Re: BUG #4879: bgwriter fails to fsync the file in recovery mode

Simon Riggs wrote:
> On Thu, 2009-06-25 at 18:12 +0300, Heikki Linnakangas wrote:
>
>> A short fix would be to have bgwriter do the shutdown checkpoint instead
>> in archive recovery. I don't recall if there was a reason it wasn't
>> coded like that to begin with, though.
>
> I think the problem was that it was coded both ways at different stages
> of patch evolution. The decision to retain the shutdown checkpoint by
> the startup process was taken in January, IIRC.
>
> Having startup process issue this
>
> if (InArchiveRecovery)
> RequestCheckpoint(CHECKPOINT_IS_SHUTDOWN |
> CHECKPOINT_FORCE |
> CHECKPOINT_WAIT)
> else
>
> should make the startup process wait for bgwriter to complete the
> checkpoint. But we need to set LocalRecoveryInProgress appropriately
> also.

Yeah, the trouble is to tell bgwriter that it's OK for it to create the
checkpoint, which includes writing a WAL record, while still keeping the
system "in-recovery" for all other purposes. While we could just relax
the checks, that seems like a very important safeguard.

(I posted in the other mail to do a restartpoint before the startup
process does the checkpoint)

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com