Horton

Re: Race condition in recovery?

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-05-24T05:04:36Z
Lists: pgsql-hackers 
On Mon, May 24, 2021 at 10:17 AM Kyotaro Horiguchi
<horikyota.ntt@gmail.com> wrote:
>
> At Sun, 23 May 2021 21:37:58 +0530, Dilip Kumar <dilipbalaut@gmail.com> wrote in
> > On Sun, May 23, 2021 at 2:19 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> > >
> > > On Sat, May 22, 2021 at 8:33 PM Robert Haas <robertmhaas@gmail.com> wrote:
> >
> > I have created a tap test based on Robert's test.sh script.  It
> > reproduces the issue.  I am new with perl so this still needs some
> > cleanup/improvement, but at least it shows the idea.
>
> I'm not sure I'm following the discussion here, however, if we were
> trying to reproduce Dilip's case using base backup, we would need such
> a broken archive command if using pg_basebackup witn -Xnone.  Becuase
> the current version of pg_basebackup waits for all required WAL
> segments to be archived when connecting to a standby with -Xnone.

Right, that's the reason if you see my patch I have dynamically
generated such archive command which skips everything other than the
history file
see below snippet from my patch, where I am generating a skip_cp
command and then I am using that as an archive command.

==
+# Prepare a alternative archive command to skip WAL files
+my $script = "#!/usr/bin/perl \n
+use File::Copy; \n
+my (\$source, \$target) = \@ARGV; \n
+if (\$source =~ /history/) \n
+{ \n
+ copy(\$source, \$target); \n
+}";
+
+open my $fh, '>', "skip_cp";
+print {$fh} $script;
===

  I
> don't bother reconfirming the version that fix took place, but just
> using -X stream instead of "none" we successfully miss the first
> segment of the new timeline in the upstream archive, though we need to
> erase pg_wal in the backup.  Either the broken archive command or
> erasing pg_wal of the cascade is required to the behavior to occur.
>
> The attached is how it looks like.

I will test this and let you know.  Thanks!

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Further refinement of stuck_on_old_timeline recovery test

  2. Adjust new test case to set wal_keep_segments.

  3. Adjust new test case to set wal_keep_size.

  4. Fix corner case failure of new standby to follow new primary.

  5. Back-port a few PostgresNode.pm methods.

  6. Allow PostgresNode.pm's backup method to accept backup_options.

  7. Add end-to-end testing of pg_basebackup's tar-format output.

  8. Allow PostgresNode.pm tests to wait for catchup

  9. Delay reading timeline history file until it's fetched from master.