The getHashes() method calls getPrimary() to refresh the list of slaves. It is possible at the time this is called that no master is electable. And there's no point in checking the hashes for a node which is down. Furthermore, if we are given a list of slaves, we should not change this._master here. So if no list of slaves is provided, we should call _determineLiveSlaves() instead of getPrimary(). And if a list of slaves is provided, we should not call either method.