Dane Miller <dane at greatschools.net> writes:
> Christopher Browne wrote:
>> Consider:
>> - Nodes 1-3 are in a LAN at Data Centre A
>> - Nodes 4-6 are in a LAN at Data Centre B
>> 
>> There are constrictions...
>> - 1-3 can easily "talk amongst themselves."
>> - Likewise, 4-6 can easily "talk amongst themselves."
>> - However, we pick #3 and #4 as being the only nodes that are allowed
>>   to talk with one another across the WAN
>> 
>> There are configurations you cannot create, in such a case:
>> - You cannot have any configuration where nodes 5 or 6 subscribe
>> directly to
>>   1-3; they *MUST* go thru node 4
>> - Likewise, you cannot have any configuration where nodes 1 or 2
>>   subscribe directly to 4-6; they *MUST* go thru node 3 
>
> This is similar to a setup I was managing at my site until recently.  We
> gave up because, to follow this example, events from nodes 5 and 6 were
> making their way to nodes 1-3.  It was easy to configure the proper
> parent for each node, which determined the data path data.  But I wasn't
> sure how to setup Slony replication such that there were no listen paths
> between nodes 5, 6 and 1-3.
>
> Our requirement was that nodes 1-3 were not allowed to know about or be
> influenced by any events on nodes 5 and 6.  5 and 6 should communicate
> only with node 4, which in turn would communicate with nodes 1-3.  Is
> this possible?  Doesn't 'store path()' create listen paths between all
> cluster nodes?

You're fighting against how Slony-I was designed.

All nodes need to be aware of all other nodes; that's essential to
(for instance) how the data purging policy was designed.

Log data cannot be purged from nodes 1-3 until they *know* that the
events have been processed by nodes 4, 5, and 6.

If you "win the fight" and get Slony-I configured to *not* have listen
paths between 1-3 and 5,6, you'll find that things break down because
obsolete data won't ever get purged.
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