troubleshooting a database that keeps locking up

Jonathan Vanasco <postgres@2xlp.com> writes:

I have a database that has started to constantly hang after a brief period of activity

looking at `select * from pg_stat_activity;` I roughly see the following each time:

process 1 | <IDLE>
process 2 | <IDLE> in transaction
process 3 | <IDLE> in transaction
process 4 | <IDLE>
process 5 | <IDLE>
process 6 | <IDLE>
process 7 | INSERT INTO table_a ........ RETURNING id

Does anyone have tips on how I can troubleshoot this.

It's a reasonable bet that process 7 is blocked waiting for a lock that's
held by one of the idle-in-transaction processes. You could look into
pg_locks to confirm that.

I was hoping there would be some way to show the history of the "<IDLE> in transaction" processes, but I couldn't find them.

No, PG doesn't track that. You could turn on log_statement = all and
then look to the postmaster log to see what those processes had been
doing. (You'll probably want to set log_line_prefix to at least %p
if you haven't already.)

regards, tom lane

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