private static final Logger logger = LogManager.getLogger(DataIndexHelper.class);

    private static final String DELETE_OLD_DOCS = "delete_old_docs";

    private static final String KEEP_EXPIRES_DOCS = "keep_expires_docs";

    protected long crawlingExecutionInterval = Constants.DEFAULT_CRAWLING_EXECUTION_INTERVAL;

    protected int crawlerPriority = Thread.NORM_PRIORITY;