Re: 'replication checkpoint has wrong magic' on the newly cloned replicas

Greetings,

On Wed, Nov 29, 2017 at 12:41 Oleksii Kliukin <oleksii(at)fastmail(dot)com> wrote:

> Hi Stephen,
>
> > On 29. Nov 2017, at 15:54, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> >
> > Greetings,
> >
> > * Alex Kliukin (alexk(at)hintbits(dot)com) wrote:
> >> The cloning itself is done by copying a compressed image via ssh,
> >> running the
> >> following command from the replica:
> >>
> >> """ssh {master} 'cd {master_datadir} && tar -lcp --exclude "*.conf" \
> >> --exclude "recovery.done" \
> >> --exclude "pacemaker_instanz" \
> >> --exclude "dont_start" \
> >> --exclude "pg_log" \
> >> --exclude "pg_xlog" \
> >> --exclude "postmaster.pid" \
> >> --exclude "recovery.done" \
> >> * | pigz -1 -p 4' | pigz -d -p 4 | tar -xpmUv -C
> >> {slave_datadir}""
> >>
> >> The WAL archiving starts before the copy starts, as the script that
> >> clones the
> >> replica checks that the WALs archiving is running before the cloning.
> >
> > Maybe you've doing it and haven't mentioned it, but you have to use
> > pg_start/stop_backup
>
> Sorry for not mentioning it, as it seemed obvious, but we are calling
> pg_start_backup and pg_stop_backup at the right time.

Ah, not something I can assume, heh.

Then it depends on which version of PG and if you’re able to run start/stop
on the replica or not. If you can’t run it on the replica and have to run
it on the primary (prior to 9.6) then you need to make sure to wait for
things to happen on the primary and for that to be replicated before you
can start.

If you’re on 9.6 and using non-exclusive backup, you need to be sure to
capture the contents of the stop backup and write it into backup_label
before you start the system back up.

This is off the top of my head, so be sure to go double check the docs, of
course.

Thanks!

Stephen