We're in the process of upgrading our application to use the Mongoid 5 gem so that we can eventually upgrade to Mongo 2.6.

As soon as we deployed with Mongoid 5, the number of open connections seems to grow rapidly.

We suspect its related to our specific application, which uses Rails and has Sidekiq for async processing - our guess is that the async worker connections are not being terminated correctly by Mongo, leading to an ever growing pool of connections, but this seems to be a problem with Mongoid/Mongo, not with Sidekiq.

There's a thread about this here on the Mongoid support forums, but it appears to only be fixed in Mongoid 6: https://jira.mongodb.org/browse/MONGOID-4253

Any ideas on what might be causing this to happen / possible solutions?