I had the same situation. A change is queued up for the
install docs about this.  Yes, build against both.
Yes, use MASTERPORT, SLAVEPORT. You are on the right track.

--elein

On Fri, Aug 27, 2004 at 06:00:01PM -0600, Brian Hirt wrote:
> 
> Hi, i have a simple question about installing slony that i didn't see 
> in the docs.
> 
> If i have two postmasters running on the same machine, one running 
> 8.0beta1 and one running 7.4.5, do i need to install slony twice, once 
> with the --with-pgsourcetree=7.4.5 and once with 
> --with-pgsourcetree=8.0.  If so, do i have to use different --prefix 
> for each slony installation?
> 
> i sent a message a day or so ago about  using slony to help upgrade 
> between releases with as little downtime as possible.   I understand 
> it's basically the same as setting up a master->slave and then failing 
> over, but i wonder if we should have a seperate howto for using slony 
> to upgrade?   For example the question i ask here would probably be a 
> common scenario that isn't mentioned in howto_install and while 
> howto_basic talks about replicating between two databases on the same 
> host, it doesn't talk about replicating between two databases on the 
> same host under different postmasters.  That might be as simple as 
> adding MASTERPORT and SLAVEPORT to the current documentation and 
> appropriate commands.
> 
> I'm happy to add my experiences to the documentation, but i don't know 
> how it would be most appreciated.
> 
> --brian
> 
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