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
______________________________________

Level 2, 50 Queen St, Melbourne VIC 3000

*P *(+61) 3 8370 8000 *W* www.lisasoft.com *F *(+61) 3 8370 8099

On Fri, Feb 7, 2014 at 4:58 PM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com>wrote:

>
>
>
> 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
>

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