Re: Deadlocks in HS (on 9.0 :( )

On 2014-07-15 16:54:05 +0100, Greg Stark wrote:
> We've observed a 9.0 database have undetected deadlocks repeatedly in
> hot standby mode.
>
> I think what's happening is that autovacuum is kicking off a VACUUM of
> some system catalogs -- it seems to usually be pg_statistics' toast
> table actually. At the end of the vacuum it briefly gets the exclusive
> lock to truncate the table. On the standby it replays that and records
> the exclusive lock being taken. It then sees a cleanup record that
> pauses replay because a HS standby transaction is running that can see
> the xid being cleaned up. That transaction then blocks against the
> exclusive lock and deadlocks against recovery.

Hm. Does that resolve itself after max_standby_streaming_delay? Because
I don't really see how it'd actually have an undetected deadlock in that
case.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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