Assembling Pages Last: Edge Caching, ESI & Rails

Edge caching is a technique used to distribute content to cache servers that are closer to the end user, e.g. closer to the “edge”. Edge Side Includes (ESI) is a simple markup language for describing dynamic assembly of applications. At the core, it’s similar to Server Side Includes (SSI), although it is processed at a higher level in the stack. It has been accepted/implemented by a half dozen cache servers which include both open source (Squid, Mongrel-ESI) and commercial (Oracle Web Cache, Akamai, Digital Island) solutions. ESI also includes a caching/invalidation schema, along with exception handling and conditional logic at the edge.

You may have a highly personalized Rails application that you are scaling to millions of users per day. You may also be pushing your legacy applications to rails and want an interim solution for web application assembly that is technology agnostic. ESI can be used as a solution to both.

This talk will cover:

• Common use cases for ESI
• Invalidation strategies
• Exception handling on the edge
• Real code!

We’ll configure a rails application for ESI support. We’ll walk through caching and application assembly use cases, including invalidation, as well as open source and commercial options for deployment.