Ronin: A Simple Rails Process Logger

Tieg Zaharia — Thu, 20 Mar 2008 16:39:00 +0000

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Back in the fall at rmbr we were running into some requests that ate up a bunch of our memory. Since we often call a few dozen xml requests at a time, we weren’t exactly sure at first which requests were the cause of the growth.

Since I didn’t have a lot of experience with the already-existing Ruby performance tools out there, I cooked up a really basic plugin that monitors the growth of your Rails handler (server-agnostic, although I’ve only used it with Mongrel). We found the greedy requests and traced the leak to some SQL that was being loaded in one of our views (naughty!) within a few minutes of putting the plugin up on our server.

I finally got around to putting this plugin in my repository, so here is how you can try it out:

script/plugin install http://solid1pxred.com/svn/code/rails/plugins/ronin

Try it locally by running your server likes this:

RONIN=on script/server

And then just tail the log to watch your requests:

tail -f log/ronin.log

The plugin outputs the stats like so:

{ :growth => 0.22, :request_time => 0.187, :start_rss => 23416, :end_rss => 30076, :delta_rss => 6660, :uri => '/zombies/4.xml' }

As you can see it is pretty simple to load the log into irb, eval it, and sort it or do whatever you want with it. I’ve noticed a discrepancy with the request time against the Rails logger, so this is by no means scientific (yet… ?), but it gave me a really good approximation to detect those requests that make your server processes grow.

NOTE: this currently is built for POSIX systems

border: solid 1px red;: Ronin: A Simple Rails Process Logger

Ronin: A Simple Rails Process Logger