* if too many empty results are encountered or if a system shutdown is requested.
     */
    @Override
    public void run() {
        if (dataService == null) {
            throw new FessSystemException("DataService is null. IndexUpdater cannot proceed without a DataService instance.");
        }

        if (logger.isDebugEnabled()) {
            logger.debug("Starting indexUpdater.");
        }

        final OpenSearchUrlQueueService urlQueueService = ComponentUtil.getComponent(OpenSearchUrlQueueService.class);
        final OpenSearchDataService dataService = ComponentUtil.getComponent(OpenSearchDataService.class);

        try {
            // clear url filter
            urlFilterService.delete(sid);
        } catch (final Exception e) {