public void setBackoffType(FlushBackoffType backoffType) {
			this.backoffType = checkNotNull(backoffType);
		}
Provides a backoff policy for bulk requests. Whenever a bulk request is rejected due to resource constraints
(i.e. the client's internal thread pool is full), the backoff policy decides how long the bulk processor will
wait before the operation is retried internally.

<p>This is a proxy for version specific backoff policies.
elasticsearch5-xh/elasticsearch5-xh-sink/src/main/java/org/apache/flink/streaming/connectors/elasticsearch/ElasticsearchSinkBase.java