I gave mongoid 5 a try in my app.

The rails side is working without problems, but the sidekiq process is constantly opening connections.
Only if I restart the process, the connections get closed.

I get the value from mongodb serverStatus.connections.current metric.

I use the following client settings in mongoid.yml:

max_pool_size: 100
min_pool_size: 30

As I only upgraded the mongoid gem, I assume the problem is not depending on sidekiq.