RE: Synchronizing slots from primary to standby

On Thursday, February 29, 2024 7:36 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
>
> On Thu, Feb 29, 2024 at 7:04 AM Zhijie Hou (Fujitsu) <houzj(dot)fnst(at)fujitsu(dot)com>
> wrote:
> >
> > Here is the v101 patch set which addressed above comments.
> >
>
> Thanks for the patch. Few comments:
>
> 1) Shall we mention in doc that shutdown will wait for standbys in
> standby_slot_names to confirm receiving WAL:
>
> Suggestion for logicaldecoding.sgml:
>
> When <varname>standby_slot_names</varname> is utilized, the primary
> server will not completely shut down until the corresponding standbys,
> associated with the physical replication slots specified in
> <varname>standby_slot_names</varname>, have confirmed receiving the
> WAL up to the latest flushed position on the primary server.
>
> slot.c
> 2)
> /*
> * If a logical slot name is provided in standby_slot_names, report
> * a message and skip it. Although logical slots are disallowed in
> * the GUC check_hook(validate_standby_slots), it is still
> * possible for a user to drop an existing physical slot and
> * recreate a logical slot with the same name.
> */
>
> This is not completely true, we can still specify a logical slot during instance
> start and it will accept it.
>
> Suggestion:
> /*
> * If a logical slot name is provided in standby_slot_names, report
> * a message and skip it. It is possible for user to specify a
> * logical slot name in standby_slot_names just before the server
> * startup. The GUC check_hook(validate_standby_slots) can not
> * validate such a slot during startup as the ReplicationSlotCtl
> * shared memory is not initialized by that time. It is also
> * possible for user to drop an existing physical slot and
> * recreate a logical slot with the same name.
> */
>
> 3. Wait for physical standby to confirm receiving the given lsn
>
> standby -->standbys
>
>
> 4.
> In StandbyConfirmedFlush(), is it better to have below errdetail in all
> problematic cases:
> Logical replication is waiting on the standby associated with \"%s\
>
> We have it only for inactive pid case but we are waiting in all cases.

Thanks for the comments, I have addressed them.

Best Regards,
Hou zj