Thanks for the feedback, Matthias.
My original intention was that the RebalanceConsumer would be a view with
limited operations, and so would be closed after each rebalance is completed to
prevent caching the object after exiting the callback. I thought making it
closeable would signal that.
And it would allows us to do something like
try (var view = createRebalanceConsumer(…)) {
listener.onPartitionsAssigned(partitions, view);
} and throw an IllegalStateExeption if someone invokes methods on consumer
later.
But I see that that just means users can invoke close() themselves
mid-rebalance which is not desirable.
I think we can achieve the same try-with-resources in the impl and not the
public interface.
Thanks for the catch. I’ve updated the KIP
-Aditya
> On Jun 2, 2026, at 10:17, Matthias J. Sax <[email protected]> wrote:
>
> Hey,
>
> sorry for late reply, but I am wondering why the new `RebalanceConsumer`
> interface would extend `AutoClosable`?
>
> I don't think that `close()` would be a safe operation during a rebalance,
> and the goal of the KIP is explicitly to only expose safe operations.
>
>
> -Matthias
>
>> On 5/29/26 10:38 PM, Aditya Kousik wrote:
>> Thanks Chia-Ping.
>> chia_00: I’ve updated the JavaDoc (I realised it was lacking more detail
>> that I have in the actual PR). In this case, yes each invocation replaces
>> the previously set object. The final value before the subsequent poll() will
>> be the one to receive callbacks during rebalance events.
>> Thanks,
>> Aditya
>>>> On May 29, 2026, at 21:48, Chia-Ping Tsai <[email protected]> wrote:
>>>
>>> hi Aditya
>>>
>>> chia_00: What happens if a user calls setRebalanceListener(listener)
>>> multiple times? I assume the previous listener will be replaced. If so,
>>> could you please explicitly state this behavior in the Javadoc?
>>>
>>> Best,
>>> Chia-Ping
>>>
>>>> On 2026/04/01 15:16:36 Aditya Kousik wrote:
>>>> Hi all,
>>>>
>>>> I'd like to start a discussion on KIP-1306: RebalanceHandler:
>>>> Consumer-Aware Rebalance Callback.
>>>>
>>>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-1306%3A+RebalanceHandler%3A+Consumer-Aware+Rebalance+Callback
>>>>
>>>> Spring Kafka, SmallRye, and Micronaut all pass the consumer into rebalance
>>>> callbacks; the client doesn't. The standard workaround of
>>>> constructor-injecting a full Consumer reference allows dangerous
>>>> operations like poll() and close() inside a callback. This KIP proposes
>>>> RebalanceHandler, with a RebalanceConsumerView that exposes only safe
>>>> operations, making misuse a compile error.
>>>>
>>>> Looking forward to your feedback.
>>>>
>>>> Thanks
>>>>
>
