protected void startMaster(ServerName server) throws IOException {
    getLogger().info("Starting master {}", server.getHostname());
    cluster.startMaster(server.getHostname(), server.getPort());
    cluster.waitForActiveAndReadyMaster(startMasterTimeout);
    getLogger().info("Started master " + server.getHostname());
  }
Returns current region servers - active master
hbase-it/src/test/java/org/apache/hadoop/hbase/chaos/actions/Action.java