Status

Current state:  "Under Discussion"Adopted

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]
JIRA:  link

Vote thread: link

JIRA:

• Jira
  server ASF JIRA serverId 5aa69414-a9e9-3523-82ec-879b028fb15b key KAFKA-12944

   (3.0)

• Jira
  server ASF JIRA serverId 5aa69414-a9e9-3523-82ec-879b028fb15b key KAFKA-13093

   (3.1)

• Jira
  server ASF JIRA serverId 5aa69414-a9e9-3523-82ec-879b028fb15b key KAFKA-12872

   (4.0)
  

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

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Produce and fetch requests with v0 and v1 message formats would will be supported via up-conversion and down-conversion. Up-conversion and (especially) down-conversion have measurable performance impact due to increased CPU and memory usage, but the vast majority of Kafka clients have supported v2 for some time (even Spark, a notable late adopter, has supported v2 since Spark 2.4, which was released in October 2018).

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On the consumer, it's more complicated. Brokers assume that consumers can read all message format versions and brokers never up-convert records when handling fetch responses. Furthermore, we cannot change the behavior of older broker versions. The options here are a bit complex and require more thought.