versionId in responses (and general API versioning questions)
Just noticed that most of the API response structs do not include the
ApiVersion. This will make it hard for clients to determine how to
handle responses once the APIs start getting updated (which is pretty
I'd propose we update the standard response envelope to include it
Response => ApiVersion CorrelationId ResponseMessage
ApiVersion => int16
CorrelationId => int32
ResponseMessage => ...
Otherwise, it seems we must freeze the response formats forever.
Another thought is that the server should return the same version of the
API that was requested (if a client sends in v1, then presumably it does
know about any future versions...). How will this work? This seems to
imply backwards compat for the APIs like Avro.