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";
    private static final String NUMBER_OF_IN_FLIGHT_FETCH = "number_of_in_flight_fetch";