kamalcph commented on code in PR #14004: URL: https://github.com/apache/kafka/pull/14004#discussion_r1268399339
########## storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/RemoteLogLeaderEpochState.java: ########## @@ -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: @satishd @Nickstery Correct me If I'm wrong: The logic to find the `copiedOffset` from remoteStorage doesn't take in account of the current-leader-epoch checkpoint file. In the above test, when B2 becomes leader, it's leader-epoch-checkpoint file will look like: (The case mentioned in the test can happen when acks is set to 1) ``` 0 2 0 0 1 151 ``` The logic to find the copied offset traverses the checkpoint file from latest-epoch. So, when B2 tries to find the copied offset: For epoch(1), there won't any uploaded segments, so it returns empty. For epoch(0), the highest copied offset will be 200 So, B2 will skip the segment S2 (101-190) which means there is a data loss from [151-190] @Nickstery This can be fixed if we update the logic to find the `copiedOffset`: ``` find-highest-remote-offset = min(end-offset-for-epoch-in-the-checkpoint, highest-remote-offset-for-epoch) ``` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: jira-unsubscr...@kafka.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org