Re: BUG #17577: pg_ctl promote is not preemptive in archive recovery

At Fri, 5 Aug 2022 13:01:19 -0700, Daniel Farina <daniel(at)fdr(dot)io> wrote in
> On Fri, Aug 5, 2022 at 12:21 PM David G. Johnston
> <david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
> > On what basis are you considering this a bug? Or, IOW, what do you expect to happen? It doesn't seem possible for the promotion to actually happen as the server knows additional WAL must exist that it hasn't yet restored since all attempts to restore WAL have succeeded.
>
> pg_ctl promote should have consistent behavior regardless of WAL
> transport. If I (or a computer program of mine) is issuing pg_ctl
> promote, I mean for it to happen now, that's how it happens with
> streaming, and in the case of streaming, the amount of WAL that can
> eventually come into existence is practically unbounded.

pg_ctl just commands or prompts server to do that. The server
responds to the commands at its convenience. It works the same way
for start/stop/restart and maybe some other subcommands. If
something's going wrong on the server, there's cases it cannot fulfill
the order. For example, regarding to streaming, if walreceiver
process is hanging for some reason, pg_ctl promote waits for the
server to promote but eventually will time out while the server cannot
promote.

This is that kind of behavior by design, which is not a bug. Of
course, we're open for someone coming up with a good improvement of
those behviors.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center