Re: Optionally automatically disable logical replication subscriptions on error

On Mon, Jun 21, 2021 at 10:55 AM Mark Dilger
<mark(dot)dilger(at)enterprisedb(dot)com> wrote:
>
> > On Jun 20, 2021, at 10:11 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > However, I see a different case where there could be
> > multiple failing xids and that can happen during initial table sync
> > where multiple workers failed due to some error. I am not sure your
> > patch would be able to capture all such failed transactions because
> > you are recording this information in pg_subscription and not in
> > pg_subscription_rel.
>
> Right, I wasn't trying to capture everything, just enough to give the user a reasonable indication of what went wrong. My patch was designed around the idea that the user would need to figure out how to fix the subscriber side prior to re-enabling the subscription. As such, I wasn't bothered with trying to store everything, just enough to give the user a clue where to look.
>

Okay, but the clue will be pretty random because you might end up just
logging one out of several errors.

> I don't mind if you want to store more information, and maybe that needs to be stored somewhere else. Do you believe pg_subscription_rel is a suitable location?
>
It won't be sufficient to store information in either
pg_subscription_rel or pg_susbscription. I think if we want to store
the required information in a catalog then we need to define a new
catalog (pg_subscription_conflicts or something like that) with
information corresponding to each rel in subscription (srsubid oid
(Reference to subscription), srrelid oid (Reference to relation),
<columns for error_info>). OTOH, we can choose to send the error
information to stats collector which will then be available via stat
view and update system catalog to disable the subscription but there
will be a risk that we might send info of failed transaction to stats
collector but then fail to update system catalog to disable the
subscription.

--
With Regards,
Amit Kapila.