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3. Reverse mirroring again. Cluster A stores LMLE 3 in the internal topic, and cluster B queries this LMLE and truncate records beyond leader epoch 3. 


Please note that after LMLE truncation, it doesn't mean the log between 2 clusters are in sync. It only means the leader epoch history is in sync. The leader epoch history (i.e. the leader-epoch-checkpoint file in the partition directory) contains the entry for each [leader epoch, start offset]. However, the log might still not converge, yet. In the example below, after cluster B truncates LMLE 3, the offset 4 (in leader epoch 3) still exists, which is inconsistent with the source cluster. In this case, the second log truncation will be triggered by the replication protocol by the last fetched leader epoch comparison. So the offset 4 will be truncated this time, and the logs in these 2 clusters are completely in sync.

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