Re: Quorum commit for multiple synchronous replication.

On Wed, Sep 7, 2016 at 4:03 AM, Josh Berkus <josh@agliodbs.com> wrote:
> On 08/29/2016 06:52 AM, Fujii Masao wrote:
>> Also I like the following Simon's idea.
>>
>> https://www.postgresql.org/message-id/CANP8+jLHfBVv_pW6grASNUpW+bdk5DcTu7GWpNAP-+-ZWvKT6w@mail.gmail.com
>> -----------------------
>> * first k (n1, n2, n3) – does the same as k (n1, n2, n3) does now
>> * any k (n1, n2, n3) – would release waiters as soon as we have the
>> responses from k out of N standbys. “any k” would be faster, so is
>> desirable for performance and resilience
>
> What are we going to do for backwards compatibility, here?
>
> So, here's the dilemma:
>
> If we want to keep backwards compatibility with 9.6, then:
>
> "k (n1, n2, n3)" == "first k (n1, n2, n3)"
>
> However, "first k" is not what most users will want, most of the time;
> users of version 13, years from now, will be getting constantly confused
> by "first k" behavior when they wanted quorum.  So the sensible default
> would be:
>
> "k (n1, n2, n3)" == "any k (n1, n2, n3)"
>

+1.

"k (n1, n2, n3)" == "first k (n1, n2, n3)" doesn't break backward
compatibility but most users would think "k(n1, n2, n3)" as quorum
after introduced quorum.
I wish we can change the s_s_names syntax of 9.6 to "first k(n1, n2,
n3)" style before 9.6 releasing if we got consensus.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center