Re: Reducing pg_ctl's reaction time

On Tue, Jun 27, 2017 at 11:59 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> I wrote:
> > Andres Freund <andres(at)anarazel(dot)de> writes:
> >> On 2017-06-26 17:38:03 -0400, Tom Lane wrote:
> >>> Hm. Take that a bit further, and we could drop the connection probes
> >>> altogether --- just put the whole responsibility on the postmaster to
> >>> show in the pidfile whether it's ready for connections or not.
>
> >> Yea, that seems quite appealing, both from an architectural, simplicity,
> >> and log noise perspective. I wonder if there's some added reliability by
> >> the connection probe though? Essentially wondering if it'd be worthwhile
> >> to keep a single connection test at the end. I'm somewhat disinclined
> >> though.
>
> > I agree --- part of the appeal of this idea is that there could be a net
> > subtraction of code from pg_ctl. (I think it wouldn't have to link libpq
> > anymore at all, though maybe I forgot something.) And you get rid of a
> > bunch of can't-connect failure modes, eg kernel packet filter in the way,
> > which probably outweighs any hypothetical reliability gain from
> confirming
> > the postmaster state the old way.
>
> Here's a draft patch for that. I quite like the results --- this seems
> way simpler and more reliable than what pg_ctl has done up to now.
> However, it's certainly arguable that this is too much change for an
> optional post-beta patch.

In the now-committed version of this, the 'pg_ctl start' returns
successfully as soon as the server reaches a consistent state. Which is OK,
except that it does the same thing when hot_standby=off. When
hot_standby=off, I would expect it to wait for the end of recovery before
exiting with a success code.

Cheers,

Jeff