Hi,
This is a bit of an odd one - I'm on PostgreSQL 11.9 with a single streaming replica.
The system handles a lot of connections - we have a max_connections of 600. Most are long lived JDBC, but there are a lot of ETL / ad-hoc jobs etc.
Connections normally sit at 300ish, with 70 active at the most. The machines have 32 CPU cores . PgBouncer is sadly not an option hereas we are using many long lived connections which make use of prepared statements.
Sometimes a strange condition occurs. The number of connections is well under 600 (and dropping), but new connections are not being allowed into the database, I can see this message in the logs:
(0:53300)FATAL: remaining connection slots are reserved for non-replication superuser connections
From ps I can see a lot of processes like this:
postgres: accessor monitoring 10.10.7.54[41655] startup
The number of these grows, and no new connections are allowed in. These startup connections do not appear in pg_stat_activity so I can't find what they are waiting on.
Removing some long lived connections sometimes appears to help clear the startup processes and return the system to normal - but I have not been able to find a correlation. It's more blind luck at the moment.
Any pointers on where I could start prodding?
Cheers,
James
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