Re: Add recovery to pg_control and remove backup_label

On Sun, Nov 26, 2023 at 3:42 AM Stephen Frost <sfrost@snowman.net> wrote:
> What would really be helpful would be hearing from these individuals
> directly as to what the issues are with the changes, such that perhaps
> we can do things better in the future to avoid whatever the issue is
> they're having with the changes.  Simply saying we shouldn't make
> changes in this area isn't workable and the constant push-back is
> actively discouraging to folks trying to make improvements.  Obviously
> it's a biased view, but we've not had issues making the necessary
> adjustments in pgbackrest with each release and I feel like if the
> authors of wal-g or barman did that they would have spoken up.

I'm happy if people show up to comment on proposed changes, but I
think you're being a little bit unrealistic here. I have had to help
plenty of people who have screwed up their backups in one way or
another, generally by using some home-grown script, sometimes by
misusing some existing backup tool. Those people are EDB customers;
they don't read and participate in discussions here. If they did,
perhaps they wouldn't be paying EDB to have me and my colleagues sort
things out for them when it all goes wrong. I'm not trying to say that
EDB doesn't have customers who participate in mailing list
discussions, because we do, but it's a small minority, and I don't
think that should surprise anyone. Moreover, the people who don't
wouldn't necessarily have the background, expertise, or *time* to
assess specific proposals in detail. If your point is that my
perspective on what's helpful or unhelpful is not valid because I've
only helped 30 people who had problems in this area, but that the
perspective of those 30 people who were helped would be more valid,
well, I don't agree with that. I think your perspective and David's
are valid precisely *because* you've worked a lot on pgbackrest and no
doubt interacted with lots of users; I think Andres's perspective is
valid precisely *because* of his experience working with the fleet at
Microsoft and individual customers at EDB and 2Q before that; and I
think my perspective is valid for the same kinds of reasons.

I am more in agreement with the idea that it would be nice to hear
from backup tool authors, but I think even that has limited value.
Surely we can all agree that if the backup tool is correctly written,
none of this matters, because you'll make the tool do the right things
and then you'll be fine. The difficulty here, and the motivation
behind this proposal and others like it, is that too many users fail
to follow the procedure correctly. If we hear from the authors of
well-written backup tools, I expect they will tell us they can adapt
their tool to whatever we do. And if we hear from the authors of
poorly-written tools, well, I don't think their opinions would form a
great basis for making decisions.

> [ lengthy discussion of tools that don't work any more ]

What confuses me here is that you seem to be arguing that we should
*once again* make a breaking change to the backup API, but at the same
time you're acknowledging that there are plenty of tools out there on
the Internet that have gotten broken by previous rounds of changes.
It's only one step from there to conclude that whacking the API around
does more harm than good, but you seem to reject that conclusion.

Personally, I haven't yet seen any evidence that the removal of
exclusive backup mode made any real difference one way or the other. I
think I've heard about people needing to adjust code for it, but not
about that being a problem. I have yet to run into anyone who was
previously using it but, because it was deprecated, switched to doing
something better and safer. Have you?

--
Robert Haas
EDB: http://www.enterprisedb.com