Re: Remove Deprecated Exclusive Backup Mode

On Thu, Feb 28, 2019 at 05:08:24PM +0200, David Steele wrote:
> On 2/28/19 4:44 PM, Fujii Masao wrote:
> > On Wed, Feb 27, 2019 at 4:35 PM Laurenz Albe <laurenz.albe@cybertec.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.
> 
> It is problematic because we have a message encouraging users to delete
> backup_label when in fact they should be creating recovery.signal.

Should we issue a client NOTICE/WARNING message as part of
pg_start_backup to indicate what to do if the server crashes before
pg_stop_backup()?

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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