protected void killNameNode(ServerName server) throws IOException {
    getLogger().info("Killing namenode {}", server.getHostname());
    cluster.killNameNode(server);
    cluster.waitForNameNodeToStop(server, killNameNodeTimeout);
    getLogger().info("Killed namenode {}. Reported num of rs:{}", server,
      cluster.getClusterMetrics().getLiveServerMetrics().size());
  }
Returns current region servers - active master
hbase-it/src/test/java/org/apache/hadoop/hbase/chaos/actions/Action.java