From: Noah Misch <noah@leadboat.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: masahiko.sawada@2ndquadrant.com
Cc: masao.fujii@oss.nttdata.com
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Race condition in SyncRepGetSyncStandbysPriority
Date: Tue, 14 Apr 2020 20:14:02 -0700
Message-ID: <20200415031402.GA959799@rfd.leadboat.com> (raw)
In-Reply-To: <13059.1586896360@sss.pgh.pa.us>
References: <20200413.153101.688623432137444694.horikyota.ntt@gmail.com>
<8325.1586828060@sss.pgh.pa.us>
<CA+fd4k4f+QrGOpEMR3GA6yHakCr6ssJB_EbRrdC-=miwEZf3mQ@mail.gmail.com>
<20200414.183538.344904915964423903.horikyota.ntt@gmail.com>
<15616.1586872362@sss.pgh.pa.us>
<13059.1586896360@sss.pgh.pa.us>
On Tue, Apr 14, 2020 at 04:32:40PM -0400, Tom Lane wrote:
> I wrote:
> > It doesn't seem to me to be that hard to implement the desired
> > semantics for synchronous_standby_names with inconsistent info.
> > In FIRST mode you basically just need to take the N smallest
> > priorities you see in the array, but without assuming there are no
> > duplicates or holes. It might be a good idea to include ties at the
> > end, that is if you see 1,2,2,4 or 1,3,3,4 and you want 2 sync
> > standbys, include the first three of them in the calculation until
> > the inconsistency is resolved. In ANY mode I don't see that
> > inconsistent priorities matter at all.
>
> Concretely, I think we ought to do the attached, or something pretty
> close to it.
>
> I'm not really happy about breaking ties based on walsnd_index,
> but I see that there are several TAP test cases that fail if we
> do something else. I'm inclined to think those tests are bogus ...
> but I won't argue to change them right now.
This passes the test battery I wrote in preparation for the 2020-02 thread.
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To: pgsql-hackers@postgresql.org
Cc: noah@leadboat.com, tgl@sss.pgh.pa.us, horikyota.ntt@gmail.com, masahiko.sawada@2ndquadrant.com, masao.fujii@oss.nttdata.com, pgsql-hackers@lists.postgresql.org
Subject: Re: Race condition in SyncRepGetSyncStandbysPriority
In-Reply-To: <20200415031402.GA959799@rfd.leadboat.com>
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