kamalcph commented on code in PR #14004:
URL: https://github.com/apache/kafka/pull/14004#discussion_r1267015333
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storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/RemoteLogLeaderEpochState.java:
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@@ -100,17 +100,29 @@ void
handleSegmentWithCopySegmentStartedState(RemoteLogSegmentId remoteLogSegmen
void handleSegmentWithCopySegmentFinishedState(Long startOffset,
RemoteLogSegmentId remoteLogSegmentId,
Long leaderEpochEndOffset) {
+ // If there are duplicate segments uploaded due to leader-election,
then mark them as unreferenced.
+ // Duplicate segments can be uploaded when the previous leader had
tier-lags and the next leader uploads the
+ // segment for the same leader-epoch which is a super-set of
previously uploaded segments.
+ // (eg)
+ // case-1: Duplicate segment
+ // L0 uploaded segment S0 with offsets 0-100 and L1 uploaded
segment S1 with offsets 0-200.
+ // We will mark the segment S0 as duplicate and add it to
unreferencedSegmentIds.
+ // case-2: Overlapping segments
+ // L0 uploaded segment S0 with offsets 10-90 and L1 uploaded
segment S1 with offsets 5-100, S2-101-200,
+ // and so on. When the consumer request for segment with offset
95, it should get the segment S1 and not S0.
+ Map.Entry<Long, RemoteLogSegmentId> lastEntry = offsetToId.lastEntry();
+ while (lastEntry != null && lastEntry.getKey() >= startOffset &&
highestLogOffset <= leaderEpochEndOffset) {
Review Comment:
Thinking more on this, we may have to update the logic to find the
[copiedOffset](https://github.com/apache/kafka/blob/trunk/core/src/main/java/kafka/log/remote/RemoteLogManager.java#L499)
such that it's minimum of (end_offset_for_that_epoch_in_checkpoint_file,
highest_remote_offset). In this case, when B2 was leader, copied_offset should
be min(80, 112) where 80 is end_offset for LE0 and 112 is the
highest_remote_offset for LE0.
So, that B2 can able to upload the segment S2 (12:101)
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