[jira] [Created] (KAFKA-14856) Next gen group coordinator dynamic configs should be forward compatible

["Jeff Kim (Jira)" <ji...@apache.org>]

Jeff Kim created KAFKA-14856:
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             Summary: Next gen group coordinator dynamic configs should be forward compatible
                 Key: KAFKA-14856
                 URL: https://issues.apache.org/jira/browse/KAFKA-14856
             Project: Kafka
          Issue Type: Task
            Reporter: Jeff Kim
            Assignee: Jeff Kim


The quorum controller does not delete any ConfigRecords when downgrading the MetadataVersion. When a downgraded broker starts, it does not perform any validation on the configs and only dynamic configs known to the downgraded broker will be visible and handled. Specifically, the two dynamic configs introduced in [KIP-848|https://cwiki.apache.org/confluence/display/KAFKA/KIP-848%3A+The+Next+Generation+of+the+Consumer+Rebalance+Protocol] will be of a new resource type GROUP and will be completely ignored by the existing coordinator. This code path will change once KIP-848 is implemented and it should also only handle known configs to make it forward compatible.


One scenario to consider is when brokers are at the same MV but are running different software where one set supports new dynamic configs and the other does not. To remove this discrepancy, new dynamic configs should be gated by MV.



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