[jira] [Created] (KAFKA-7481) Consider options for safer upgrade of offset commit value schema

["Jason Gustafson (JIRA)" <ji...@apache.org>]

Jason Gustafson created KAFKA-7481:
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             Summary: Consider options for safer upgrade of offset commit value schema
                 Key: KAFKA-7481
                 URL: https://issues.apache.org/jira/browse/KAFKA-7481
             Project: Kafka
          Issue Type: Bug
            Reporter: Jason Gustafson
             Fix For: 2.1.0


KIP-211 and KIP-320 add new versions of the offset commit value schema. The use of the new schema version is controlled by the `inter.broker.protocol.version` configuration.  Once the new inter-broker version is in use, it is not possible to downgrade since the older brokers will not be able to parse the new schema. 

The options at the moment are the following:

1. Do nothing. Users can try the new version and keep `inter.broker.protocol.version` locked to the old release. Downgrade will still be possible, but users will not be able to test new capabilities which depend on inter-broker protocol changes.
2. Instead of using `inter.broker.protocol.version`, we could use `message.format.version`. This would basically extend the use of this config to apply to all persistent formats. The advantage is that it allows users to upgrade the broker and begin using the new inter-broker protocol while still allowing downgrade. But features which depend on the persistent format could not be tested.

Any other options?



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