Re: could not stat promote trigger file leads to shutdown

On Fri, Nov 15, 2019 at 10:49 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Thu, Nov 14, 2019 at 10:38:30AM -0500, Tom Lane wrote:
> > It is harsh, but I suspect if we just logged the complaint, we'd get
> > bug reports about "Postgres isn't reacting to my trigger file",
> > because people don't read the postmaster log unless forced to.
> > Is there some more-visible way to report the problem, short of
> > shutting down?
> >
> > (BTW, from this perspective, WARNING is especially bad because it
> > might not get logged at all. Better to use LOG.)
>
> Neither am I comfortable with that.

I always wonder why WARNING was defined that way.
I think that users usually pay attention to the word "WARNING"
rather than "LOG".

> > One thought is to try to detect the misconfiguration at postmaster
> > start --- better to fail at startup than sometime later. But I'm
> > not sure how reliably we could do that.
>
> I think that we could do something close to the area where
> RemovePromoteSignalFiles() gets called. Why not simply checking the
> path defined by PromoteTriggerFile() at startup time then? I take it
> that the only thing we should not complain about is stat() returning
> ENOENT when looking at the promote file defined.

promote_trigger_file is declared as PGC_SIGHUP,
so such check would be necessary even while the standby is running.
Which can cause the server to fail after the startup.

Regards,

--
Fujii Masao