- private Map<HighLevelClient, Node> clientNodes = Collections.synchronizedMap(new HashMap<HighLevelClient, Node>());
+ private final Map<HighLevelClient, Node> clientNodes = Collections.synchronizedMap(new HashMap<HighLevelClient, Node>());
+
+ /** Collection of currently connected nodes. */
+ private final Set<Node> connectedNodes = Collections.synchronizedSet(new HashSet<Node>());