[jira] [Created] (KAFKA-20796) num-open-iterators metric under-counts iterators from MeteredTimestampedKeyValueStore

["Jess Jin (Jira)" <ji...@apache.org>]

Jess Jin created KAFKA-20796:
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             Summary: num-open-iterators metric under-counts iterators from MeteredTimestampedKeyValueStore
                 Key: KAFKA-20796
                 URL: https://issues.apache.org/jira/browse/KAFKA-20796
             Project: Kafka
          Issue Type: Improvement
          Components: streams
            Reporter: Jess Jin


MeteredTimestampedKeyValueStoreIterator(streams/src/main/java/org/apache/kafka/streams/state/internals/MeteredTimestampedKeyValueStore.java:301) registers itself in {{openIterators}} but never calls {{{}numOpenIterators.increment () / decrement(){}}}.

As a result, iterators opened against a plain (non-headers) timestamped key-value store are invisible to the '{{{}num-open-iterators{}}}' metric while still visible to '{{{}oldest-iterator-open-since-ms{}}}' - the two gauges disagree about how many iterators are open.

Fix: call {{numOpenIterators.increment()}} in the constructor and {{numOpenIterators.decrement()}} in {{close()}}.



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