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1. The broker opens a Log instance for all partitions on its local disk, including stray partitions.
2. Retention would not delete any segments for stray partitions. Retention starts deleting segments only when the high watermark is higher than the segment's last offset. A stray partition is not a valid replica anymore, and thus has no defined high watermark. This means the disk space for stray partitions can never be reclaimed.
3. If a broker hosts a stray partition and the topic is recreated, there is no protection in place to be able to distinguish the current stray partition from the new partition. In the worst case, this means data for the previous generation of the partition will now reside in the current generation.

This KIP proposes a mechanism to clean up stray partitions, solving problems (1) and (2) listed above. (3) is mitigated to an extent but we would require the improvements that are part of KIP-516: Topic Identifiers.

Public Interfaces

We propose to change the LeaderAndIsrRequest to include an additional containsAllReplicas field, denoting whether the request contains the full replica list hosted by the target broker.

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