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https://issues.apache.org/jira/browse/KAFKA-7481?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16656026#comment-16656026
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Dong Lin commented on KAFKA-7481:
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Thanks for the detailed explanation [~hachikuji]. I agree with your short term
and long term solution. I assume previously when we upgrade the consumer offset
topic schema version, we have the same issue of not being able to downgrade the
Kafka broker version after the schema version has been upgraded. So this is the
status quo.
I took a look at the upgrade.html. It seems that we currently don't have
downgrade note. Maybe we need to additionally note in the upgrade.html that
after user bumps up the inter.broker.protocol to 2.1.0, they can no longer
downgrade the server version to be below 2.1.0.
> 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
> Priority: Blocker
> 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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