@Override
  public void nodeDeleted(String path) {
    // We need to keep track of the cluster's shutdown status while
    // we wait on the current master. We consider that, if the cluster
    // was already in a "shutdown" state when we started, that this master
    // is part of a new cluster that was started shortly after the old cluster
    // shut down, so that state is now irrelevant. This means that the shutdown
    // state must be set while we wait on the active master in order
    // to shutdown this master. See HBASE-8519.
    if (path.equals(watcher.getZNodePaths().clusterStateZNode) && !master.isStopped()) {
      clusterShutDown.set(true);
    }
    handle(path);
  }
@param watcher ZK watcher
@param sn      ServerName
@param master  In an instance of a Master.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/ActiveMasterManager.java