private void checkErrorAndRethrow() {
		Throwable cause = failureThrowable.get();
		if (cause != null) {
			throw new RuntimeException("An error occurred in ElasticsearchSink.", cause);
		}
	}
Build the {@link BulkProcessor}.

<p>Note: this is exposed for testing purposes.
elasticsearch5-xh/elasticsearch5-xh-sink/src/main/java/org/apache/flink/streaming/connectors/elasticsearch/ElasticsearchSinkBase.java