Re: Remove Deprecated Exclusive Backup Mode

On Wed, Jul 1, 2020 at 9:59 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> On Wed, Jul 1, 2020 at 3:50 PM Magnus Hagander <magnus(at)hagander(dot)net>
> wrote:
> > As far as I've seen, the one thing that people have problems with in the
> exclusive mode backups are precisely the fact that they have to keep a
> persistent conneciton open, and thus it cannot work together with backup
> software that is limited to only supporting running a pre- and a post
> script.
> >
> > Something like I have suggested here is to solve *that* problem. I don't
> think anybody actually explicitly wants "exclusive backups" -- they want a
> backup solution that plugs into their world of pre/post scripts. And if we
> can make that one work in a safer way than the current exclusive backups,
> ohw is that not an improvement?
>
> Yeah, I guess that's a pretty fair point. I have to confess to having
> somewhat limited enthusiasm for adding a third mode here, but it might
> be worth it.
>

The intention is definitely not to have 3 modes. If we build this mode the
intention is that it is strictly better than exclusive mode, and thus
exclusive mode can finally be removed. (Whereas the nonexclusive mode is
better in many ways, but not all)

It seems pretty well inevitable to me that people are going to forget
> to end them. I am not sure exactly what the consequences of that will
> be, but if for example there's a limited number of shared memory slots
> to store information about these backups, then if you leak any, you'll
> eventually run out of slots and your backups will start failing. I
> feel like that's a going to happen to about 75% of the people who try
> to use this new backup mode at some point in time, but maybe I'm a
> pessimist.[1]
>

Agreed. yet this is still strictly better or equal than the current
exclusive backups, which fail after forgetting that *once*.

If we could jigger things so that you don't need to stop the backup at
> all, you only start it, and whether you ever finish copying everything
> is something about which the system need not know or care, that would
> be a lot nicer. I'm not sure I see how to do that, though.
>
>
Yeah, I'm not sure about that one either.

//Magnus