public void close() {
        if (runner != null) {
            try {
                client.admin()
                        .indices()
                        .prepareFlush()
                        .setForce(true)
                        .execute()
                        .actionGet(ComponentUtil.getFessConfig().getIndexIndicesTimeout());
            } catch (final Exception e) {

                return Collections.emptyList();
            }
        };
        ComponentUtil.register(requestHeaderService, RequestHeaderService.class.getCanonicalName());

        final SetOnce<Map<String, Object>> initParamMapSet = new SetOnce<>();
        WebConfig webConfig = new WebConfig();
        webConfig.setUserAgent(Constants.CRAWLING_USER_AGENT_PREFIX + "1.0" + Constants.CRAWLING_USER_AGENT_SUFFIX);

                    source.put("timestamp", event.getTimestamp());
                    bulkRequest.add(client.prepareIndex().setIndex(indexName).setSource(source));
                }
                final BulkResponse response = bulkRequest.execute().actionGet(30_000L);
                if (response.hasFailures()) {