[jira] [Created] (KAFKA-14747) FK join should record discarded subscription responses

["Matthias J. Sax (Jira)" <ji...@apache.org>]

Matthias J. Sax created KAFKA-14747:
---------------------------------------

             Summary: FK join should record discarded subscription responses
                 Key: KAFKA-14747
                 URL: https://issues.apache.org/jira/browse/KAFKA-14747
             Project: Kafka
          Issue Type: Improvement
          Components: streams
            Reporter: Matthias J. Sax


FK-join are subject to a race condition. If the left-hand side record is updated, a subscription is sent to the right-hand side (including a hash value of the left-hand side record), and the right-hand side might send back join responses (also including the original hash). The left hand side only processed the responses if the hash matches, because a different hash implies that the left hand side row was updated in the mean-time (including sending a new subscription to the right hand side), and thus the data is stale and the response should not be processed.

A similar thing can happen on a right hand side update that triggers a response, that might be dropped if the left hand side row was updated in parallel.

While the behavior is correct, we don't record if this happens. We should consider to record this using the existing "dropped record" sensor or maybe add a new sensor.



--
This message was sent by Atlassian Jira
(v8.20.10#820010)