postgres 9.1 master-master setup using Bucardo
Solution 1:
Bucardo only needs to be installed on one host, although obviously, that won't provide HA capability. Typically, in a master-master scenario, it's installed on one of the masters. In the event either of the masters then goes down, the Bucardo daemon wouldn't have anything to do anyway, so HA for it is pretty moot.
Some useful links:
http://justatheory.com/computers/databases/postgresql/bootstrap-bucardo-mulitmaster.html
http://blog.endpoint.com/2011/06/bucardo-multi-master-for-postgresql.html