Rails app (mod_rails) hangs every few hours

I'm running a Rails app through Phusi开发者_如何学Pythonon Passenger (mod_rails) which will run smoothly for a while, then suddenly slow to a crawl (one or two requests per hour) and become unresponsive. CPU usage is low throughout the whole ordeal, although I'm not sure about memory.

Does anyone know where I should start to diagnose/fix the problem?

Update: restarting the app every now and then does fix the problem, although I'm looking for a more long-term solution. Memory usage gradually increases (initially ~30mb per instance, becomes 40mb after an hour, gets to 60 or 70mb by the time it crashes).

New Relic can show you combined memory usage. Engine Yard recommends tools like Rack::Bug, MemoryLogic or Oink. Here's a nice article on something similar that you might find useful.

If restarting the app cures the problem, looking at its resource usage would be a good place to start.

Sounds like you have a memory leak of some sort. If you'd like to bandaid the issue you can try setting the PassengerMaxRequests to something a bit lower until you figure out what's going on.

http://www.modrails.com/documentation/Users%20guide%20Apache.html#PassengerMaxRequests

This will restart your instances, individually, after they've served a set number of requests. You may have to fiddle with it to find the sweet spot where they are restarting automatically before they lock up.

Other tips are: -Go through your plugins/gems and make sure they are up to date -Check for heavy actions and requests where there is a lot of memory consumption (NewRelic is great for this) -You may want to consider switching to REE as it has better garbage collection

Finally, you may want to set a cron job that looks at your currently running passenger instances and kills them if they are over a certain memory threshold. Passenger will handle restarting them.