Re: Synchronizing slots from primary to standby

Hi,

On Fri, Feb 23, 2024 at 09:46:00AM +0000, Zhijie Hou (Fujitsu) wrote:
> On Friday, February 23, 2024 1:22 PM shveta malik <shveta.malik@gmail.com> wrote:
> 
> > 
> > Thanks for the patches. Had a quick look at v95_2, here are some
> > trivial comments:
> 
> Thanks for the comments.
> 
> > 6) streaming replication standby server slot names that logical walsender
> > processes will wait for
> > 
> > Is it better to say it like this? (I leave this to your preference)
> > 
> > streaming replication standby server slot names for which logical
> > walsender processes will wait.
> 
> I feel the current one seems better, so didn’t change. Other comments have been
> addressed. Here is the V97 patch set which addressed Shveta's comments.
> 
> 
> Besides, I'd like to clarify and discuss the behavior of standby_slot_names once.
> 
> As it stands in the patch, If the slots specified in standby_slot_names are
> dropped or invalidated, the logical walsender will issue a WARNING and continue
> to replicate the changes. Another option for this could be to have the
> walsender pause until the slot in standby_slot_names is re-created or becomes
> valid again. Does anyone else have an opinion on this matter ?

Good point, I'd vote for: the only reasons not to wait are:

- slots mentioned in standby_slot_names exist and valid and do catch up
or
- standby_slot_names is empty

The reason is that setting standby_slot_names to a non empty value means that
one wants the walsender to wait until the standby catchup. The way to remove this
intentional behavior should be by changing the standby_slot_names value (not the
existence or the state of the slot(s) it points too).

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com