Alfa Jango Blog Engineering, Software, and Entrepreneurship

In my last post, I discussed the three techniques used to improve asset load speed. In this post, I will discuss how to combine the use of GZipping and a Content Delivery Network (CDN) for the fastest possible page loads.

Pitfall of Amazon S3 + CloudFront

Everyone’s favorite CDN these days is Amazon’s CloudFront service, which serves files directly from Amazon’s scalable “simple storage system”, Amazon S3. It is very easy to work with, has widespread support in Ruby gems and plugins (and countless other libraries), and is very inexpensive with it’s pay-as-you-go billing.

However, there is one large pitfall to using Amazon S3 + CloudFront, and that is that neither S3 nor CloudFront support GZip detecting and encoding. It would seem that we need to now decide whether we’ll do without GZipping or using a CDN. Not so! There is another way.

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We recently worked on a Rails application that had page and action caching set up, only to find that it was not actually working. It occurred to me that many Rails/Passenger/Apache applications may have caching set up in a way that it appears to be caching, when it is not actually caching. Searching through the interwebs for various Passenger/Apache configurations, such as this snippet on Github or this discussion on Google Groups, I found that many did not work with the most recent version of Phusion Passenger. What’s more, these configurations give the appearance that they are working.

For an introduction to caching with Rails, check out this post: Caching With Rails: An Overview

The Appearance That Caching Works

Here is what I mean by giving the appearance that caching is working:

1. you add caches_page :index to your controller, for example
2. configure and restart your server
3. load the index page
4. check your rails cache directory on your server, and see the index.html
5. it works! (hint: this step is wrong, you’re not quite there yet)

Just because Rails is generating your cached page does not mean that your server is subsequently serving the cached .html file instead of sending the request to Rails again.

Ensure It’s Serving the Cached Page

To make sure it’s subsequently serving the cached page, the easiest method is to look at the created date on the cached file on your server, for instance:

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