Re: DRAFT 9.6 release

On 08/30/2016 02:28 PM, Bruce Momjian wrote:
> On Tue, Aug 30, 2016 at 09:41:59AM -0700, Josh Berkus wrote:
>> On 08/29/2016 06:24 PM, Amit Langote wrote:
>>> On 2016/08/30 8:00, Josh Berkus wrote:
>>>> Folks,
>>>>
>>>> Here is a preliminary draft of a 9.6 release announcement.
>>>>
>>>> Please comment, suggest, edit, make comments on the wiki, whatever.
>>>>
>>>> https://wiki.postgresql.org/wiki/96releasedraft
>>>
>>> In the section on scale out, I see quorum commit mentioned but it's not
>>> part of what's offered in 9.6.  The quorum part is still being worked on:
>>> https://commitfest.postgresql.org/10/696/
>>
>> Oh, figures the one feature I haven't tested would be the one which
>> isn't right.  So what DID get added to 9.6?  Is it still a significant
>> feature?
>
> We did this (from the 9.6 release notes):
>
>         Allow synchronous replication to support multiple simultaneous
>         synchronous standby servers, not just one (Masahiko Sawada,
>         Beena Emerson, Michael Paquier, Fujii Masao, Kyotaro Horiguchi)
>
>         The number of standby servers that must acknowledge a commit
>         before it is considered complete is now configurable as part of
>         the synchronous_standby_names parameter.
>
> You can see the details here, e.g. "3 (s1, s2, s3, s4)"
>
>     https://www.postgresql.org/docs/9.6/static/runtime-config-replication.html#GUC-SYNCHRONOUS-STANDBY-NAMES

So that's usually what I mean when I say quorum commit.  But apparently
our feature does something slightly different?

"For example, a setting of 3 (s1, s2, s3, s4) makes transaction commits
wait until their WAL records are received by three higher-priority
standbys chosen from standby servers s1, s2, s3 and s4"

What does that mean exactly?  If I do:

3 ( s1, s2, s3, s4, s5 )

And a commit is ack'd by s2, s3, and s5, what happens?




--
--
Josh Berkus
Red Hat OSAS
(any opinions are my own)