Rails Cookbook

Chapter 12. Performance

Introduction

Discussing web application performance is complicated. There are many different aspects to performance, not the least of which is the user’s perception: does the end user think the application is slow or fast? If she thinks it’s fast, she doesn’t care (though you may) that your servers are being pounded to death. On the other hand, a user with a slow Internet connection is likely to perceive your application as slow, even if your servers are running nicely. Of course, you don’t have any control over the user’s Internet connection or, for that matter, over her perceptions. Nevertheless, you usually want to make sure your application is as responsive as the most popular sites on the Internet that have a similar amount of content. Of course this is a very general goal and has more to do with what users are likely to expect than what your application may have to go through to generate its content.

For example, you may have an application that does some very complex reporting against a large set of data. Dynamically generating these reports may take a significant amount of time. Your users, on the other hand, expect that you should have solved this problem somehow and would like to see most pages returned in about the same time as it takes to render static HTML.

Think for a moment about the fastest web application you could write. It may be a CGI program written in C. In this case, the performance bottleneck would likely not be the application itself ...