ConnectionPool does not close idle connections about mysql

[trowski]

I just replaced the pool implementation in v0.3.0, but this is still an issue in the new implementation. I'll look into adding a timer that closes connections after a period of time. Same in the postgres library.

[rdlowrey]

Y'all probably already know this but sharing for general info and posterity here ...

The approach that's works well for this kind of thing in aerys is having each connection carry its own "state" object with a lastUsedAt timestamp (or equivalent). Then there's a single timer watcher for the pool that triggers once per second to iterate over all open connections that aren't awaiting a response from the other party to check if (now - lastUsedAt) > configurableClientLevelIdlenessTimeout ...

In general it's important to avoid individual per-connection timers because: overhead.

[trowski]

@rdlowrey Yeah, that's the approach I was going to take. The pool implementation has a queue of idle connections where the most recently used goes at the end, so I should be able to just iterate from the front, removing connections as necessary. A busy pool would only need to examine a single connection.

[kelunik]

@rdlowrey it's an optimization, it's not actually important. A userland MySQL client has other bottlenecks.

[brstgt]

That's done, right?