Re: Idle in transaction help

Scot Kreienkamp wrote:
>
> Hi everyone,
>
> I need some help with tracking down idle in transaction problems. We
> have a custom application that is leaving queries in idle in
> transaction status for unknown reasons. The developers are working on
> ways to track it down, but right now the options on their end are
> limited and it will be at least 1-2 months until they have something
> working. I am trying to track down the problem from the PG end in the
> meantime. Is there any way to tell what query is hanging in idle in
> transaction status? Or what the current or previous query was/is,
> since idle in transaction doesn’t tell me anything? I’m kind of at a
> loss on what if anything I can do from the database end to help (read
> push) the programmers to find and fix this problem.
>

there is no active query, thats why its idle. they did a "BEGIN" to
start a transaction, then left the connection idle.

is this software, by any chance, Java based? older versions of the
Postgres JDBC module had a nasty habit of doing this, as JDBC
autogenerates the BEGIN if its not in autocommit mode. the older version
would generate the begin immediately after a COMMIT or ROLLBACK to
prepare for the next transaction, and if the app simply stopped using
the connection, it was left IDLE IN TRANSACTION. The updated version
postpones the BEGIN until you issue your first query.

if you enable statement logging and set up a log prefix to show the
Process ID (and I usually prefix with a timestamp, database name and
other useful stuff), then you can grep the logs for the PID of the IDLE
IN TRANSACTION process. Note logging all statements is pretty CPU and
disk intensive, so likely will impact your system performance, so should
only be done for debug purposes.