Replication of databases (esp. postgres)

Hello altogether,

i'm breeding on a sensible concept to replicate a database
in a heterogenous environment while keeping the relations intact.

Given situation:

Database 1

Database 2

MASTER
Database 3

...

Database n

Every database replicates itself to MASTER which renumbers the
relations and which replicates the data to the rest of the databases.

All databases must have identical data. All databases have
tables with relations on unique indices. All databases are
granted i/u/d permissions on itself.

So any database may fire a trigger to insert, update or to delete
a record on any other database.

The shown scheme has the disadvantage to have two passes. One Transfer
of data from a slave to a master and one acknowledgement with corrected
relations from the master to the sending slave and replication traffic
to the other, receiving slaves.

Does anybody know how to implement another replication scheme?

Are there any info pointers on readings about replication of databases?

Are there any "ready to go out of the box" tools for postgres?

Thank you in advance.

t++