Check the wait state for the backend process. I’ve seen this happen when a process ran a per-row trigger that tried to connect to something else, and it filled the ip_conntrack table. So, kernel level wait along with a whole bunch of locks on the table in question.
Running pg_terminate_backend() didn’t work, as the signal queued behind the kernel wait. We had to bounce the database to get rid of the problem. Immediately afterwards we disabled the trigger. HTH, Bob Lunney > On Apr 29, 2016, at 1:30 PM, Ciprian Grigoras <ciprian.grigo...@vitals.com> > wrote: > > Hi guys, > > I had a question. We're running Postgresql 9.0.7 , and all of a sudden we > started seeing unexpected behavior. One table got locked after we ran one > simple INSERT on one test item. > Nothing else was running against that table as far as we know, and the query > is frozen there now. After some time we tried to terminate it forcefully > (pg_terminate_backend), ran that and the return of the command is "true" but > the query still stays on, shows up on pg_stat_activity etc. > Reading from the table is fine, but we believe any other inserts / updates > are not possible. > > Restarting the Postgresql server is not an option at this moment, since it's > a production box and another high-demand database is running from that. > > Has anyone seen a similar issue (maybe a bug in the 9.0 version ?) where > simple statements don't finish and get locked there and can't be killed by > the pg_terminate_backed ? What is the cause of this ? > Any reasonable way to find out more details on what caused this, how to > prevent it in the future, and how it can be fixed sensitively now ? Thanks ! > > just fyi, checking the data in the "pg_locks" (for that process that is > frozen), shows a bunch of rows all with the same virtualtransactionid. Only > one of them has the mode of "ExclusiveLock" (the only record there with a > locktype of "virtualxid"), a few have the "RowExclusiveLock" mode and the > vast majority have the "AccessShareLock" mode. > > Thanks, > Ciprian
