Re: Logical replication timeout problem

On Tue, Jan 31, 2023 at 5:12 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Tue, Jan 31, 2023 at 5:03 PM Ashutosh Bapat
> <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
> >
> > On Tue, Jan 31, 2023 at 4:58 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > > Thanks, the patch looks good to me. I have slightly adjusted one of
> > > the comments and ran pgindent. See attached. As mentioned in the
> > > commit message, we shouldn't backpatch this as this requires a new
> > > callback and moreover, users can increase the wal_sender_timeout and
> > > wal_receiver_timeout to avoid this problem. What do you think?
> >
> > The callback and the implementation is all in core. What's the risk
> > you see in backpatching it?
> >
>
> Because we are changing the exposed structure and which can break
> existing extensions using it.

Is that because we are adding the new member in the middle of the
structure? Shouldn't extensions provide new libraries with each
maintenance release of PG?

>
> > Customers can adjust the timeouts, but only after the receiver has
> > timed out a few times. Replication remains broekn till they notice it
> > and adjust timeouts. By that time WAL has piled up. It also takes a
> > few attempts to increase timeouts since the time taken by a
> > transaction to decode can not be estimated beforehand. All that makes
> > it worth back-patching if it's possible. We had a customer who piled
> > up GBs of WAL before realising that this is the problem. Their system
> > almost came to a halt due to that.
> >
>
> Which version are they using? If they are at >=14, using "streaming =
> on" for a subscription should also avoid this problem.

13.

--
Best Wishes,
Ashutosh Bapat