private static final String CLUSTER_NAME = "cluster_name";
    private static final String STATUS = "status";
    private static final String TIMED_OUT = "timed_out";
    private static final String NUMBER_OF_NODES = "number_of_nodes";
    private static final String NUMBER_OF_DATA_NODES = "number_of_data_nodes";
    private static final String NUMBER_OF_PENDING_TASKS = "number_of_pending_tasks";

        assertTrue(mockConfig.getApiPingEsFieldSet().contains("status"));
        assertTrue(mockConfig.getApiPingEsFieldSet().contains("timed_out"));
        assertTrue(mockConfig.getApiPingEsFieldSet().contains("number_of_nodes"));
        assertTrue(mockConfig.getApiPingEsFieldSet().contains("number_of_data_nodes"));
        assertTrue(mockConfig.getApiPingEsFieldSet().contains("active_primary_shards"));

        private static final long serialVersionUID = 1L;

        @Override
        public String getApiPingSearchEngineFields() {

                    esClient.admin().cluster().prepareHealth().execute().actionGet(fessConfig.getIndexHealthTimeout());
            engineObj.clusterName = response.getClusterName();
            engineObj.numberOfNodes = response.getNumberOfNodes();
            engineObj.numberOfDataNodes = response.getNumberOfDataNodes();
            engineObj.activePrimaryShards = response.getActivePrimaryShards();