Re: Quorum commit for multiple synchronous replication.

From: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
To: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Cc: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Petr Jelinek <petr(at)2ndquadrant(dot)com>, Vik Fearing <vik(at)2ndquadrant(dot)fr>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Quorum commit for multiple synchronous replication.
Date: 2016-12-16 05:38:21
Message-ID: 20161216053821.GA17838@paquier.xyz
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On Thu, Dec 15, 2016 at 6:08 PM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> Attached latest v12 patch.
> I changed behavior of "N (standby_list)" to use the priority method
> and incorporated some review comments so far. Please review it.

Some comments...

+ Another example of <varname>synchronous_standby_names</> for multiple
+ synchronous standby is:
Here standby takes an 's'.

+ candidates. The master server will wait for at least 2 replies from them.
+ <literal>s4</> is an asynchronous standby since its name is not in the list.
+ </para>
"will wait for replies from at least two of them".

+ * next-highest-priority standby. In quorum method, the all standbys
+ * appearing in the list are considered as a candidate for quorum commit.
"the all" is incorrect. I think you mean "all the" instead.

+ * NIL if no sync standby is connected. In quorum method, all standby
+ * priorities are same, that is 1. So this function returns the list of
This is not true. Standys have a priority number assigned. Though it does
not matter much for quorum groups, it gives an indication of their position
in the defined list.

#synchronous_standby_names = '' # standby servers that provide sync rep
- # number of sync standbys and comma-separated list of application_name
+ # synchronization method, number of sync standbys
+ # and comma-separated list of application_name
# from standby(s); '*' = all
The formulation is funny here: "sync rep synchronization method".

I think that Fujii-san has also some doc changes in his box. For anybody
picking up this patch next, it would be good to incorporate the things
I have noticed here.
--
Michael

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