@Override
	public void doManualAck(LinkedList<MessageHeaders> messageHeadersList) {
		Iterator<MessageHeaders> iterator = messageHeadersList.iterator();
		while (iterator.hasNext()) {
			MessageHeaders headers = iterator.next();
			Acknowledgment acknowledgment = (Acknowledgment) headers.get(KafkaHeaders.ACKNOWLEDGMENT);
			Assert.notNull(acknowledgment, "Acknowledgement shouldn't be null when acknowledging kafka message " +
					"manually.");
			acknowledgment.acknowledge();
		}
	}
Fetches partition data, throwing an exception if the expected number is not met after a number of
subsequent retries
@param topicName topic
@param expectedNumber expected number of partitions. If less or equal to 0, check is suppressed.
@return the partitions
spring-xd-messagebus-kafka/src/main/java/org/springframework/xd/dirt/integration/kafka/KafkaMessageBus.java