Memory leaks, cached_model and backend jobs

Eric Hodel | Thu, 24 Aug 2006 21:08:36 GMT

Posted in Rails, Robot Co-op

One of my long-running problems with Rails (and Ruby in general) is that it’s difficult to debug memory leaks. I’ve had a number of cases where I’ve stuck something into a long-lived array or hash and discovered much later that my Ruby process was eating over 100 MB of RAM. While ps makes it easy to see when Ruby’s using lots of RAM, actually figuring out where it went is a lot harder.

[...] I asked the Seattle Ruby Group for help, and Ryan Davis gave me a quick little memory leak spotter that he uses. I made a few additions to it, and it helped me discover that my Typo development tree was leaking 1-3 strings per hit

—Memory leak profiling with Rails via scottstuff: Memory leak profiling with Rails

I just used Scott and Ryan’s script to find a memory leak in our backend jobs related to cached_model. We have the local cache enabled for for our sites because we reset the cache every page request. In our backend jobs we don’t clear the local cache so we end up with a Hash that holding every ActiveRecord object we’ve ever retrieved from the database.

So if the warnings in the documentation weren’t enough, here it is again. If you’re using CachedModel in a backend job, be sure to disable the local cache or call cache_reset periodically to allow items to be garbage collected.

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