Re: Recovery Test Framework

On Mon, Jan 12, 2009 at 2:05 PM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> Well, I've been keeping an eye on both Hot Standby and Synchronous
> Replication patches. IMHO the Hot Standby patch is architecturally sound,
> and while I suggested some pretty big changes just recently (which Simon
> picked up and did already), it's in pretty good shape. No doubt there's
> still some issues that haven't been uncovered, comments to be fixed,
> documentation to be written, but no showstoppers or anything that requires a
> major rewrite. There's one todo item left: prepared transactions, but I
> don't think there's anything fundamentally hard about them, just needs to be
> fixed. Simon mentioned usability issues related to who/when queries get
> cancelled, but I think we've discussed that to death already and the patch
> handles it quite nicely.

Cool - that's good to hear.

> IMHO, the synchronous replication isn't in such good shape, I'm afraid. I've
> said this before, but I'm not happy with the "built from spare parts" nature
> of it. You shouldn't have to configure an archive, file-based log shipping
> using rsync or whatever, and pg_standby. All that is in addition to the
> direct connection between master and slave. The slave really should be able
> to just connect to the master, and download all the WAL it needs directly.
> That's a huge usability issue if left as is, but requires very large
> architectural changes to fix.

Yeah, I wasn't thinking about this, but you had mentioned it before,
and I thought (and think) it's a pretty fair criticism. I think the
base backup should be integrated into the mechanism as well. I want
to just be able to configure the master and slave for replication,
fire up the slave, and walk away. Without that, I agree that it's
likely to be too cumbersome for any actual use.

>> One thing I find interesting is that the "Infrastructure Changes for
>> Recovery" patch became the foundation for both "Hot Standby" and
>> "Synchronous Replication". That implies that those changes might be
>> of somewhat more general interest, at least as the foundation for
>> further work. If we HS and/or SR are out of reach, it might be worth
>> at least looking to see if any of that infrastructure work can be
>> reasonably be committed for 8.4.
>
> Yeah, being able to do an online checkpoint after recovery has some value of
> its own.

Is there anything standing in the way of committing that patch? I
don't think I've seen anything mentioned on -hackers.

...Robert