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Re: Quorum commit for multiple synchronous replication.

Michael Paquier <michael.paquier@gmail.com>

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From: Michael Paquier <michael.paquier@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Fujii Masao <masao.fujii@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Petr Jelinek <petr@2ndquadrant.com>, Vik Fearing <vik@2ndquadrant.fr>, Simon Riggs <simon@2ndquadrant.com>, Josh Berkus <josh@agliodbs.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2016-12-06T10:14:31Z
Lists: pgsql-hackers 
On Tue, Dec 6, 2016 at 6:57 PM, Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> On Tue, Dec 6, 2016 at 1:11 PM, Fujii Masao <masao.fujii@gmail.com> wrote:
>> If M (i.e., number of quorum sync standbys) is enough large,
>> your choice would be good. But usually M seems not so large.
>>
>
> Thank you for the comment.
>
> One another possible idea is to use the partial selection sort[1],
> which takes O(MN) time. Since this is more efficient if N is small
> this would be better than qsort for this case. But I'm not sure that
> we can see such a difference by result of performance measurement.
>
> [1] https://en.wikipedia.org/wiki/Selection_algorithm#Partial_selection_sort

We'll begin to see a minimal performance impact when selecting a sync
standby across hundreds of them, which is less than say what 0.1% (or
less) of existing deployments are doing. The current approach taken
seems simple enough to be kept, and performance is not something to
worry much IMHO.
-- 
Michael

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Set the priorities of all quorum synchronous standbys to 1.

  2. Improve documentation and comment for quorum-based sync replication.