Jess Jin created KAFKA-20902:
--------------------------------
Summary: Streams metered stores: oldest-iterator-open-since-ms can
be wrong when two iterators open in the same millisecond
Key: KAFKA-20902
URL: https://issues.apache.org/jira/browse/KAFKA-20902
Project: Kafka
Issue Type: Bug
Components: streams
Reporter: Jess Jin
{{openIterators}} is a {{ConcurrentSkipListSet}} keyed only by
{{startTimestamp()}} (ms resolution). Two iterators opened in the same
millisecond compare equal, so the second {{add()}} is a silent no-op and a
{{remove()}} on close can evict the still-open one — the
{{oldest-iterator-open-since-ms}} gauge then under-reports (may skip a
still-open iterator or return 0). {{num-open-iterators}} is unaffected
(separate {{LongAdder}}); iterators still close correctly, so it's a
metric-accuracy issue, not a leak. Affects all metered store wrappers. *Fix:*
make the comparator total (tie-break on a per-iterator sequence id). Found in
PR [#22975|https://github.com/apache/kafka/pull/22975] review
[{{r3730260330}}|https://github.com/apache/kafka/pull/22975#discussion_r3730260330].
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
