RE: Exit walsender before confirming remote flush in logical replication

> Dear Andres, Amit,
>
> > On 2023-02-07 09:00:13 +0530, Amit Kapila wrote:
> > > On Tue, Feb 7, 2023 at 2:04 AM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > > > How about we make it an option in START_REPLICATION? Delayed logical
> > rep can
> > > > toggle that on by default.
> >
> > > Works for me. So, when this option is set in START_REPLICATION
> > > message, walsender will set some flag and allow itself to exit at
> > > shutdown without waiting for WAL to be sent?
> >
> > Yes. I think that might be useful in other situations as well, but we don't
> > need to make those configurable initially. But I imagine it'd be useful to set
> > things up so that non-HA physical replicas don't delay shutdown, particularly
> > if they're geographically far away.
>
> Based on the discussion, I made a patch for adding a walsender option
> exit_before_confirming to the START_STREAMING replication command. It can
> be
> used for both physical and logical replication. I made the patch with
> extendibility - it allows adding further options.
> And better naming are very welcome.
>
> For physical replication, the grammar was slightly changed like a logical one.
> It can now accept options but currently, only one option is allowed. And it is
> not used in normal streaming replication. For logical replication, the option is
> combined with options for the output plugin. Of course, we can modify the API to
> better style.
>
> 0001 patch was ported from time-delayed logical replication thread[1], which
> uses
> the added option. When the min_apply_delay option is specified and publisher
> seems
> to be PG16 or later, the apply worker sends a START_REPLICATION query with
> exit_before_confirming = true. And the worker will reboot and send
> START_REPLICATION
> again when min_apply_delay is changed from zero to a non-zero value or non-zero
> to zero.
>
> Note that I removed version number because the approach is completely changed.
>
> [1]:
> https://www.postgresql.org/message-id/TYCPR01MB8373BA483A6D2C924C60
> 0968EDDB9(at)TYCPR01MB8373(dot)jpnprd01(dot)prod(dot)outlook(dot)com

I noticed that previous ones are rejected by cfbot, even if they passed on my environment...
PSA fixed version.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED