Close discarded connections

[fatkodima]

Currently, when a new connection is created and the connection pool reaches its maximum size, it just removes some old connection, but without closing. So it is possible to end up with lots of lingering opened connections, which will not be reused and waste process' opened fds.

This PR makes sure to close discarded connections.

[jjb]

@tenderlove what do you think?

[pda]

Would these @ques[oldest].pop connections usually be implicitly closed via garbage collection, assuming nothing else is holding a reference to them? Or is there nothing in GC that would release the file descriptors etc?

Edit: I suspect not… I don't always believe LLMs but this sounds fairly legit:

GC may eventually free the object, but there's no guarantee when, and the file descriptor may remain open in the meantime.
Relying on GC for closing FDs is unsafe and will likely lead to file descriptor leaks.