Or something like that. I’ve upgraded several apps from Rails 3.0 to Rails 3.1. They are are running on Thin with the multithreaded option enabled, they are all configured with threadsafe!. Worked great in Rails 3.0. But in 3.1, after a few requests, things start slowing down. After a few more requests, the pages hangs for N seconds (where N is my db timeout) and I get this error:
ActiveRecord::ConnectionTimeoutError (could not obtain a database connection within 5 seconds. The max pool size is currently 5; consider increasing it.):
Those default values of 5 and 5 have been find in the past and should still be fine. Also increasing them does not fix the problem, though it takes a little longer to manifest. I should stress that during these times I have been the only one accessing the apps. When I drop Thin down to single-threaded mode, everything works as expected.
This occurs with MySQL, SQLite, Ruby 1.8.7 and Ruby 1.9.2. Thin is unchanged. The only variable I can find is the upgrade to Rails 3.1. Is there anything I can do, or is this a regression in Rails?
Looks like this is a bug. There’s a patch and pull request for it. Hopefully Rails will merge it in. Until then, multi-threaded Rails apps won’t work on Thin.
https://github.com/rails/rails/pull/1670