Re: Updated backup APIs for non-exclusive backups

On Mon, Nov 26, 2018 at 6:44 AM Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
wrote:

> On Sun, 2018-11-25 at 22:01 +0100, Magnus Hagander wrote:
> [about managing backups from pre- and post-file-system-backup scrips]
> > I agree with your point that it's not an uncommon thing to need. If a
> good solution
> > for it can be proposed that requires the exclusive backup interface,
> then I wouldn't
> > be against un-deprecating that. But that's going to require a lot more
> than just a
> > documentation change, IMHO. What could perhaps be handled with a
> documentation change,
> > however, is to document a good way for this type of setup to use the new
> interfaces.
>
> Good point, and it puts the ball in my court :^)
>

Enjoy :)

> > > I'm arguing on behalf of users that run a few databases, want a simple
> backup
> > > solution and are ready to deal with the shortcomings.
> >
> > Those that want a simple backup solution have one -- pg_basebackup.
> >
> > The exclusive backup API is *not* simple. It is convenient, but it is
> not simple.
> >
> > Actually having a simple API that worked with the pre/post backup
> scripts, that
> > would be an improvement that we should definitely want!
>
> Right; unfortunately it is not simple to come up with one that doesn't
> exhibit
> the problems of the existing exclusive backup.
>

Right, it turns out to actually be a hard problem. The old API pretended it
wasn't, which wasn't really very helpful in the long run...

Perhaps it's theoretically impossible. The goal is to disambiguate what a
> file
> system backup sees in backup mode and what the startup process sees after
> a crash
> in backup mode, and I can't see how that could be done.
>

Not if it's in the same physical location, no, I think that's really hard.

--
Magnus Hagander
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>