@Override
	public void add(IndexRequest... indexRequests) {
		Collections.addAll(bufferedRequests, indexRequests);
	}
Implementation of a {@link RequestIndexer} that buffers {@link ActionRequest ActionRequests}
before re-sending them to the Elasticsearch cluster upon request.
elasticsearch5-xh/elasticsearch5-xh-sink/src/main/java/org/apache/flink/streaming/connectors/elasticsearch/BufferingNoOpRequestIndexer.java