I build a lot of Rails apps on a regular basis and each one I add to my server takes another bite out of my limited resources. The way I’ve traditionally setup a new Rails app was using a Mongrel cluster. I found it to be a lot more reliable and faster than the fcgi approach people use to use (and some still do). The downside to setting up a few dozen Rails apps on your server with each running a Mongrel cluster is that it eats up all your memory. One of my sites is starting to get a lot more traffic than it has been in the past and its putting additional strain on the server. As a result I decided to find an alternative to Mongrel. I’ve tried searching for alternatives in the past but everything sent me back to Mongrel. Until today of course when I came across Jamie Flournoy’s blog about mod_rails.
Excited for an alternative to raising a pack of resource hungry mongrels on my server I installed the gem and tried it out. It was exactly what I was looking for as far as ease of use straight away. All I needed to do was stop a mongrel cluster and simplify its virtual host directive in Apache to leave out the mod_proxy_rewrite and the other wonky rewrite rules. The first app I tested went smoothly but suddenly the server started misbehaving. Resources were being eaten and it wasn’t clear what was doing it because the app I was testing with is behind an Apache password and I’m the only user. I ended up having to turn off the mod_rails to get my system back in control. The problem turned out to be that by default mod_rails tries to test if your virtual host directory is a rails app or not. I have a few apps that I tossed in an instance of WordPress into a blog directory inside my rails app directory. I found it convenient to toss them all into the same directory since its all the same website. As a result mod_rails was doing a ../ check to see if the blog directory was a rails app which it decided it was. That’s where the craziness came in because its a php application. Anyway, the quick solution was to move the blog directory out of the Rails app directory.
Other than that my memory usage is way down. I’ve migrated all my low traffic sites to mod_rails and I’m happy with how they’re performing. There is a little delay on the initial load of the app but subsequent calls are quick because its already loaded. I can wait an extra 2-5 seconds for my low traffic apps to load in exchange for hundreds of extra megs of free memory.
I haven’t moved over my higher traffic money making sites yet and I’m not entirely sure I will until I’ve tested mod_rails a bit more. I’m extremely happy with the results thus far though.