mjsax commented on a change in pull request #10462:
URL: https://github.com/apache/kafka/pull/10462#discussion_r616269613
##########
File path:
streams/src/main/java/org/apache/kafka/streams/kstream/internals/KStreamKStreamJoin.java
##########
@@ -93,23 +136,118 @@ public void process(final K key, final V1 value) {
}
boolean needOuterJoin = outer;
+ boolean joinFound = false;
final long inputRecordTimestamp = context().timestamp();
final long timeFrom = Math.max(0L, inputRecordTimestamp -
joinBeforeMs);
final long timeTo = Math.max(0L, inputRecordTimestamp +
joinAfterMs);
+ maxObservedStreamTime.advance(inputRecordTimestamp);
+
try (final WindowStoreIterator<V2> iter = otherWindow.fetch(key,
timeFrom, timeTo)) {
while (iter.hasNext()) {
needOuterJoin = false;
+ joinFound = true;
final KeyValue<Long, V2> otherRecord = iter.next();
+ final long otherRecordTimestamp = otherRecord.key;
+
+ // Emit expired records before the joined record to keep
time ordering
+ emitExpiredNonJoinedOuterRecordsExcept(key,
otherRecordTimestamp);
+
context().forward(
key,
joiner.apply(key, value, otherRecord.value),
- To.all().withTimestamp(Math.max(inputRecordTimestamp,
otherRecord.key)));
+ To.all().withTimestamp(Math.max(inputRecordTimestamp,
otherRecordTimestamp)));
+ }
+
+ // Emit all expired records before adding a new non-joined
record to the store. Otherwise,
+ // the put() call will advance the stream time, which causes
records out of the retention
+ // period to be deleted, thus not being emitted later.
+ if (!joinFound && inputRecordTimestamp ==
maxObservedStreamTime.get()) {
+ emitExpiredNonJoinedOuterRecords();
}
if (needOuterJoin) {
- context().forward(key, joiner.apply(key, value, null));
+ // The maxStreamTime contains the max time observed in
both sides of the join.
+ // Having access to the time observed in the other join
side fixes the following
+ // problem:
+ //
+ // Say we have a window size of 5 seconds
+ // 1. A non-joined record wth time T10 is seen in the
left-topic (maxLeftStreamTime: 10)
+ // The record is not processed yet, and is added to
the outer-join store
+ // 2. A non-joined record with time T2 is seen in the
right-topic (maxRightStreamTime: 2)
+ // The record is not processed yet, and is added to
the outer-join store
+ // 3. A joined record with time T11 is seen in the
left-topic (maxLeftStreamTime: 11)
+ // It is time to look at the expired records. T10 and
T2 should be emitted, but
+ // because T2 was late, then it is not fetched by the
window store, so it is not processed
+ //
+ // See KStreamKStreamLeftJoinTest.testLowerWindowBound()
tests
+ //
+ // the condition below allows us to process the late
record without the need
+ // to hold it in the temporary outer store
+ if (!outerJoinWindowStore.isPresent() || timeTo <
maxObservedStreamTime.get()) {
Review comment:
Well, while we should have a check like this, it seems it should go to
the top of this method, next to the key/value `null` check? We should also add
a corresponding `lateRecordDropSensor` (cf `KStreamWindowAggregate.java`).
We can also `return` from `process()` early, as if we have a late record, we
know that stream-time does not advance and thus we don't need to emit anything
downstream.
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