Re: Use pg_rewind when target timeline was switched

On Tue, Sep 8, 2015 at 10:28 AM, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
wrote:

> On Tue, Sep 8, 2015 at 1:14 AM, Alexander Korotkov wrote:
> > On Thu, Aug 20, 2015 at 9:57 AM, Michael Paquier wrote:
> >> The code above looks correct to me when scanning the WAL history onwards
> >> though, which is what is done when extracting the page map, but not
> >> backwards when we try to find the last common checkpoint record. This
> code
> >> actually fails trying to open 2/0/2 that does not exist in the promoted
> >> standby's pg_xlog in my test case.
> >>
> >> Attached is a small script I have used to reproduce the failure.
> >
> >
> > Right, thanks! It should be fixed in the attached version of patch.
>
> So, instead of a code review, I have been torturing your patch and did
> advanced tests on it with the attached script, that creates a cluster
> as follows:
> master (5432)
> / \
> 1 (5433) 2 (5434)
> |
> 3 (5435)
> Once cluster is created, nodes are promoted in a certain order giving
> them different timeline jump properties:
> - master, stays on tli 1
> - standby 1, tli 1->2
> - standby 2, tli 1->3
> - standby 3, tli 1->2->4
> And data is inserted on each of them to make WAL fork properly.
> Finally the script tries to rewind one node using another node as
> source, and then tries to link this target node back to the source
> node via streaming replication.
>
> I have tested all the one-one permutations possible in the structure
> above (see commented portions at the bottom of my script), and all of
> them worked. I have to say that from the testing prospective this
> patch looks in great shape, and will greatly improve the use cases of
> pg_rewind!
>

Great! Many thanks for your testing!

I am planning to do as well a detailed code review rather soon.
>

Good, thanks.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company