[pgpool-general: 1206] Semphore errors after adding/removing hosts?

Nick Webb nickw at redwireservices.com
Sat Dec 1 09:41:40 JST 2012


Hello,

I'm fairly new to pgpool, but am already quite a fan, thanks for the great
software!

When using the pcp_detach_node command followed by pcp_attach_node after
doing some maintenance on a backend, I start getting errors like this in
the log:

Nov 27 03:09:02 PGLB pgpool-X[32282]: semop(id=884737) failed: Invalid
argument
Nov 27 03:09:02 PGLB pgpool-X[10230]: semop(id=884737) failed: Invalid
argument
Nov 27 03:09:02 PGLB pgpool-X[10230]: semop(id=884737) failed: Invalid
argument

These continue over and over until the process is restarted.

I ignored them when I first saw it, as it seemed to function just fine, but
a few days later our application could not connect to PGPool very well, it
was very slow and most connections timed out despite the system load and
CPU being very low.  Connections from the PGPool host to
the back-ends directly were also very quick (via psql command).

Stopping and starting PGPool immediately returned the service to normal
performance levels.

Are these two issues linked?  How can I stop from getting the semop error
when attaching hosts?

It also seems that about every 3rd or 4th pcp_ command I run hangs,
seemingly waiting until open connections finish... and I think it finish
after a few minutes.  This may be related, as I seem to recall one of these
"hangs" when adding the backend back to the pool, then seeing the semop
errors (could have been the detach that hung, not sure).

Thanks!

Nick
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