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https://issues.apache.org/jira/browse/KAFKA-12457?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17299936#comment-17299936
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Justine Olshan commented on KAFKA-12457:
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Thanks for creating this JIRA. There is some discussion on sentinel topic IDs
in KIP-516 as well, but it has been a while since we discussed this. I think
the original plan was to use the sentinel ID as a sort of bootstrap for Vote
requests and then to generate a unique topic ID for the metadata topic. Very
much open to discussion and potential changes though.
[https://cwiki.apache.org/confluence/display/KAFKA/KIP-516%3A+Topic+Identifiers#KIP516:TopicIdentifiers-CompatibilitywithKIP-500]
> Implications of KIP-516 for quorum controller
> ---------------------------------------------
>
> Key: KAFKA-12457
> URL: https://issues.apache.org/jira/browse/KAFKA-12457
> Project: Kafka
> Issue Type: Improvement
> Reporter: Jason Gustafson
> Priority: Major
> Labels: kip-500
>
> KIP-516 introduces topic IDs to Kafka. We are in the process of updating many
> of the protocols to support them. In most cases, we are dropping the topic
> name entirely from new API versions. I think there are two open questions for
> KIP-500 in regard to this:
> 1. Can we assume topic ID existence in KIP-500?
> I think the answer here is yes, and the existing code already assumes it. The
> nice thing is that KIP-516 brings with it the logic to create topic IDs for
> existing topics. We can rely on this ability in the bridge release to ensure
> that all topics have topic IDs. And we can add it to pre-upgrade validations.
> 2. What topic ID should be used for `@metadata`?
> There are basically two options for this: either use a sentinel topic ID or
> let the controller generate a new one and write it into a `TopicRecord` when
> the cluster first initializes. If we assume long term that we won't be able
> to use topic names in the inter-broker protocol, then a sentinel might really
> be a necessity since brokers would need to know the topic ID before they can
> send fetches. In other words, if we generate a unique ID, then we probably
> still need some sentinel so that followers can fetch the initial
> `TopicRecord` which contains the ID.
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