Currently my customer has some very large stand-alone PostgreSQL 9.6 (will migrate next year to v13) databases, and they want to add HA.
Specifically, they want a "cluster name" which points to a Primary database server's IP address, and and which automatically (presumably through through a heartbeat and quorum voting system) points to a Secondary database server's IP address if the Primary server goes down. Both servers are in the same data center. (Replication would be handled by a standard PostgreSQL method.)
This is not load balancing, but a purely HA solution.
I looked at HAProxy, but it seems to be focused on load balancing, while the Patroni documentation does not seem to mention a cluster name.