Hi,
I am using Kafka for a fairly specific use case with a need for a lot of control. I use the new KafkaConsumer to consume events from input topic, process the data and publish to multiple different topics. The use case requires fairly strict delivery and consistency guarantees. All messages must be published to the resulting topics "exactly once". I am using ExactlyOnceDeliveryConsumerRebalanceListener to handle cases where the message is published, but the consumer dies before committing the offset which would normally result in a at least once delivery guarantee and therefore possibly duplicated messages, because after a rebalance new consumer in the group would publish the same uncommited offset again. Therefore I am using an ExactlyOnceDeliveryConsumerRebalanceListener to perform correcting actions during group rebalance after a failure. I am using a SimpleConsumer (for granular control and ability to read/commit using the original consumer group) to find these issues and publish the partially processed records as necessary and most importantly commit the offset to avoid duplicates if required. The result of 'simpleConsumer. commitOffsets(new OffsetCommitRequest(group, topicPartition))' however is 'OffsetCommitResponse(Map([topic,0] -> 25),0)', i.e. UNKNOWN_MEMBER_ID error. Can anyone please explain why I might be getting this error and how to avoid it in my scenario? Thank you, Martin
