Re: [bug fix] Cascading standby cannot catch up and get stuck emitting the same message repeatedly

From: pgsql-hackers-owner(at)postgresql(dot)org
> [mailto:pgsql-hackers-owner(at)postgresql(dot)org] On Behalf Of Tsunakawa,
> Our customer hit a problem of cascading replication, and we found the cause.
> They are using the latest PostgreSQL 9.2.18. The bug seems to have been
> fixed in 9.4 and higher during the big modification of xlog.c, but it's
> not reflected in older releases.
>
> The attached patch is for 9.2.18. This just borrows the idea from 9.4 and
> higher.
>
> But we haven't been able to reproduce the problem. Could you review the
> patch and help to test it? I would very much appreciate it if you could
> figure out how to reproduce the problem easily.

We could successfully reproduce the problem and confirm that the patch fixes it. Please use the attached script to reproduce the problem. Place it in an empty directory and just run "./test.sh" with no argument. It creates three database clusters (primary, standby, and cascading standby) in the current directory.

Could you review the patch and commit it for the next release? If you think I should register the patch with the CommitFest even if the problem occurs in 9.2 and 9.3, please say so. I'll do so if there's no comment.

Regards
Takayuki Tsunakawa