Re: BUG #16194: use postgresql's pg_advisory_xact_lock error

On Tue, Jan 07, 2020 at 09:33:26AM +0000, PG Bug reporting form wrote:
>The following bug has been logged on the website:
>
>Bug reference: 16194
>Logged by: andy ye
>Email address: andy(dot)ye(at)gtssz(dot)net
>PostgreSQL version: 9.5.11
>Operating system: ubuntu 16.04
>Description:
>
>When I use postgresql's pg_advisory_xact_lock for transaction security,
>especially RPC services, I often see that the lock is not released, causing
>the service to block for a long time. The blocking time is about 15 minutes.
>

That's rather suspicious. My guess would be that you're not actually
terminating the transaction, it's staying open and so the advisory lock
is not being released. And then ~15 minutes later some sort of timeout
is being hit, closing the connection (e.g. in a connection pool, app
server or something like that) and releasing the lock.

We need to see some sort of debugging info, demonstrating that the
transaction was actually finished (committed/released) and the lock is
still being held. So if you observe this, you need to get the relevant
info from pg_locks and pg_stat_activity.

A reproducer would be very useful, of course.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services