private static final String DELAYED_UNASSIGNED_SHARDS = "delayed_unassigned_shards";
    private static final String TASK_MAX_WAIT_TIME_IN_QUEUE_IN_MILLIS = "task_max_waiting_in_queue_millis";
    private static final String ACTIVE_SHARDS_PERCENT_AS_NUMBER = "active_shards_percent_as_number";
    private static final String ACTIVE_PRIMARY_SHARDS = "active_primary_shards";