Re: [HACKERS] Replication status in logical replication

On Fri, Jul 6, 2018 at 2:21 PM, Michael Paquier <michael@paquier.xyz> wrote:
> On Thu, Jul 05, 2018 at 05:13:27PM +0900, Michael Paquier wrote:
>> This concerns as well v10, so that's not actually an open item...
>> Well, it was an open item last year.  The last set of patches is from
>> Simon here:
>> https://www.postgresql.org/message-id/CANP8%2BjLwgsexwdPkBtkN5kdHN5TwV-d%3Di311Tq_FdOmzJ8QyRQ%40mail.gmail.com
>
> logical_repl_caught_up_v4alt2.patch is actually incorrect after I tested
> the thing, and that logical_repl_caught_up_v4.patch gets the correct
> call.
>
>> Simon, do you feel confident with your patch?  If yes, could you finish
>> wrapping it?  I am getting myself familiar with the problem as this has
>> been around for some time now so I am reviewing the thing as well and
>> then I can board the ship..
>
> Okay, I have spent some time today looking at this patch, and the error
> is very easy to reproduce once you do that in the TAP tests:
> 1) Stop and start once the publisher in one of the tests of
> src/test/subscription.
> 2) Enforce wait_for_catchup() to check for state = 'streaming'.
> And then you would see the tests waiting until timeout is reached and
> then die.
>
> I would be inclined to add those tests in the final patch, the
> disadvantage being that 1) makes one of the test scripts a bit longer,
> but it can reproduce the failures most of the time.  Having 2) is
> actually nice for physical replication as the tests in
> src/test/recovery/ use wait_for_catchup() in various ways.
>
> Some other notes about the patch:
> - I switched the error message in WalSndLoop as mentioned upthread for
> nodes catching up, aka no more "primary" but "upstream server".
> - Added a note about using only GetFlushRecPtr in XLogSendLogical as
> logical decoding cannot be used on standby nodes.  If one day logical
> decoding gets supports on standby then this would need an update as
> well.
>
> Does this look fine to all the folks involved in this thread?  It is
> Friday afternoon here so my brain is getting fried, but I can finish
> wrapping up this patch at the beginning of next week if there are no
> objections.  At quick glance this indeed would need a backpatch down to
> 9.4 but I have not spent time testing those configurations yet.

Thank you for updating the patch. The patch looks fine to me, and I
agree with all changes you made.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center