String toString(boolean verbose) {
            StringBuilder sb = new StringBuilder();

            int nodeCount = verbose ? getLogicalNodeCount() : upNodes.length();
            if ( nodeCount > 0 ) {
                sb.append(type == NodeType.DISTRIBUTOR ? " distributor:" : " storage:").append(nodeCount);
                for (int i = 0; i < nodeCount; i++) {
                    String nodeState = getNodeState(i).serialize(i, verbose);
                    if (!nodeState.isEmpty()) {
                        sb.append(' ').append(nodeState);
                    }
                }
            }
            return sb.toString();
        }
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