Hi,
On 9/25/23 6:10 AM, shveta malik wrote:
On Fri, Sep 22, 2023 at 3:48 PM Amit Kapila <amit.kapil...@gmail.com> wrote:
On Thu, Sep 21, 2023 at 9:16 AM shveta malik <shveta.ma...@gmail.com> wrote:
On Tue, Sep 19, 2023 at 10:29 AM shveta malik <shveta.ma...@gmail.com> wrote:
Currently in patch001, synchronize_slot_names is a GUC on both primary
and physical standby. This GUC tells which all logical slots need to
be synced on physical standbys from the primary. Ideally it should be
a GUC on physical standby alone and each physical standby should be
able to communicate the value to the primary (considering the value
may vary for different physical replicas of the same primary). The
primary on the other hand should be able to take UNION of these values
and let the logical walsenders (belonging to the slots in UNION
synchronize_slots_names) wait for physical standbys for confirmation
before sending those changes to logical subscribers. The intent is
logical subscribers should never be ahead of physical standbys.
Before getting into the details of 'synchronize_slot_names', I would
like to know whether we really need the second GUC
'standby_slot_names'. Can't we simply allow all the logical wal
senders corresponding to 'synchronize_slot_names' to wait for just the
physical standby(s) (physical slot corresponding to such physical
standby) that have sent ' synchronize_slot_names'list? We should have
one physical standby slot corresponding to one physical standby.
yes, with the new approach (to be implemented next) where we plan to
send synchronize_slot_names from each physical standby to primary, the
standby_slot_names GUC should no longer be needed on primary. The
physical standbys sending requests should automatically become the
ones to be waited for confirmation on the primary.
I think that standby_slot_names could be used to do some filtering (means
for which standby(s) we don't want the logical replication on the primary to go
ahead and for which standby(s) one would allow it).
I think that removing the GUC would:
- remove this flexibility
- probably open corner cases like: what if a standby is down? would that mean
that synchronize_slot_names not being send to the primary would allow the
decoding
on the primary to go ahead?
So, I'm not sure we should remove this GUC.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
