Too Many Clients Already / Connection Slot Exhaustion

[pyramation]

issue for pgsql-test

Summary

Postgres intermittently throws:

sorry, too many clients already

or

remaining connection slots are reserved for roles with the SUPERUSER attribute

indicating the test framework is exhausting available connections.

Cause

Unclosed or overlapping connections during parallel tests, or a low max_connections limit. It could be failing/breaking tests eat connections and we need to clean those up.

temporary fix / debug:

-- List all current connections
SELECT pid, usename, state, query
FROM pg_stat_activity;

-- Terminate all idle connections
SELECT pg_terminate_backend(pid)
FROM pg_stat_activity
WHERE state = 'idle' AND pid <> pg_backend_pid();

-- (optional) terminate all except your current one
SELECT pg_terminate_backend(pid)
FROM pg_stat_activity
WHERE pid <> pg_backend_pid();