With a three node setup with two nodes of rank primary and one node of rank secondary, if the secondary node has the Master label the servers of rank primary are not used.

In cases where the rank mechanism is used to prefer certain servers but not exclude them in case a failover hapens, it would be desirable to use Slave servers of higher rank with a Master of lower rank. This should still remain configurable in case the rank mechanism is used to group servers together into logical pairs.