Re: Kafka Producer send offsets to transaction method confusion

Thanks for reaching out. This is actually very good feedback.

In general, it seems that `ConsumerGroupMetadata` should be an
interface, not a class, making it impossible for users to create an
instance.

Of course, we cannot do anything for older releases, and it seems the
JavaDocs do explain it correctly...

But I did file https://issues.apache.org/jira/browse/KAFKA-18836 -- feel
free to pick it up if you have interest to contribute a fix for Apache
Kafka 4.1 release.


-Matthias


On 2/19/25 9:17 AM, Paweł Szymczyk wrote:
> Hello!
>
> Recently, I had an opportunity to work with legacy code that was using an
> old version of the Kafka native producer transactional API. Our goal was to
> upgrade the code to the newest version and benefit from the upgraded
> transactional API protocol. Initially, we found code that was highlighted
> as deprecated (
> https://kafka.apache.org/25/javadoc/org/apache/kafka/clients/producer/Producer.html#sendOffsetsToTransaction-java.util.Map-java.lang.String-
> ):
>
>> kafkaProducer.sendOffsetsToTransaction(Map.of(new
>> TopicPartition(record.topic(), record.partition()), new
>> OffsetAndMetadata(record.offset())), groupId);
>>
>
> Our first approach was to use the non-deprecated API:
>
> kafkaProducer.sendOffsetsToTransaction(Map.of(new
>> TopicPartition(record.topic(), record.partition()), new
>> OffsetAndMetadata(record.offset())), new ConsumerGroupMetadata(groupId));
>
>
> A few days later, after an extensive testing session, we finally read the
> new sendOffsetsToTransaction method javadoc and discovered that we needed
> to retrieve metadata from the Kafka Consumer.
>
> From our perspective, this upgrade process was more complicated than
> expected and requires broad knowledge of the transactional protocol
> upgrade. Are there any contradictions in making the public
> ConsumerGroupMetadata(String
> groupId) constructor deprecated too? It would have given us a clear hint
> that we were still doing something wrong from the start.
>