public void setFailureHandler(ActionRequestFailureHandler<DocWriteRequest<?>> failureHandler) {
            this.failureHandler = Preconditions.checkNotNull(failureHandler);
        }
Sets a failure handler for action requests.

@param failureHandler This is used to handle failed {@link ActionRequest}.
inlong-sort/sort-flink/sort-flink-v1.13/sort-connectors/elasticsearch-6/src/main/java/org/apache/inlong/sort/elasticsearch6/ElasticsearchSink.java