James Sewell <james.sewell@xxxxxxxxxxxx> writes: > 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 What are you looking at to claim the number of connections is under 600? Maybe there's some disconnect between what you're measuring and what the database thinks. A different line of thought is that ProcArray slots can be consumed by things that aren't client connection processes, in particular (1) parallel-query workers (2) autovacuum workers Looking into pg_stat_activity when you see this issue might help clarify that. regards, tom lane
