On Sat, 12 Jan 2008, Craig James wrote:

>> You can unlock it with the UNLOCK SET command.  You can find it here in the 
>> docs:
>> 
>> http://slony.info/documentation/stmtunlockset.html
>
> Thanks, Jeff, you saved my day.

I've had it happen to me before as well.  Interestingly, after unlocking the 
set in the past, I've been able to successfully lock and move the set almost 
immediately afterwards.  That was a few revisions of slony back though, so 
your mileage may vary.

>> I'd check the logs to see if there are any clues as to why the move set 
>> failed to complete.
>
> Nothing jumps out at me.  On the master node, there's nothing at all during 
> the time the script was running.  Just a bunch of "DST DEBUG1 cleanupThread" 
> events, nothing else.
>
> On the slave node, there are some messages; maybe the attached logfile will 
> mean something to you.
>

It looks like it was successfully syncing prior to you killing it and 
restarting postgres, but we've only got about a minute's worth of log data 
here.  It would probably be interesting to see immediately after you started 
the move set.  You might need to grep out the uninteresting bits.

> One fact I discovered: The clocks on the two machines were badly out of sync, 
> about 30 minutes.  I assume this is a Bad Thing?

It's officially listed as a requirement here: 
http://slony.info/documentation/requirements.html

You might check the slon logs for any indication this is what caused your 
problem.  I thought slon did its work based entirely on xxid, but I could be 
wrong.  Perhaps one of the developers will comment.  In any event, I'm sure 
you know the clocks should be in sync as a best practice.

>
> Another fact: After the migrate-node operation failed, I had to restart 
> Postgres because one Postgres process was using 100% CPU, and several hundred 
> other processes were waiting on SELECT statements -- the CPU was rapidly 
> getting wedged and wasn't far from locking up altogether.  (These were 
> web-site visitors trying to do queries, each one caused another blocked 
> process.)
>
> So the "lost connection" message may be when I shut down Postgres.
>
>> BTW, what version of slony are you using?
>
> Version 1.2.9, Postgres 8.1.4.

You should upgrade both.  The postgresql 8.1 branch is up to: 8.1.11, so that 
puts you 7 revisions back.  There are lots of important bug fixes in those 
revisions.  Upgrading to 8.1.11 is relatively painless as it can be done in 
place.  You should probably consider upgrading to 8.2.6 when you have a 
chance.

Slony is up to 1.2.12 and also has lots of important bug fixes in 
those revisions.

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