Re: Use pg_rewind when target timeline was switched

On Sat, Sep 19, 2015 at 8:27 AM, Michael Paquier wrote:
> On Fri, Sep 18, 2015 at 6:25 PM, Michael Paquier wrote:
>> The refactoring of getTimelineHistory as you propose looks like a good
>> idea to me, I tried to remove by myself the difference between source
>> and target in copy_fetch.c and friends but this gets uglier,
>> particularly because of datadir_source in copy_file_range. Not worth
>> it.
>
> Forgot that:
>     if (ControlFile_target.state != DB_SHUTDOWNED)
>         pg_fatal("target server must be shut down cleanly\n");
> We may want to allow a target node shutdowned in recovery as well here.

So, attached is a more polished version of this patch, cleaned up of
its typos with as well other things. I have noticed for example that
it would be more useful to add the debug information of a timeline
file fetched from the source or a target server directly in
getTimelineHistory. I have as well updated a couple of comments in the
code regarding the fact that we do not necessarily use a master as a
target node, and mentioned in findCommonAncestorTimeline that we check
as well the start position of a timeline to cover the case where both
target and source node forked at the same timeline number but with a
different WAL fork position.
I am marking this patch as ready for committer. It would be cool in
the future to use the recovery test suite to have more advanced
scenarios tested, but it seems a shame to block this patch because of
that.