Re: Re: Clarifying "server starting" messaging in pg_ctl start without --wait

* Michael Paquier (michael(dot)paquier(at)gmail(dot)com) wrote:
> On Thu, Jan 19, 2017 at 5:01 AM, Peter Eisentraut
> <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
> > On 1/18/17 8:25 AM, Stephen Frost wrote:
> >> I was actually thinking about it the other way- start out by changing
> >> them to both be 5m and then document next to checkpoint_timeout (and
> >> max_wal_size, perhaps...) that if you go changing those parameters (eg:
> >> bumping up checkpoint_timeout to 30 minutes and max_wal_size up enough
> >> that you're still checkpointing based on time and not due to running out
> >> of WAL space) then you might need to consider raising the timeout for
> >> pg_ctl to wait around for the server to finish going through crash
> >> recovery due to all of the outstanding changes since the last
> >> checkpoint.
> >
> > It is important for users to be aware of this, but I don't think the
> > relationship between checkpoint_timeout and recovery time is linear, so
> > it's unclear what the exact advice should be.
>
> This is a right assumption for steady workloads with few DDLs, but for
> example once a couple of CREATE DATABASE records are in such a law is
> broken.

I don't expect CREATE DATABASE to be terribly frequent, and it doesn't
actually change the rule that the checkpoint_timeout is a maximum.

Thanks!

Stephen