varnish

Varnish Cache

Varnish is a state-of-the-art, high-performance HTTP accelerator. It uses the advanced features in Linux 2.6.  Varnish supports Edge Side Includes, ESI. Edge side includes allow you to break your pages into smaller pieces, and cache those pieces independently.

Default start up

 varnishd -a :80 -b localhost:8080 -T localhost:6082 -s file,/var/cache/varnish.cache,256M

 varnishd -a 192.168.1.16:80 -b localhost:80 -T localhost:6082 
          -s file,/var/cache/varnish.cache,256M

-a gives the IP:port varnish should listen on, 
-b gives the IP:port of the backend handling web server

To stop varnish

 /etc/rc.d/init.d/varnish stop

Scaling PHP applications with Varnish

• Article from IBM

Using Varnish with Drupal

• Drupal  will serve content to authorised, logged in users, as well as anonymous users on the same URL.
• Drupal 7 supports the basic cache-control headers which are necessary to use Varnish as a cache for full pages. Pressflow backports this functionality to version 6.x for those who need it.

• Drupal Module Varnish HTTP Accelerator Integration

• Step-by-step: Setting up Varnish, Apache, APC and Solr Project Mercury Style

When setting up varnish using the default configuration in front of your application (in my case : a PHP app), you’ll probably notice that varnish caches nothing.

An example setup of Varnish, Apache and MediaWiki on a single server outlined.

Varnish logs and other notes

Drupal performance and scability

Video from Drupalcon

RPM for Varnish

Sites that use Varnish

Twiter, Facebook, Wikipedia, Hulu, Drupal.org