Why not to support registerSeekCallback and onPartitionsAssigned to batchListener?

[realcbb]

Code in KafkaMessageListenerContainer:

		if (listener instanceof BatchMessageListener) {
			this.listener = null;
			this.batchListener = (BatchMessageListener<K, V>) listener;
			this.isBatchListener = true;
		}

Why not set this.listener = listener, otherwise, registerSeekCallback and onPartitionsAssigned can be supported.

[garyrussell]

It's a bug.

[realcbb]

Thanks for the feedback.
Also I dont know why consumerAware and retry are not supported to batchListener.
For retry feature, retry is on "onMessage" method rather than consumer's poll method. Why should not end-users have the retry on the whole batch?

[garyrussell]

Retry is left to the user because the framework has no idea where in the batch the failure occurred; you can simply use a RetryTemplate within your listener.

There is a BatchConsumerAwareMessageListener.

[realcbb]

I think, the framework does not need to know where in the batch the failure occurred. Just retry the process in onMessage method.

When using @KafkaListener, it seems that BatchComsumerAwareMessageListener will not be auto created, and some error occurred such like List or List must be the only parameter.

[garyrussell]

Yes, but if the batch fails in the middle, the whole batch will be retried. I don't think the framework can make any assumptions that the listener can handle duplicate messages; it's really a function inside the listener.

The error when trying to use a Consumer<?, ?> parameter with a batch @KafkaListener is another bug.

Thanks for giving the 2.0 milestone(s) a spin - useful feedback; thanks!

[realcbb]

Thanks for your great work!

Besides, is there any possible to support this feature:
When errors occurred during processing messages from consumer's poll, auto-seek to the position of partitions before this poll? Maybe that's not a good idea...

[garyrussell]

Perhaps we could add a ConsumerAwareErrorHandler (and the batch version) and implementations that do as you suggest.

[realcbb]

Thank you very much!