Re: Updated backup APIs for non-exclusive backups

Stephen Frost wrote:
> > > On restore, you're
> > > going to need to create a recovery.conf (at least in released versions)
> > > which provides a restore command (needed even in HEAD today) to get the
> > > old WAL, so having to also create the backup_label file shouldn't be
> > > that difficult.
> >
> > You write "recovery.conf" upon recovery, when you have the restored
> > backup, so you have it on a file system.  No problem adding a file then.
> >
> > This is entirely different from adding a "backup_label" file to
> > a backup that has been taken by a backup software in some arbitrary
> > format in some arbitrary location (think snapshot).
>
> There isn’t any need to write the backup label before you restore the database,
> just as you write recovery.conf then.

Granted.
But it is pretty convenient, and writing it to the data directory right away
is a good thing on top, because it reduces the danger of inadvertedly
starting the backup without recovery.

> > > Lastly, if you really want, you can extract out the data from
> > > pg_stop_backup in whatever your post-backup script is.
> >
> > Come on, now.
> > You usually use backup techniques like that because you can't get
> > your large database backed up in the available time window otherwise.
>
> I’m not following what you’re trying to get at here, why can’t you extract
> the data for the backup label from pg_stop_backup..?  Certainly other tools
> do, even ones that do extremely fast parallel backups..  the two are
> completely independent.
>
> Did you think I meant pg_basebackup..?  I certaily didn’t.

Oh yes, I misunderstood.  Sorry.

Yes, you can come up with a post-backup script that somehow communicates
with your pre-backup script to get the information, but it sure is
inconvenient.  Simplicity is good in backup solutions, because complicated
things tend to break more easily.

> > I thought our goal is to provide convenient backup methods...
>
> Correctness would be first and having a broken system because of a crash during a backup isn’t correct.

"Not starting up without manual intervention" is not actually broken...