nicktelford commented on code in PR #17713:
URL: https://github.com/apache/kafka/pull/17713#discussion_r1833719869
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streams/src/main/java/org/apache/kafka/streams/state/internals/MeteredKeyValueStore.java:
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@@ -154,7 +155,13 @@ private void registerMetrics() {
StateStoreMetrics.addNumOpenIteratorsGauge(taskId.toString(),
metricsScope, name(), streamsMetrics,
(config, now) -> numOpenIterators.sum());
StateStoreMetrics.addOldestOpenIteratorGauge(taskId.toString(),
metricsScope, name(), streamsMetrics,
- (config, now) -> openIterators.isEmpty() ? null :
openIterators.first().startTimestamp()
+ (config, now) -> {
+ try {
+ return openIterators.isEmpty() ? null :
openIterators.first().startTimestamp();
Review Comment:
Actually, another option is to use `ConcurrentSkipListMap<MeteredIterator,
Object>`. This is actually what `ConcurrentSkipListSet` uses internally, and
`ConcurrentSkipListMap` provides `firstEntry()`, which returns `null` when
empty.
The downside of this is that everwhere that adds to `openIterators` would
need to use a dummy value (`ConcurrentSkipListSet` uses `Boolaen.TRUE`), which
might look a bit odd.
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