Re: Sync Rep for 2011CF1

On 21.01.2011 15:24, Simon Riggs wrote:
> On Fri, 2011-01-21 at 14:45 +0200, Heikki Linnakangas wrote:
>> * it seems like overkill to not let clients to even connect when
>> allow_standalone_primary=off and no synchronous standbys are available.
>> What if you just want to run a read-only query?
>
> That's what Aidan requested, I agreed and so its there. You're using
> sync rep because of writes, so you have a read-write app. If you allow
> connections then half of the app will work, half will not. Half-working
> isn't very useful, as Aidan eloquently explained. If your app is all
> read-only you wouldn't be using sync rep anyway. That's the argument,
> but I've not got especially strong feelings it has to be this way.

It's also possible that most of your transactions in fact do "set
synchronous_replication=off", and only a few actually do synchronous
replication. It would be pretty bad to not allow connections in that
case. And what if you want to connect to the server to diagnose the
issue? Oh, you can't... Besides, we're not kicking out existing
connections, are we? Seems inconsistent to let the old connections live.

IMHO the only reasonable option is to allow connections as usual, and
only fail (or block forever) at COMMIT.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com