Re: Race condition in recovery?

At Mon, 7 Jun 2021 10:40:27 -0400, Robert Haas <robertmhaas(at)gmail(dot)com> wrote in
> On Mon, Jun 7, 2021 at 12:57 AM Kyotaro Horiguchi
> <horikyota(dot)ntt(at)gmail(dot)com> wrote:
> > Unfortunately no. The backslashes in the binary path need to be
> > escaped. (taken from PostgresNode.pm:1008)
> >
> > > (my $perlbin = $^X) =~ s{\\}{\\\\}g if ($TestLib::windows_os);
> > > $node_primary->append_conf(
> > > 'postgresql.conf', qq(
> > > archive_command = '$perlbin "$FindBin::RealBin/cp_history_files" "%p" "$archivedir_primary/%f"'
> > > ));
> >
> > This works for me.
>
> Hmm, OK. Do you think we also need to use perl2host in this case?

I understand that perl2host converts '/some/where' style path to the
native windows path 'X:/any/where' if needed. Since perl's $^X is
already in native style so I think we don't need to use it.

> > Ugh! Sorry. I meant "The explicit teardowns are useless". That's not
> > harmful but it is done by PostgresNode.pm automatically(implicitly)
> > and we don't do that in the existing scripts.
>
> OK. I don't think it's a big deal, but we can remove them.

Thanks.

> I went back and looked at your patch again, now that I understand the
> issue better. I believe it's not necessary to do this here, because
> StartupXLOG() already contains a check for the same thing:
>
> /*
> * If the location of the checkpoint record is not on the expected
> * timeline in the history of the requested timeline, we cannot proceed:
> * the backup is not part of the history of the requested timeline.
> */
> Assert(expectedTLEs); /* was initialized by reading checkpoint
> * record */
> if (tliOfPointInHistory(checkPointLoc, expectedTLEs) !=
> checkPoint.ThisTimeLineID)
> ...
>
> This code is always run after ReadCheckpointRecord() returns. And I
> think that your only concern here is about the case where the
> checkpoint record is being fetched, because otherwise expectedTLEs
> must already be set.

Sure. Thanks for confirming that, and agreed.

> By the way, I also noticed that your version of the patch contains a
> few words which are spelled incorrectly: hearafter, and incosistent.

Mmm. Sorry for them..

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center