Emit a 'release' event when a connection is released back to the pool

[nihonjinrxs]

This PR has the Pool object emit a 'release' event upon the release of a client/connection back to the pool.

We're experiencing an issue that feels quite similar to what's described in #2262, and in reading through the comments there, I was interested to see @brianc's suggestion of adding a 'release' event as the corresponding bookend to the 'connect' and 'acquire' events. However, in searching the code, it seems this was never implemented, so I've implemented that here.

[nihonjinrxs]

@brianc let me know if you need anything more from me on this. Happy to help get this merged in whatever way you need. Thanks!

[weyert]

Nice, looks like this could also be used to count the number of open connections?

[nihonjinrxs]

Nice, looks like this could also be used to count the number of open connections?

@weyert You could, but I think it's probably easier to use the existing properties totalCount and idleCount to understand connection count in the pool. There's also a waitingCount which counts requests waiting for a connection to be available.

If you wanted to do it via events, there are also existing events emitted:

• connect when a new connection is made to postgres
• remove when a connection is dropped from the pool

What this PR adds is the balancing release event for the acquire event which is emitted when an existing connection in the pool is acquired to perform a query.

[brianc]

This looks perfectly good to me! Thank you so much! Agree the symmetry here is nice and kinda long standing silly oversight on my part to not do that to begin with. 😄 ❤️

[brianc]

okay weirdly....the tests don't seem to have run for this PR? Would you be able to try rebasing on master and see if they run at that point? Since it's a net addition only with like 1 line of change and good test coverage I can also just pull it and run them manually if you don't have time....though I do like every PR to go through CI.

[nihonjinrxs]

Hey @brianc -- sorry for the delay in getting back to this. I've synced my fork, and CI seems to be running. Thanks!

[nihonjinrxs]

@brianc Any chance we can get this one merged soon?

[nihonjinrxs]

Hey, @brianc -- sorry to ping again, but it's been a while. Hoping to get this PR merged soon. We're currently operating off of a local branch incorporating this change, and I'd really like to be able to come back to the origin distribution if possible. Let me know if you need anything from me to make this happen. Thanks!

[nihonjinrxs]

@brianc just checking in again -- would love to get this PR merged soon, so we can get off this branch build. Let me know if there's anything more you need here.

[brianc]

sorry for delay! Will release it today!