@Override
    public void add(DocWriteRequest<?> request) {
        if (flushOnCheckpoint) {
            numPendingRequestsRef.getAndIncrement();
        }
        this.bulkProcessor.add(request);
    }
Implementation of a {@link RequestIndexer}, using a {@link BulkProcessor}. {@link ActionRequest
ActionRequests} will be buffered before sending a bulk request to the Elasticsearch cluster.

<p>Note: This class is binary compatible to Elasticsearch 7.
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/elasticsearch-7/src/main/java/org/apache/inlong/sort/elasticsearch7/Elasticsearch7BulkProcessorIndexer.java