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https://issues.apache.org/jira/browse/FLINK-40234?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martijn Visser updated FLINK-40234:
-----------------------------------
Priority: Critical (was: Major)
> Busy subtask thread may cause splits to be marked as idle erroneously and
> cause dropped records
> -----------------------------------------------------------------------------------------------
>
> Key: FLINK-40234
> URL: https://issues.apache.org/jira/browse/FLINK-40234
> Project: Flink
> Issue Type: Bug
> Components: Connectors / Kafka, Connectors / Parent
> Affects Versions: 2.3.0, 2.2.1
> Reporter: Keith Lee
> Assignee: Roman Khachatryan
> Priority: Critical
> Labels: pull-request-available
> Fix For: 2.4.0
>
>
> Consider the following:
> # WatermarksWithIdleness#onEvent() runs on subtask thread. It increments
> split activity whenever it is called.
> # WatermarksWithIdleness#checkIfIdle() also runs on subtask thread. It
> checks for idleness based on relative clock's elapsed time since inactivity
> was first detected[
> [https://github.com/apache/flink/blob/f9485ff173b940c5ddf606d8ca1a92a18bb23ff3/flink-core/src/main/java/org/apache/flink/api/common/eventtime/WatermarksWithIdleness.java#L140]|https://github.com/apache/flink/blob/f9485ff173b940c5ddf606d8ca1a92a18bb23ff3/flink-core/src/main/java/org/apache/flink/api/common/eventtime/WatermarksWithIdleness.java#L140]
> If individual records processing (also on subtask thread) takes a long time,
> records flow through slower and onEvent() for a split with records may not
> have been called yet because SourceOperator has not reach the same split. In
> this scenario, relative clock's elapsed time can exceed threshold and the
> split is marked as idle, even though the split has records. This can also
> occur in scenario like watermark crossing a HOP window's threshold,
> triggering the writes of aggregation results which also happens on subtask
> thread.
> See PR where unit test is added to demonstrate this issue
> [https://github.com/apache/flink/pull/28816]
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