mjsax commented on code in PR #18771:
URL: https://github.com/apache/kafka/pull/18771#discussion_r1938345281
##########
streams/src/main/java/org/apache/kafka/streams/state/internals/MeteredKeyValueStore.java:
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@@ -156,11 +156,8 @@ private void registerMetrics() {
(config, now) -> numOpenIterators.sum());
StateStoreMetrics.addOldestOpenIteratorGauge(taskId.toString(),
metricsScope, name(), streamsMetrics,
(config, now) -> {
- try {
- return openIterators.isEmpty() ? null :
openIterators.first().startTimestamp();
- } catch (final NoSuchElementException ignored) {
- return null;
- }
+ final Iterator<MeteredIterator> openIteratorsIterator =
openIterators.iterator();
+ return openIteratorsIterator.hasNext() ?
openIteratorsIterator.next().startTimestamp() : null;
Review Comment:
https://www.javaspecialists.eu/archive/Issue288-Weakly-Consistent-Iteration.html
Refers to Java 16 (we are using 11 for Kafka Streams since AK 4.0).
This one seems to be more conclusive:
> Vector's Enumeration was neither fail-fast nor weakly-consistent. We could
create an Enumeration, but even if hasMoreElements() was true, nextElement()
could throw a NoSuchElementException. Also, with Vector if we removed an
element before our current position, then we would skip over the next element.
Similarly, adding an element before our current position would make us see
duplicate elements. These effects do not happen with weakly-consistent
iterators.
`These effects do not happen with weakly-consistent iterators.` seems to
refer to `NoSuchElementException`
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