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Debian Squeeze (yeah, I know), postgresql 9.1. Two similar db servers, one master one shard. postgresql.conf identical between the two besides small memory footprint config differences - all vacuum/autovacuum configs identical. On both, I have autovacuum workers set to seven. On the shard, ps shows seven happy little workers. On the master, I only have the launcher process -  postgres@mia-main-primary: ~ $ ps -ecf|grep [a]utovacuum postgres 7071 7065 TS 19 13:30 ? 00:00:02 postgres: autovacuum launcher process

I've straced the launcher process on both, and there's little difference, except that the shard spends more time in looping timeout cycles, which sort of makes sense to me since it has actual workers to poll. I've restarted postgresql, no change, nor with changing the number of workers, the aggressiveness, anything.

What's even more curious is that the statistics activity for autovacuuming does show tables being autovacuumed - at least the most active tables.

I'm kind of at a loss. Even though I have the evidence that autovacuuming is happening, I feel uneasy not seeing the actual workers there, particularly when there's no material difference between the two servers.

Thoughts?

  • Turn log_autovacuum on. I'd say it's just running fast enough that you don't notice the workers during their lifetime. – Craig Ringer Dec 18 '15 at 9:26
  • Hmm, possible but probably not probable I think - they are pretty busy servers, and the worker processes remain persistent on the shard server. I'll give log_autovacuum a try though, thanks.! – anastrophe Dec 18 '15 at 16:09
  • I'll be darned. Yep, autovacuum is happily running according to log_autovacuum. I guess it makes sense - the master does much less work than the shard - most of the transactions happen on the latter, with mostly housekeeping happening on master. Thank you for directing me to what should have been the obvious answer! – anastrophe Dec 18 '15 at 18:20

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