murphy pope <pope_murphy at hotmail.com> writes:

> I have a simple master/single-slave (ur, origin/single-subscriber) configuration that I'm testing.
> I've noticed that the origin slon process (node_1) opens a connection to the subscriber database (node_2) and
> listens on three different NOTIFY's:
> ??? _cluster_Event
> ??? _cluster_Confirm
> ??? _cluster_Node_1
> Why does the provider need to LISTEN for a notification on the
> subscriber?? What does the subscriber do that the origin needs to
> know about??

There is no such thing as an 'origin node' or a 'destination node;'
there are just 'nodes.'  A particular set may originate on a
particular node; that is not intrinsic in the nature of the node.  

And that can change; you could do a MOVE SET to switch the roles, at
which point the "now origin" needs to be listening to what is going on
on its provider.

> I think that the subscriber sends a confirmation to the origin, but
> that NOTIFY executes on the origin end doesn't it?

Probably so.

> If the origin didn't need to LISTEN for notifications that execute
> in the subscriber database, it wouldn't need a path (or a
> connection) to the subscriber.

> I have a feeling I'm missing something important here...

It's all in the fact that the notion of "origin" is tied to sets, not
to nodes.
-- 
"cbbrowne","@","ca.afilias.info"
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Christopher Browne
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