Re: Occasional 9.6.10 PMChildFlags fatal error, possibly due to >2 parallel gathers

On Wed, Feb 13, 2019 at 3:41 PM Chris Snook <csnook(at)cloudflare(dot)com> wrote:
> For more context, I got these tightly packed around the first crash, with the first and last messages repeated hundreds of times:
>
> FATAL: sorry, too many clients already
> FATAL: sorry, too many clients already
> FATAL: sorry, too many clients already
> FATAL: no free slots in PMChildFlags array
> WARNING: could not remove shared memory segment "/PostgreSQL.1407760088": No such file or directory
> FATAL: semop(id=2293786) failed: Invalid argument
> FATAL: semop(id=2293786) failed: Invalid argument
> FATAL: semctl(2064403, 7, SETVAL, 0) failed: Invalid argument
> FATAL: semop(id=2621476) failed: Invalid argument
> FATAL: semop(id=2621476) failed: Invalid argument
> FATAL: semctl(2293786, 1, SETVAL, 0) failed: Invalid argument
> FATAL: semctl(2621476, 10, SETVAL, 0) failed: Invalid argument
> WARNING: could not remove shared memory segment "/PostgreSQL.1621779631": No such file or directory

Any chance you created a cronjob that runs as user "postgres" (or
whatever user the PostgreSQL cluster runs as), or logged in as that
user manually for some reason? Systemd likes to blow away global IPC
resources associated with users when they log out.

https://www.postgresql.org/docs/11/kernel-resources.html#SYSTEMD-REMOVEIPC

--
Thomas Munro
http://www.enterprisedb.com