Re: Behaviour of take over the synchronous replication

On 08/23/2013 12:42 AM, Sawada Masahiko wrote:
> in case (a), those priority is clear. So I think that re-taking over
> is correct behaviour.
> OHOT, in case (b), even if AAA and BBB are set same priority, AAA
> server steals SYNC replication.
> I think it is better that BBB server continue behaviour SYNC standby,
> and AAA should become potential server.

So, you're saying that:

1) synchronous_standby_names = '*'

2) replica 'BBB' is the current sync standby

3) replica 'AAA' comes online

4) replica 'AAA' grabs sync status

?

If that's the case, I'm not really sure that's undesirable behavior.
One could argue fairly persuasively that if you care about the
precendence order of sync replicas, you shouldn't use '*'.  And the rule
of "if using *, the lowest-sorted replica name has sync" is actually a
predictable, easy-to-understand rule.

So if you want to make this a feature request, you'll need to come up
with an argument as to why the current behavior is bad.  Otherwise,
you're just asking us to document it better (which is a good idea).

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com