Re: Sync Rep v19

On Sat, Mar 19, 2011 at 11:28 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Fri, Mar 18, 2011 at 10:25 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> On Tue, Mar 8, 2011 at 7:05 AM, Fujii Masao <masao.fujii@gmail.com> wrote:
>>> * Smart shutdown
>>> Smart shutdown should wait for all the waiting backends to be acked, and
>>> should not cause them to forcibly exit. But this leads shutdown to get stuck
>>> infinitely if there is no walsender at that time. To enable them to be acked
>>> even in that situation, we need to change postmaster so that it accepts the
>>> replication connection even during smart shutdown (until we reach
>>> PM_SHUTDOWN_2 state). Postmaster has already accepted the superuser
>>> connection to cancel backup during smart shutdown. So I don't think that
>>> the idea to accept the replication connection during smart shutdown is so
>>> ugly.
>>>
>>> * Fast shutdown
>>> I agree with you about fast shutdown. Fast shutdown should cause all the
>>> backends including waiting ones to exit immediately. At that time, the
>>> non-acked backend should not return the success, according to the
>>> definition of sync rep. So we need to change a backend so that it gets rid
>>> of itself from the waiting queue and exits before returning the success,
>>> when it receives SIGTERM. This change leads the waiting backends to
>>> do the same even when pg_terminate_backend is called. But since
>>> they've not been acked yet, it seems to be reasonable to prevent them
>>> from returning the COMMIT.
>>>
>>> Comments? I'll create the patch barring objection.
>>
>> The fast smart shutdown part of this problem has been addressed.  The
>
> Ugh.  I mean "the fast shutdown", of course, not "the fast smart
> shutdown".  Anyway, point is:
>
> fast shutdown now OK
> smart shutdown still not OK
> do you want to write a patch?
>
> :-)
>
>> smart shutdown case still needs work, and I think the consensus was
>> that your proposal above was the best way to go with it.
>>
>> Do you still want to work up a patch for this?  If so, I can review.

Sure. Will do.

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center