Fwd: [LibPQ] Trying PQconnectStart: it doesn't seem to connect

What's wrong with psycopg2 for this purpose?

Python's threading support (in the standard CPython interpreter) is awful due to the global interpreter lock. However, it works for waiting on blocking sockets as the GIL is released before entering most C-language routines. So you should be able to use psycopg2 in dedicated I/O worker threads just fine.

If you're trying to use non-blocking sockets and select(...) with libpq, well, _then_ you'll have to go outside psycopg2. Be aware, though, that using SSL sockets in a non-blocking manner can be ... complicated ... so look into that in detail before deciding on this path. Multiple threads with blocking connections is likely to be a LOT easier.

Frankly, though, you're never going to get wonderful results out of this. Twisted tries, but you've probably seen the issues it has working around the GIL and the limited success it has doing so. CPython's GIL dooms it to be a pretty shoddy language for high concurrency use, whether you use an async socket server model or a blocking threaded model.

You can't reliably verify that a connection is alive with select/poll. TCP/IP timeouts are very long and until the connection times out at the TCP/IP level, it might appear fine even though the peer died hours ago.