Re: PostgreSQL Failback without rebuild

On Fri, Feb 7, 2014 at 1:57 PM, James Sewell <james(dot)sewell(at)lisasoft(dot)com>wrote:

> I've just noticed that on PostgreSQL 9.3 I can do the following with a
> master node A and a slave node B (as long as I have set
> recovery_target_timeline = 'latest'):
>
> 1. Stop Node A
> 2. Promote Node B
> 3. Attach Node A as slave
>
> This is sufficient for my needs (I know it doesn't cover a crash), can
> anyone see any potential problems with this approach?
>
Yes, node A could get ahead of the point where WAL forked when promoting B.
In this case you cannot reconnect A to B, and need to actually recreate a
node from a fresh base backup, or rewind it. pg_rewind targets the latter,
postgres core is able to to the former, and depending on things like your
environment and/or the size of your server, you might prefer one or the
other.
Regards,
--
Michael