Ah, good point. Thanks for the responses, everybody.

So, there seems to be a consensus that A needs to know about C (or vice
versa), in my example? Apart from the failover case you just mentioned,
why is that? Allowing C to be ignorant of A would seem to allow for A to
fail without having any effect on C's replication. 

As it is, in an A failure case, does the configuration for C need to
change? 

One question just leads to another with me....

- DAP

-----Original Message-----
From: slony1-general-bounces at gborg.postgresql.org
[mailto:slony1-general-bounces at gborg.postgresql.org] On Behalf Of
Christopher Browne
Sent: Monday, July 26, 2004 1:53 PM
To: Darcy Buskermolen
Cc: slony1-general at gborg.postgresql.org
Subject: Re: [Slony1-general] replication chain

Darcy Buskermolen <darcy at wavefire.com> writes:
> On July 26, 2004 08:43 am, David Parker wrote:
>> Say I have 2 geographically separated data centers, East and West, 
>> where is West is the "warm" backup for East. In East I have 2 
>> databases, A and B, where B is a "hot" backup for A, so A is the 
>> "master" in that replication cluster.
>>
>> I'm wondering about the best way to set up replication for my 
>> database C, in the West data center. It is the second level back for 
>> A, but I would like to avoid adding the load on A of having C making 
>> requests against it to get updates.
>>
>> My thought was that I could set up B as the master for C, so when B 
>> replicated from A, it would trigger a further replication to C, but C

>> would only need to connect to B. So the replication chain would be:
>> A->B->C.
>
> This is an exact feature of Slony I.
>>
>> Would this work, or does C need a connection to A for some reason?
> Node B subscribes to node A, and Node C subscribes to Node B, Node A 
> does not need to know Node C exists.

You probably also want a plan to be able to reconfigure A and C to be
able to talk directly supposing B should happen to get "taken out."

This is also a sort of "exact feature" of Slony-I...
--
"cbbrowne","@","ca.afilias.info"
<http://dev6.int.libertyrms.com/>
Christopher Browne
(416) 673-4124 (land)
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