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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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Roman Khachatryan updated FLINK-40234:
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    Component/s: Connectors / Kafka
                 Connectors / Parent
                     (was: Runtime / Task)

> 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: Major
>              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 records processing (also 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.
> See PR where unit test is added to demonstrate this issue
> [https://github.com/apache/flink/pull/28816]



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