protected void killMaster(ServerName server) throws IOException {
    getLogger().info("Killing master {}", server);
    cluster.killMaster(server);
    cluster.waitForMasterToStop(server, killMasterTimeout);
    getLogger().info("Killed master " + server);
  }
Returns current region servers - active master
hbase-it/src/test/java/org/apache/hadoop/hbase/chaos/actions/Action.java