Random Musings of an Insane Mind

A while back I wrote a plugin to take care of a particular client traffic problem. As the traffic came in very quickly and unexpectedly, I had only minutes to come up with a solution. As I knew Varnish pretty well, my initial reaction was to put the site behind Varnish. But, there’s a problem with Varnish and WordPress.

WordPress is a cookie monster. It uses and depends on cookies for almost everything – and Varnish doesn’t cache assets that contain cookies. VCL was modified and tweaked, but, the site was still having problems.

So, a plugin was born. Since I was familiar with ESI, I opted to write a quick plugin to cache the sidebar and the content would be handled by Varnish. On each request, Varnish would assemble the Edge Side Include and serve the page – saving the server from a meltdown.

The plugin was never really production ready, though, I have used it for a year or so when particular client needs came up. When Varnish released 3.0, ESI could work with GZipped/Deflated content which significantly increased the utility of the plugin.

If you would like to read a detailed explanation of how the plugin works and why, here’s the original presentation I gave in Florida.

You can find the plugin on WordPress’s plugin hosting at http://wordpress.org/extend/plugins/cd34-varnish-esi/.

Tags: esi, Varnish, wordpress

This entry was posted on Tuesday, January 10th, 2012 at 4:06 am and is filed under Web Infrastructure. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.