Re: PostgreSQL Failback without rebuild
Node A could get ahead even if it has been shut down cleanly BEFORE the promotion?
I'd always assumed if I shut down the master the slave would be at the same point after shutdown - is this incorrect?
Cheers,
James Sewell,
PostgreSQL Team Lead / Solutions Architect
______________________________________
On Fri, Feb 7, 2014 at 4:58 PM, Michael Paquier <michael.paquier@gmail.com> wrote:
On Fri, Feb 7, 2014 at 1:57 PM, James Sewell <james.sewell@lisasoft.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'):
- Stop Node A
- Promote Node B
- 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
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