From: | Costa Alexoglou <costa(at)dbtune(dot)com> |
---|---|
To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
Cc: | Christophe Pettus <xof(at)thebuild(dot)com>, pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | Re: Vacuum full connection exhaustion |
Date: | 2024-08-09 09:47:26 |
Message-ID: | CAJ+5Ff4n+3SpSeDGd1UwF7JyvBkgHi7uyz0i+JtisD1m0U-PbQ@mail.gmail.com |
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Lists: | pgsql-general |
On Fri, Aug 9, 2024 at 1:02 AM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> On Fri, 9 Aug 2024 at 02:12, Christophe Pettus <xof(at)thebuild(dot)com> wrote:
> > VACUUM FULL takes an exclusive lock on the table that it is operating
> on. It's possible that a connection becomes blocked on that exclusive lock
> waiting for the VACUUM FULL to finish, the application sees the connection
> stopped and fires up another one (this is common in container-based
> applications), that one blocks... until all of the connections are full of
> queries waiting on that VACUUM FULL.
>
> I also imagine this is the cause. One way to test would be to do:
> BEGIN; LOCK TABLE <name of table>; and see if the connections pile up
> in a similar way to when the VACUUM FULL command is used.
>
> David
>
Thanks folks. David really straight-forward way to test. I validated this,
when I lock the two tables involved in the benchmark the connections are
constantly growing until they reach the `max_connections`
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