David Darville <david at darville.name> writes:
> On Wed, Jan 05, 2005 at 01:03:17PM +0000, David Darville wrote:
>
>> But when moving origin of the set from node 1 to node 2, I end up with
>> having node 1 forward all changes to node 3. And what I really need is a way
>> to take down node 1 for maintenance, and that I cannot do while it forwards
>> to node 3.
>> I can only see 2 ways to change that - either I can unsubscribe node 3 and
>> subscribe it with node 2 as provider, but that locks down node 3 for quite a
>> while, or I could do a failover instead, and risk loosing some data.
>
> I have now found a 3rd solution, using the following script to move the
> origin of the set from node 1 to node 2:
>
> echo 'Locking set 1 on node 1';
> lock set (id = 1, origin = 1);
> wait for event ( origin = 1, confirmed = 2 );
>
> try
> {
>    echo 'Trying to mode set 1 from 1 to 2';
>    move set (id = 1, old origin = 1, new origin = 2);
> }
> on error
> {
>    echo 'ERROR - unlocking set 1 on node 1';
>    unlock set (id = 1, origin = 1);
> }
>
> echo 'Changing subscription of node 3 to 2';
> subscribe set ( id = 1, provider = 2, receiver = 3, forward = yes );
> wait for event ( origin = 3, CONFIRMED = 2 );
>
> echo 'Restarting node 3';
> restart node 3;
>
>
> And it looks like it is working, but I am not certain if this is can
> cause problems or not, especially since I have to restart node 3
> after resubscribingit. Could someone with a deeper understanding of
> Slony-I please comment on this.

I'm not sure what problems you're anticipating here.

I'm a little surprised that you needed to do anything particularly to
node 3 after pointing its subscription to node 2.

The thing you should check for is that there is an sl_listen entry
that allows node #3 to get events from node #2 directly from node #2.
I recently ran into a "situation" where, absent of that, and in the
presence of node 3 looking for node 2 events on node 1, the
"resubscribe" didn't take effect because it wasn't getting updates
directly enough fron node #2.

If what you're wondering is "Should I use SUBSCRIBE SET to repoint
node 3 to node 2?", then the answer is "absolutely yes, that's the
right thing to do."
-- 
"cbbrowne","@","ca.afilias.info"
<http://dev6.int.libertyrms.com/>
Christopher Browne
(416) 673-4124 (land)