Re: Time-Delayed Standbys

(2013/12/04 4:00), Andres Freund wrote:
> On 2013-12-03 13:46:28 -0500, Robert Haas wrote:
>> On Tue, Dec 3, 2013 at 12:36 PM, Fabrízio de Royes Mello
>> <fabriziomello(at)gmail(dot)com> wrote:
>>> On Tue, Dec 3, 2013 at 2:33 PM, Christian Kruse <christian(at)2ndquadrant(dot)com>
>>> wrote:
>>>>
>>>> Hi Fabrizio,
>>>>
>>>> looks good to me. I did some testing on 9.2.4, 9.2.5 and HEAD. It
>>>> applies and compiles w/o errors or warnings. I set up a master and two
>>>> hot standbys replicating from the master, one with 5 minutes delay and
>>>> one without delay. After that I created a new database and generated
>>>> some test data:
>>>>
>>>> CREATE TABLE test (val INTEGER);
>>>> INSERT INTO test (val) (SELECT * FROM generate_series(0, 1000000));
>>>>
>>>> The non-delayed standby nearly instantly had the data replicated, the
>>>> delayed standby was replicated after exactly 5 minutes. I did not
>>>> notice any problems, errors or warnings.
>>>>
>>>
>>> Thanks for your review Christian...
>>
>> So, I proposed this patch previously and I still think it's a good
>> idea, but it got voted down on the grounds that it didn't deal with
>> clock drift. I view that as insufficient reason to reject the
>> feature, but others disagreed.
>
> I really fail to see why clock drift should be this patch's
> responsibility. It's not like the world would go under^W data corruption
> would ensue if the clocks drift. Your standby would get delayed
> imprecisely. Big deal. From what I know of potential users of this
> feature, they would set it to at the very least 30min - that's WAY above
> the range for acceptable clock-drift on servers.
Yes. I think that purpose of this patch is long time delay in standby server,
and not for little bit careful timing delay.

Regards,
--
Mitsumasa KONDO
NTT Open Source Software Center