PostgreSQL has master-slave replication (one read/write master, and multiple read-only standbys), the other users are talking about multi-master replication (all the databases are read/write).

I'm aware. What I'm asking is why multi master is required. You can have a read only slave that is promoted to the master. It's that little bit of downtime during failover in question? Doesn't pgpool make that possible without downtime?

If you use multi master and DNS failover you still have partial downtime for every session routed to the unhealthy master. That doesn't seem to solve the problem, just a little better.

Yup. The synchronous replication described in the docs will allow the configuration of a hot standby, but I don’t think it allows writing to the standby, which is what true master-master does.