From: | Noah Misch <noah(at)leadboat(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, masahiko(dot)sawada(at)2ndquadrant(dot)com, masao(dot)fujii(at)oss(dot)nttdata(dot)com, pgsql-hackers(at)lists(dot)postgresql(dot)org |
Subject: | Re: Race condition in SyncRepGetSyncStandbysPriority |
Date: | 2020-04-15 03:14:02 |
Message-ID: | 20200415031402.GA959799@rfd.leadboat.com |
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Lists: | pgsql-hackers |
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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