Richard Yen <dba at richyen.com> writes:
>> I'm curious as to why you expect there to be less network traffic.  It
>> seems to me that the main traffic would come from query application,
>> and I don't see any reason for the change you are suggesting to cut
>> down on that.
>>
> Well, the way we've got this set up is table X has copies of itself on
> three clusters.  So among the three clusters, there's already network
> connections open to each of their respective nodes.  The new thing we
> want to do is to create a "master copy" of table X, so that we can
> just update once, and the changes would propagate to the three other
> clusters.  If each node in each cluster were to create a new network
> connection to this "master copy" node, that would increase network
> traffic; if we just left it to the providers on each cluster to
> propagate to its subscribers, we'd use existing network connections,
> and it would possibly be cleaner.  Hence, the desire for the table to
> subscribe via one setID, and provide via another setID.
>
>> The *possible* change would be for there to be less network traffic as
>> a result of fewer events propagating, but I don't see that changing
>> network traffic particularly materially.
> True.  In terms of net bytes transferred, there's no difference.  I
> suppose it's just the thought of more network connections that
> initially raises flags.

Idle thinking...  If you separate that table into its own set, you
ought to be able to set up whatever cascading you want, and that
should allow minimizing the amount of traffic...

I notice you indicate three clusters.  By that, do you mean that you
have 3 Slony-I clusters?  That is, 3 separate cluster names, each with
its own set of nodes and such?  That's not going to "share" terribly
well, because the design of things is for those clusters to be
essentially unable to perceive one another.

If you do indeed mean 3 clusters, then the way I'd expect to need to
do this is to create a 4th cluster for propagation of this table.
That unfortunately means extra slons, extra connections, and such.
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