Add to documentation used connections

[VitorTrin]

Our application was using more connections than what we configured for our Repo. We later found out that every job queue uses an exclusive connection, and that caused the strange number of connections.

Somewhere in the documentation it should explained that usage of connections so the user can understand the behaviour of his application.

[mbuhot]

Yes the Postgrex.Notifications listener consumes a DB connection that isn't from the Repo pool.

Where would you expect to see such information? Perhaps in the https://github.com/mbuhot/ecto_job#how-it-works section of the readme?

[VitorTrin]

Yeah, it seems to be the ideal place.