Subject: Client development - OffsetFetch request always returns UNKNOWN_TOPIC_OR_PARTITION


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