smjn commented on code in PR #17149:
URL: https://github.com/apache/kafka/pull/17149#discussion_r1759221583
##########
share-coordinator/src/main/java/org/apache/kafka/coordinator/share/ShareCoordinatorShard.java:
##########
@@ -537,38 +539,308 @@ private static ShareGroupOffset merge(ShareGroupOffset
soFar, ShareUpdateValue n
.setStartOffset(newStartOffset)
.setLeaderEpoch(newLeaderEpoch)
.setStateBatches(combineStateBatches(currentBatches,
newData.stateBatches().stream()
- .map(PersisterOffsetsStateBatch::from)
- .collect(Collectors.toCollection(LinkedHashSet::new)),
newStartOffset))
- .build();
+ .map(ShareCoordinatorShard::toPersisterStateBatch)
+ .collect(Collectors.toList()), newStartOffset))
+ .build();
}
/**
- * Util method which takes in 2 collections containing {@link
PersisterOffsetsStateBatch}
+ * Util method which takes in 2 collections containing {@link
PersisterStateBatch}
* and the startOffset.
- * It removes all batches from the 1st collection which have the same
first and last offset
- * as the batches in 2nd collection. It then creates a final list of
batches which contains the
- * former result and all the batches in the 2nd collection. In set
notation (A - B) U B (we prefer batches in B
- * which have same first and last offset in A).
- * Finally, it removes any batches where the lastOffset < startOffset, if
the startOffset > -1.
- * @param currentBatch - collection containing current soft state of
batches
- * @param newBatch - collection containing batches in incoming request
+ * This method checks any overlap between current state batches and new
state batches.
+ * Based on various conditions it creates new non-overlapping records
preferring new batches.
+ * Finally, it removes any batches where the lastOffset < startOffset, if
the startOffset > -1 and
+ * merges any contiguous intervals with same state.
+ * @param batchesSoFar - collection containing current soft state of
batches
+ * @param newBatches - collection containing batches in incoming request
* @param startOffset - startOffset to consider when removing old batches.
* @return List containing combined batches
*/
- private static List<PersisterOffsetsStateBatch> combineStateBatches(
- Collection<PersisterOffsetsStateBatch> currentBatch,
- Collection<PersisterOffsetsStateBatch> newBatch,
+ // visibility for testing
+ static List<PersisterStateBatch> combineStateBatches(
+ List<PersisterStateBatch> batchesSoFar,
+ List<PersisterStateBatch> newBatches,
long startOffset
) {
- currentBatch.removeAll(newBatch);
- List<PersisterOffsetsStateBatch> batchesToAdd = new
LinkedList<>(currentBatch);
- batchesToAdd.addAll(newBatch);
- // Any batches where the last offset is < the current start offset
- // are now expired. We should remove them from the persister.
+ List<PersisterStateBatch> combinedList = new
ArrayList<>(batchesSoFar.size() + newBatches.size());
+ combinedList.addAll(batchesSoFar);
+ combinedList.addAll(newBatches);
+
+ // sort keeping delivery state in mind
+ combinedList.sort(PersisterStateBatch::compareTo);
+
+ return mergeBatches(
+ pruneBatches(
+ combinedList,
+ startOffset
+ )
+ );
+ }
+
+ private static class BatchOverlapState {
+ private final PersisterStateBatch last;
+ private final PersisterStateBatch candidate;
+ private final List<PersisterStateBatch> nonOverlapping;
+ public static final BatchOverlapState SENTINEL = new
BatchOverlapState(null, null, Collections.emptyList());
+
+ public BatchOverlapState(
+ PersisterStateBatch last,
+ PersisterStateBatch candidate,
+ List<PersisterStateBatch> nonOverlapping
+ ) {
+ this.last = last;
+ this.candidate = candidate;
+ this.nonOverlapping = nonOverlapping;
+ }
+
+ public PersisterStateBatch last() {
+ return last;
+ }
+
+ public PersisterStateBatch candidate() {
+ return candidate;
+ }
+
+ public List<PersisterStateBatch> nonOverlapping() {
+ return nonOverlapping;
+ }
+
+ @Override
+ public boolean equals(Object o) {
+ if (this == o) return true;
+ if (!(o instanceof BatchOverlapState)) return false;
+ BatchOverlapState that = (BatchOverlapState) o;
+ return Objects.equals(last, that.last) &&
Objects.equals(candidate, that.candidate) && Objects.equals(nonOverlapping,
that.nonOverlapping);
+ }
+
+ @Override
+ public int hashCode() {
+ return Objects.hash(last, candidate, nonOverlapping);
+ }
+ }
+
+ static List<PersisterStateBatch> mergeBatches(List<PersisterStateBatch>
batches) {
+ if (batches.size() < 2) {
+ return batches;
+ }
+ TreeSet<PersisterStateBatch> sortedBatches = new TreeSet<>(batches);
+ List<PersisterStateBatch> finalBatches = new
ArrayList<>(batches.size() * 2); // heuristic size
+
+ BatchOverlapState overlapState = getOverlappingState(sortedBatches);
+
+ while (overlapState != BatchOverlapState.SENTINEL) {
+ PersisterStateBatch last = overlapState.last();
+ PersisterStateBatch candidate = overlapState.candidate();
+
+ // remove non overlapping prefix from sortedBatches,
+ // will make getting next overlapping pair efficient
+ // as a prefix batch which is non overlapping will only
+ // be checked once.
+ if (overlapState.nonOverlapping() != null) {
+ overlapState.nonOverlapping().forEach(sortedBatches::remove);
+ finalBatches.addAll(overlapState.nonOverlapping());
+ }
+
+ if (candidate == null) {
+ break;
+ }
+
+ // overlap and same state (last.firstOffset <=
candidate.firstOffset due to sort
+ // covers:
+ // case: 1 2 3 4 5
6 7 (contiguous)
+ // last: ______ _______ _______ _______ _______
________ _______
+ // candidate: ______ ____ __________ ___ ____
_______ _______
+ if (compareBatchState(candidate, last) == 0) {
+ sortedBatches.remove(last); // remove older smaller interval
+ sortedBatches.remove(candidate);
+
+ last = new PersisterStateBatch(
+ last.firstOffset(),
+ // cover cases
+ // last: ______ ________ _________
+ // candidate: ___ __________ _____
+ Math.max(candidate.lastOffset(), last.lastOffset()),
+ last.deliveryState(),
+ last.deliveryCount()
+ );
+
+ sortedBatches.add(last);
+ } else if (candidate.firstOffset() <= last.lastOffset()) { // non
contiguous overlap
+ // overlap and different state
+ // covers:
+ // case: 1 2 3 4 5
6
+ // last: ______ _______ _______ _______
_______ ________
+ // candidate: ______ ____ _________ ____
____ _______
+ // max batches: 1 2 2 3
2 2
+ // min batches: 1 1 1 1
1 2
+
+ sortedBatches.remove(last);
+ if (candidate.firstOffset() == last.firstOffset()) {
+ if (candidate.lastOffset() == last.lastOffset()) { //
case 1
+ if (compareBatchState(candidate, last) < 0) { //
candidate is lower priority
+ sortedBatches.add(last);
Review Comment:
actually on second look, there is no state comparison needed. By nature of
the compareTo method we defined, conditate can never have lower priority if
last.firstOffset == candidate.firstOffset and last.lastOffset ==
candidate.lastOffset
will simplify the condition
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