Re: Remove Deprecated Exclusive Backup Mode

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, David Steele <david(at)pgmasters(dot)net>, Adrien NAYRAT <adrien(dot)nayrat(at)anayrat(dot)info>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Remove Deprecated Exclusive Backup Mode
Date: 2019-02-28 14:53:10
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* Fujii Masao (masao(dot)fujii(at)gmail(dot)com) wrote:
> On Wed, Feb 27, 2019 at 4:35 PM Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:
> >
> > Fujii Masao wrote:
> > > So, let me clarify the situations;
> > >
> > > (3) If backup_label.pending exists but recovery.signal doesn't, the server
> > > ignores (or removes) backup_label.pending and do the recovery
> > > starting the pg_control's REDO location. This case can happen if
> > > the server crashes while an exclusive backup is in progress.
> > > So crash-in-the-middle-of-backup doesn't prevent the recovery from
> > > starting in this idea
> >
> > That's where I see the problem with your idea.
> >
> > It is fairly easy for someone to restore a backup and then just start
> > the server without first creating "recovery.signal", and that would
> > lead to data corruption.
> Isn't this case problematic even when a backup was taken by pg_basebackup?
> Because of lack of recovery.signal, no archived WAL files are replayed and
> the database may not reach to the latest point.

There's a number of problems, imv, that I think have just been
ignored/missed when it comes to the recovery.conf removal and tools like
pg_basebackup, see this msg also:

At this point, I think we need to put these issues on the v12 open items
page so that we don't forget about them and get these things fixed
before v12 comes out.



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