Re: Help: 8.0.3 Vacuum of an empty table never completes ...

On Nov 28, 2005, at 4:13 PM, Tom Lane wrote:

> Yeah, could be.  Anyway it doesn't seem like we can learn much more
> today.  You might as well just zing the vacuumdb process and let
> things get back to normal.  If it happens again, we'd have reason
> to dig deeper.

Final report [ and apologies to hackers list in general -- sorry for  
the noise today ].

Killed the vacuumdb frontend. Then went off killing processes spawned  
by cron on Nov25th related to the cronjob. All of the related  
backends exited peacefully, and all is well. Manual vacuum verbose  
analyze completes successfully.

One possibly curious thing -- one final process remains on the backup  
box dated Nov25:

root     19912     3  0 Nov25 ?        00:00:12 [pdflush]

Coincidence? This is some sort of kernel thread, right? Flushes dirty  
pages to disk? There are two on this machine:

root      9211     3  0 Nov22 ?        00:02:56 [pdflush]
root     19912     3  0 Nov25 ?        00:00:12 [pdflush]

The Nov25'ths pdflush's pid is suspiciously close to the pids which  
would be in use around the beginning of the cron'd process. [ checks / 
var/log/messages ... ] -- yep -- real close -- last known cross- 
referencable pid is:

Nov 25 04:59:01 db02 /usr/sbin/cron[20590]: (root) CMD ( rm -f /var/ 
spool/cron/lastrun/cron.hourly)

and the vacuumdb sshd connection on the production db box is logged  
at 05:02:22 AM, so that pdflush would have been started real close to  
the time which the remote backup + vacuum script would have been  
running.

Any Linux 2.6 gurus lurking? Under what circumstances do pdflush'es  
get spawned? The filesystem upon which the outputs were going is a  
software raid partition (raid-0? raid-1? Always confuse the two) --  
the interleaved one anyway, not mirrored -- formatted reiser3.

Neither pdflush instance on this machine was started anywhere near  
the boot time of the machine -- both much later. Whereas on the  
production box the two pdflush instances are both dated from machine   
boot time. Does this perchance indicate unhappiness afoot perhaps  
hardware-wise?

----
James Robinson
Socialserve.com