RE: Time delayed LR (WAS Re: logical replication restrictions)

Hi,

On Friday, January 20, 2023 6:13 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> On Fri, Jan 20, 2023 at 2:23 PM shveta malik <shveta(dot)malik(at)gmail(dot)com> wrote:
> >
> > On Fri, Jan 20, 2023 at 1:08 PM Peter Smith <smithpb2250(at)gmail(dot)com>
> wrote:
> >
> > > a) the message should say that this is the *remaining* time to left to wait.
> > >
> > > b) it might be convenient to know from the log what was the original
> > > min_apply_delay value in the 1st place.
> > >
> > > For example, the logs might look something like this:
> > >
> > > DEBUG: time-delayed replication for txid 1234, min_apply_delay =
> > > 160000 ms. Remaining wait time: 159972 ms
> > > DEBUG: time-delayed replication for txid 1234, min_apply_delay =
> > > 160000 ms. Remaining wait time: 142828 ms
> > > DEBUG: time-delayed replication for txid 1234, min_apply_delay =
> > > 160000 ms. Remaining wait time: 129994 ms
> > > DEBUG: time-delayed replication for txid 1234, min_apply_delay =
> > > 160000 ms. Remaining wait time: 110001 ms ...
> > >
> >
> > +1
> > This will also help when min_apply_delay is set to a new value in
> > between the current wait. Lets say, I started with min_apply_delay=5
> > min, when the worker was half way through this, I changed
> > min_apply_delay to 3 min or say 10min, I see the impact of that change
> > i.e. new wait-time is adjusted, but log becomes confusing. So, please
> > keep this scenario as well in mind while improving logging.
> >
>
>
> when we send-feedback during apply-delay after every
> wal_receiver_status_interval , the log comes as:
> 023-01-19 17:12:56.000 IST [404795] DEBUG: sending feedback (force 1) to
> recv 0/1570840, write 0/1570840, flush 0/1570840
>
> Shall we have some info here to indicate that it is sent while waiting for
> apply_delay to distinguish it from other such send-feedback logs?
> It will
> make apply_delay flow clear in logs.
This additional tip of log information has been added in the latest v18.
Kindly have a look at it in [1].

[1] - https://www.postgresql.org/message-id/TYCPR01MB8373BED9E390C4839AF56685EDC59%40TYCPR01MB8373.jpnprd01.prod.outlook.com

Best Regards,
Takamichi Osumi