[jira] [Created] (KAFKA-19485) Acknowledgements should not be sent on initial epoch of ShareFetch

["Shivsundar R (Jira)" <ji...@apache.org>]

Shivsundar R created KAFKA-19485:
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             Summary: Acknowledgements should not be sent on initial epoch of ShareFetch
                 Key: KAFKA-19485
                 URL: https://issues.apache.org/jira/browse/KAFKA-19485
             Project: Kafka
          Issue Type: Sub-task
            Reporter: Shivsundar R


There are some race scenarios in multi-broker environments where acknowledgements are sent on an initial epoch in a ShareSession.

This could arise if
 # Consumer subscribed to a partition whose leader was node-0.
 # Broker restart happens and node-0 is elected leader again. Broker starts a new ShareSession.
 # Background thread sends a fetch request with non-zero epoch.
 # Broker responds with SHARE_SESSION_NOT_FOUND.
 # Client updates session epoch to 0 once it receives this error. 
 # Application thread processing the previous fetch, completes and sends acks to piggyback on next fetch.
 # Next fetch will send the piggyback acknowledgements on the fetch resulting in error from broker ("Acknowledgments sent on initial epoch").


*Fix :*  Add a check before sending out acknowledgments if we are on an initial epoch.



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