@Override
        public boolean equals(Object obj) {
            if (! (obj instanceof Nodes b)) return false;
            if (logicalNodeCount != b.logicalNodeCount) return false;
            if (type != b.type) return false;
            if (!upNodes.equals(b.upNodes)) return false;
            if (!nodeStates.equals(b.nodeStates)) return false;
            return true;
        }
Maintains a bitset where all non-down nodes have a bit set. All nodes that differ from defaultUp
and defaultDown are stored explicitly in a hash map.
vdslib/src/main/java/com/yahoo/vdslib/state/ClusterState.java