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This KIP proposes adding the replica's HWM to the FETCH request so that the replica receiving the FETCH request can use the remote replica's HWM to determine if FETCH requests should be completed immediately or parked until there is new data or a new HWM.

Metadata Version

A new metadata version will be added. The replica fetcher with send the new FETCH rpc version (18) when the metadata version has been finalized to this new metadata version.

Fetch

Request

Add a version 18 of the RPC. Add the field HighWatermark which the replica sets to its known HWM. Set to -1 if the HWM is not known. The default value for the HWM is the largest int64 or 9223372036854775807.

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Kafka consumer and the replica fetcher should not set the HighWatermark field. The broker and replica manager will ignore the HighWatermark field if specified.A new metadata version will be added. The replica fetcher with send the new FETCH rpc version when the metadata version has been finalized to this new metadata version.

Compatibility, Deprecation, and Migration Plan

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