My patch is only able to add "random" load balancing though, not "round-robin". So this patch still definitely seems useful, even when mine gets merged.
I'm not sure that the support for the "working" connection is necessary from a feature perspective though (usability/discoverability is another question). It's already possible to achieve the same behaviour by simply providing multiple host names in the connection string. You can even tell libpq to connect to a primary or secondary by using the target_session_attrs option.
