Re: does wal archiving block the current client connection?

On Fri, 19 May 2006, Tom Lane wrote:

> Well, there's our smoking gun.  IIRC, all the failures you showed us are
> consistent with race conditions caused by multiple archiver processes
> all trying to do the same tasks concurrently.
>
> Do you frequently stop and restart the postmaster?  Because I don't see
> how you could get into this state without having done so.
>
> I've just been looking at the code, and the archiver does commit
> hara-kiri when it notices its parent postmaster is dead; but it only
> checks that in the outer loop.  Given sufficiently long delays in the
> archive_command, that could be a long time after the postmaster died;
> and in the meantime, successive executions of the archive_command could
> be conflicting with those launched by a later archiver incarnation.

Hurray!  Unfortunately, the postmaster on the original troubled server almost
never gets restarted, and in fact only has only one archiver process running
right now.  Drat!

I guess I'll have to try and catch it in the act again the next time the NAS
gets wedged so I can debug a little more (it was caught by one of the windows
folks last time) and gather some useful data.

Let me know if you want me to test a patch since I've already got this test
case setup.

--
Jeff Frost, Owner     <jeff@frostconsultingllc.com>
Frost Consulting, LLC     http://www.frostconsultingllc.com/
Phone: 650-780-7908    FAX: 650-649-1954