Re: kevent latch paths don't handle postmaster death well

On 14/10/2020 21:58, Tom Lane wrote:
> I noticed that chipmunk failed [1] with a rather interesting log:
> 
> 2020-10-14 08:57:01.661 EEST [27048:6] pg_regress/prepared_xacts LOG:  statement: UPDATE pxtest1 SET foobar = 'bbb'
WHEREfoobar = 'aaa';
 
> 2020-10-14 08:57:01.721 EEST [27048:7] pg_regress/prepared_xacts LOG:  statement: SELECT * FROM pxtest1;
> 2020-10-14 08:57:01.823 EEST [27048:8] pg_regress/prepared_xacts FATAL:  postmaster exited during a parallel
transaction
> TRAP: FailedAssertion("entry->trans == NULL", File: "pgstat.c", Line: 909, PID: 27048)
> 2020-10-14 08:57:01.861 EEST [27051:1] ERROR:  could not attach to dynamic shared area
> 2020-10-14 08:57:01.861 EEST [27051:2] STATEMENT:  SELECT * FROM pxtest1;
> 
> I do not know what happened to the postmaster, but seeing that chipmunk
> is a very small machine running a pretty old Linux kernel, it's plausible
> to guess that the OOM killer decided to pick on the postmaster.  (I wonder
> whether Heikki has taken any steps to prevent that on that machine.)

For the record, it was not the OOM killer. It was the buildfarm cron job 
that did it:

Oct 14 08:57:01 raspberrypi /USR/SBIN/CRON[27050]: (pgbfarm) CMD 
(killall -q -9 postgres; cd /home/pgbfarm/build-farm-client/ && 
./run_branches.pl --run-all)

Apparently building and testing all the branches is now taking slightly 
more than 24 h on that system, so the next day's cron job kills the 
previous tests. I'm going to change the cron schedule so that it runs 
only every other day.

- Heikki