RE: Synchronizing slots from primary to standby

On Friday, December 15, 2023 1:32 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
>
> TODO:
> --Address the test comments in [1] for 050_standby_failover_slots_sync.pl
> --Review the feasibility of addressing one pending comment (comment 13 in
> [5]) of 'r'->'n' conversion.

Here is the V49 patch set which addressed above TODO items.

The patch also includes the following changes:

V49-0001

1) added some documents to mention it's user responsibility to ensure the table
sync is completed before subscriber to the new primary.
2) fix one CFbot failure in 050_standby_failover_slots_sync.pl.

V49-0002
1) added few comments to mention why we retain the READY state after promotion.
2) Prevent user from altering the slots that is being synced.
3) fix one CFbot failure in 050_standby_failover_slots_sync.pl.
4) Improve the 050_standby_failover_slots_sync.pl to remove some unnecessary
operations.

V49-0003

There is one unstable test in V48-0002 which is to validate the restart_lsn of
synced slot. We test it by checking "'$primary_restart_lsn' <= restart_lsn"
which would wrongly allow the standby to go ahead of primary. And it may fail
randomly as standby may still be lagging behind primary if the slot-sync worker
has gone to longer nap (10 sec) and has not taken the slots-changes yet. And
we cannot put sleep of 10sec here.

We may consider removing this test as it may be enough to test
that logical replication is proceeding well from the synced slots on new
primary. So, I temporarily move it into a separately patch for review.

Thanks Ajin for working on the testcases improvement.

>
> [1]:
> https://www.postgresql.org/message-id/CAHut%2BPtOc7J_n24HJ6f_dFWTu
> D3X2ApOByQzZf6jZz%2B0wb-ebQ%40mail.gmail.com
> [5]:
> https://www.postgresql.org/message-id/CAJpy0uDcOf5Hvk_CdCCAbfx9SY%
> 2Bog%3D%3D%3DtgiuhWKzkYyqebui9g%40mail.gmail.com

Best Regards,
Hou zj