Is there a way to get pg_stat_activity information without using an SQL connection?

Question

pg_stat_activity holds extremely useful information for post-mortem analysis of various issues, especially concurrency-related, and so augmenting errors or logging

Answer 1

Not really, but the parameter superuser_reserved_connections will help you. It defines the number of connections that are reserved for superusers precisely so that they can still connect, even if the connection limit is exhausted.

Set the value high enough and have your monitoring process connect as superuser.