Re: Checkpoint not retrying failed fsync?

On Fri, Apr 6, 2018 at 11:34 AM, Andrew Gierth
<andrew(at)tao11(dot)riddles(dot)org(dot)uk> wrote:
>>>>>> "Thomas" == Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> writes:
>
> >> As far as I can tell from reading the code, if a checkpoint fails the
> >> checkpointer is supposed to keep all the outstanding fsync requests for
> >> next time. Am I wrong, or is there some failure in the logic to do this?
>
> Thomas> Yikes. I think this is suspicious:
>
> Yes, tracing through a checkpoint shows that this is clearly wrong.
>
> Thomas> Why is it OK to unlink the bitmapset? We still need its
> Thomas> contents, in the case that the fsync fails!
>
> Right.
>
> But I don't think just copying the value is sufficient; if a new bit was
> set while we were processing the old ones, how would we know which to
> clear? We couldn't just clear all the bits afterwards because then we
> might lose a request.

Agreed. The attached draft patch handles that correctly, I think.

--
Thomas Munro
http://www.enterprisedb.com