Re: Hot standby, recovery infra

Simon Riggs wrote:
> On Thu, 2009-01-29 at 19:20 +0200, Heikki Linnakangas wrote:
>> Hmm, seems like we haven't thought through how shutdown during
>> consistent recovery is supposed to behave in general. Right now, smart
>> shutdown doesn't do anything during consistent recovery, because the
>> startup process will just keep going. And fast shutdown will simply
>> ExitPostmaster(1), which is clearly not right.
>
> That whole area was something I was leaving until last, since immediate
> shutdown doesn't work either, even in HEAD. (Fujii-san and I discussed
> this before Christmas, briefly).

We must handle shutdown gracefully, can't just leave bgwriter running
after postmaster exit.

Hmm, why does pg_standby catch SIGQUIT? Seems it could just let it kill
the process.

>> I wonder if bgwriter should perform a restartpoint before exiting?
>> You'll have to start with recovery on the next startup anyway, but at
>> least we could minimize the amount of WAL that needs to be replayed.
>
> That seems like extra work for no additional benefit.
>
> I think we're beginning to blur the lines between review and you just
> adding some additional stuff in this area. There's nothing to stop you
> doing further changes after this has been committed.

Sure. I think the "shutdown restartpoint" might actually fall out of the
way the code is structured anyway: bgwriter normally performs a
checkpoint before exiting.

> We can also commit
> what we have with some caveats also, i.e. commit in pieces.

This late in the release cycle, I don't want to commit anything that we
would have to rip out if we run out of time. There is no difference from
review or testing point of view whether the code is in CVS or not.

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