Why is default_session removed from the releases?

[TravisSpangle]

I have a project to upgrade a rails app (rails 4.2) using mongoid 4. In upgrading to mongoid 6 I am getting a slew of errors

NoMethodError:
  undefined method `default_session' for Mongoid:Module
  Did you mean?  default_client

I saw that it was removed in this commit but haven't seen documentation on why and what else should be used. I'm concerned about the compatibility since I don't see a list of deprecations.

Any advice on how to move forward? I'm not sure if I'm supposed to use a different gem or if this application is stuck using mongoid 4.

[TravisSpangle]

Looking through that commit I was able to swap default_session our with default_client. Then update the parameters called to default_client.with to a nested hash structure.

Mongoid.default_session.with(read: :primary)

# to

Mongoid.default_client.with({ read: { mode: :primary } })