public static UUID getUUIDForCluster(ZKWatcher zkw) throws KeeperException {
    String uuid = readClusterIdZNode(zkw);
    return uuid == null ? null : UUID.fromString(uuid);
  }
Get the UUID for the provided ZK watcher. Doesn't handle any ZK exceptions
@param zkw watcher connected to an ensemble
@return the UUID read from zookeeper
@throws KeeperException if a ZooKeeper operation fails
hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKClusterId.java