Re: Fast promotion failure

On Tue, May 7, 2013 at 6:57 PM, Heikki Linnakangas
<hlinnakangas(at)vmware(dot)com> wrote:
> While testing the bug from the "Assertion failure at standby promotion", I
> bumped into a different bug in fast promotion. When the first checkpoint
> after fast promotion is performed, there is no guarantee that the
> checkpointer process is running with the correct, new, ThisTimeLineID. In
> CreateCheckPoint(), we have this:
>
>> /*
>> * An end-of-recovery checkpoint is created before anyone is
>> allowed to
>> * write WAL. To allow us to write the checkpoint record,
>> temporarily
>> * enable XLogInsertAllowed. (This also ensures ThisTimeLineID is
>> * initialized, which we need here and in AdvanceXLInsertBuffer.)
>> */
>> if (flags & CHECKPOINT_END_OF_RECOVERY)
>> LocalSetXLogInsertAllowed();
>
>
> That ensures that ThisTimeLineID is updated when performing an
> end-of-recovery checkpoint, but it doesn't get executed with fast promotion.
> The consequence is that the checkpoint is created with the old timeline, and
> subsequent recovery from it will fail.
>
> I ran into this with the attached script. It sets up a master (M), a standby
> (B), and a cascading standby (C). I'm not sure why, but when I tried to
> simplify the script by removing the cascading standby, it started to work.
> The bug occurs in standby B, so I'm not sure why the presence of the
> cascading standby makes any difference. Maybe it just affects the timing.

Can this really happen? ISTM that the checkpointer should detect that
the recovery mode ends and call RecoveryInProgress()->InitXLOGAccess()
before calling CreateCheckPoint().

Regards,

--
Fujii Masao