Hi there,

>> No, 1.2 does not work with 8.4, and barring having considerably more
>> time to play with, it doesn't seem like a straightforward backport.
>>
>> There were substantial changes in 8.4 to the implementation of
>> pg_listener, to change from on-table storage to an in-memory handling
>> that would fairly much break the whole listener loop.
>>
>> Version 2.0 revised that substantially; that doesn't seem like a
>> backport, though.
> 
> This is really a major problem.
> upgrade to slony-1 2.x require to rebuild the whole cluster.
> upgrade to pgsql-8.4 require to rebuild the whole database.

I agree with Laurent here.

> I cannot find a way to upgrade to 8.4 without innaceptable downtime
> unless we upgrade both psql and slony at once :(

Anyway, even upgrading both psql and slony at once will cause a big
downtime :-(

We'll have same problems, in many production environments for customers.

Cheers,

-- 
Jean-Paul Argudo
www.PostgreSQLFr.org
www.Dalibo.com