In our app we use sidekiq to process async jobs. For this to work well I've set pool_size to 35 using the latest mongo driver (1.6.1). It works well for all jobs except two types that complain with this error:

``ruby
could not obtain connection within 5.0 seconds. The max pool size is currently 1; consider increasing the pool size or timeout.
`

The model I'm calling the find on inside the worker is the base class for STI if that helps.

Here's the full stack trace:
https://gist.github.com/43a1b0b63749229220b6