Nickstery commented on code in PR #14004:
URL: https://github.com/apache/kafka/pull/14004#discussion_r1267954353
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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:
Test example
```
@Test
void
handleSegmentWithCopySegmentFinishedStateForDuplicateSegmentsWithSecondSegmentEarlierEndOffset()
{
// Broker-1 is a Leader for Partition-0, Broker-2 is follower
RemoteLogSegmentId segmentId1BRoker1 = new RemoteLogSegmentId(tpId,
Uuid.randomUuid());
//Leader and follower are in sync
epochState.handleSegmentWithCopySegmentFinishedState(10L,
segmentId1BRoker1, 100L);
//Broker-1 received some messages and part of them were replicated
by follower
// Broker-2 was not able to replicate all the messages because
Broker-1 is died.
// But it was able to upload segment before death [101, 200]
RemoteLogSegmentId segmentId2Broker1 = new RemoteLogSegmentId(tpId,
Uuid.randomUuid());
epochState.handleSegmentWithCopySegmentFinishedState(101L,
segmentId2Broker1, 200L);
// Broker-2 still in-sync according to `replica.lag.time.max.ms`
// Last offset in sync is 150L
// Broker-2 gets the leadership and fills the segment 101L-190L and
uploads to Tiered storage
RemoteLogSegmentId segmentId2Broker2 = new RemoteLogSegmentId(tpId,
Uuid.randomUuid());
epochState.handleSegmentWithCopySegmentFinishedState(101L,
segmentId2Broker2, 190L);
//Traffic stops
//Since LeaderEpoch was changed, I expect that more fresh data will
be on the TS
assertEquals(190L, epochState.highestLogOffset());
//segment 2 uploaded by Broker-1 is expected to be unreferenced
assertTrue(epochState.unreferencedSegmentIds().contains(segmentId2Broker1));
assertEquals(1, epochState.unreferencedSegmentIds().size());
}```
Than it could be part of integration test, we can upload new segment [191L,
300L] and consume from the beginning from TS. With current logic we have data
loss from segment 2 where BROKER-2 was leader [151L,190L], but in case of Kafka
local storage functionality, it would not happen
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