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• reverse.checkpointing.enabled (false) - Enables the new reverse checkpointing feature. Reverse checkpointing requires that there is an opposite, active flow, and the ReplicationPolicy implementation can tell what is the source cluster of a replica topic.

Proposed Changes

Currently, MirrorCheckpointConnector uses the offset-syncs of the same flow to generate checkpoints for downstream topics. This mechanism only allows translating offsets from upstream to downstream, and only applies to topics being replicated in the flow.

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With the above changes, all current features and guarantees of MirrorCheckpointConnector become available for reverse checkpoints: sync groups offsets, monotonic checkpoints, offset translation based on historical offset syncs.

Based on the previous points, there are 2 hard requirements for this feature to work:

1. An opposite, active flow exists - i.e. this feature only works in a bi-directional replication.
2. The ReplicationPolicy implementation can correctly report the source cluster of a topic (i.e. the "topicSource" method is correctly implemented).

Compatibility, Deprecation, and Migration Plan

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