Hi! I'm a maintainer of an open source Kafka client and working on adding support for kafka-stored offsets. The client works fine with v0 of the OffsetCommit/OffsetFetch messages, but with v1+ it always fails to fetch the offset. I've been digging quite a bit and found that the OffsetCommit appears to work - I'm able to verify using command line tools. However, the OffsetFetch response always response with error code 3 (UNKNOWN_TOPIC_OR_PARTITION).
I'm sending the message to the coordinator node for the consumer group and I've also tried manually sending the message to the other nodes in my test cluster. I have tried enabling TRACE-level logging and it shows the request being received and replied to (it appears to be being parsed correctly, so I don't think my message is corrupt) but I don't see anything else telling in the logs. I realize it's hard to debug this without code. I can actually share the code since it's an open source client, but my hope is that someone recognizes this problem and has a quick answer. My test cluster is Kafka 0.11. Thanks! - Dan
