code: @Override
    public void onNodesUpdated(final List<NodeReport> nodeReports) {
      for (final NodeReport nodeReport : nodeReports) {
        this.nodeIdToRackName.put(nodeReport.getNodeId().toString(), nodeReport.getRackName());
        this.onNodeReport(nodeReport);
      }
    }
docs: RM Callback: RM reports status change of some nodes.
  @param nodeReports list of nodes with changed status.