Re: State of pg_createsubscriber

On Sun, May 19, 2024 at 11:20 PM Euler Taveira <euler(at)eulerto(dot)com> wrote:
>
> On Sun, May 19, 2024, at 2:30 PM, Tom Lane wrote:
>
> I'm fairly disturbed about the readiness of pg_createsubscriber.
> The 040_pg_createsubscriber.pl TAP test is moderately unstable
> in the buildfarm [1], and there are various unaddressed complaints
> at the end of the patch thread (pretty much everything below [2]).
> I guess this is good enough to start beta with, but it's far from
> being good enough to ship, IMO. If there were active work going
> on to fix these things, I'd feel better, but neither the C code
> nor the test script have been touched since 1 April.
>
>
> My bad. :( I'll post patches soon to address all of the points.
>

Just to summarize, apart from BF failures for which we had some
discussion, I could recall the following open points:

1. After promotion, the pre-existing replication objects should be
removed (either optionally or always), otherwise, it can lead to a new
subscriber not being able to restart or getting some unwarranted data.
[1][2].

2. Retaining synced slots on new subscribers can lead to unnecessary
WAL retention and dead rows [3].

3. We need to consider whether some of the messages displayed in
--dry-run mode are useful or not [4].

[1] - https://www.postgresql.org/message-id/CAA4eK1L6HOhT1qifTyuestXkPpkRwY9bOqFd4wydKsN6C3hePA%40mail.gmail.com
[2] - https://www.postgresql.org/message-id/flat/3fa9ef0f-b277-4c13-850a-8ccc04de1406%40eisentraut.org#152dacecfc8f0cf08cbd8ecb79d6d38f
[3] - https://www.postgresql.org/message-id/CAA4eK1KdCb%2B5sjYu6qCMXXdCX1y_ihr8kFzMozq0%3DP%3DauYxgog%40mail.gmail.com
[4] - https://www.postgresql.org/message-id/flat/3fa9ef0f-b277-4c13-850a-8ccc04de1406%40eisentraut.org#152dacecfc8f0cf08cbd8ecb79d6d38f

--
With Regards,
Amit Kapila.