Re: Invalid data read from synchronously replicated hot standby

Sameer Kumar <sameer(dot)kumar(at)ashnik(dot)com> wrote on 04/21/2016 13:56:52:

> From: Sameer Kumar <sameer(dot)kumar(at)ashnik(dot)com>
> To: Martin Kamp Jensen/DK/Schneider(at)Europe, pgsql-general(at)postgresql(dot)org
> Date: 04/21/2016 14:00
> Subject: Re: [GENERAL] Invalid data read from synchronously
> replicated hot standby
>
>

> On Thu, 21 Apr 2016 04:05 , <martin(dot)kamp(dot)jensen(at)schneider-electric(dot)com>
wrote:
> Hi,
>
> We are getting invalid data when reading from a synchronously
> replicated hot standby node in a 2-node setup. To better understand
> the situation, we have created a document that provides an overview.
> We are hoping that someone might be able to confirm whether or not
> the setup makes sense, i.e., whether we are using PostgreSQL
> correctly and experiencing a bug, or if we are using PostgreSQL
incorrectly.
>
> Link to document that contains a step-by-step description of the
situation:
> https://docs.google.com/document/d/1MuX8rq1gKw_WZ-
> HVflqxFslvXNTRGKa77A4NHto4ue0/edit?usp=sharing
>
>
>
>
>
> If the setup is sane (and expected to work), we will work on setting
> up a minimal reproduce that avoids our complete system. We are
> thinking that a scripted Ansible/Vagrant setup makes sense.
>
> I am not sure if it is because of that but you are on an old patch.
> Upgrade to latest (I guess 9.1.21).

I have reproduced the issue on 9.1.20 which is the latest version for
Debian 6 (yes, I know, old stuff).

In the mean time, we are preparing a new platform on 9.5.2 where I have
not been able to reproduce the issue (however, we have introduced a lot of
changes besides upgrading PostgreSQL). I would have liked to be able to
come up with a minimal reproduce to be able to reason about the issue but
I guess we will not pursue that for now.

>
> Once you have upgraded, re-create the stand by from scratch using a
> basebackup and then see if the error is still there.
>
>
> Best regards,
> Martin
> --
> --
> Best Regards
> Sameer Kumar | DB Solution Architect
> ASHNIK PTE. LTD.
> 101 Cecil Street, #11-11 Tong Eng Building, Singapore 069 533
> T: +65 6438 3504 | M: +65 8110 0350 | www.ashnik.com
>
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