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https://issues.apache.org/jira/browse/FLINK-12872?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Piotr Nowojski updated FLINK-12872:
-----------------------------------
Priority: Not a Priority (was: Minor)
> WindowOperator may fail with UnsupportedOperationException when merging
> windows
> -------------------------------------------------------------------------------
>
> Key: FLINK-12872
> URL: https://issues.apache.org/jira/browse/FLINK-12872
> Project: Flink
> Issue Type: Bug
> Components: API / DataStream
> Affects Versions: 1.6.4, 1.7.2, 1.8.0
> Reporter: Piotr Nowojski
> Priority: Not a Priority
> Labels: auto-deprioritized-major, stale-minor
>
> [Reported
> |http://mail-archives.apache.org/mod_mbox/flink-user/201906.mbox/%3CCALDWsfhbP6D9+pnTzYuGaP0V4nReKJ4s9VsG_Xe1hZJq4O=z...@mail.gmail.com%3E]
> by a user.
> {noformat}
> I have a job that uses processing time session window with inactivity gap of
> 60ms where I intermittently run into the following exception. I'm trying to
> figure out what happened here. Haven't been able to reproduce this scenario.
> Any thoughts?
> java.lang.UnsupportedOperationException: The end timestamp of a
> processing-time window cannot become earlier than the current processing time
> by merging. Current processing time: 1560493731808 window:
> TimeWindow{start=1560493731654, end=1560493731778}
> at
> org.apache.flink.streaming.runtime.operators.windowing.WindowOperator$2.merge(WindowOperator.java:325)
> at
> org.apache.flink.streaming.runtime.operators.windowing.WindowOperator$2.merge(WindowOperator.java:311)
> at
> org.apache.flink.streaming.runtime.operators.windowing.MergingWindowSet.addWindow(MergingWindowSet.java:212)
> at
> org.apache.flink.streaming.runtime.operators.windowing.WindowOperator.processElement(WindowOperator.java:311)
> at
> org.apache.flink.streaming.runtime.io.StreamInputProcessor.processInput(StreamInputProcessor.java:202)
> at
> org.apache.flink.streaming.runtime.tasks.OneInputStreamTask.run(OneInputStreamTask.java:105)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:300)
> at org.apache.flink.runtime.taskmanager.Task.run(Task.java:711)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> This is happening probably because {{System.currentTimeMillis()}} is not a
> monotonic function and {{WindowOperator}} accesses it at least twice: once
> when it creates a window and second time during performing the above
> mentioned check (that has failed). However I would guess there are more
> places like this, not only in {{WindowOperator}}.
> The fix could be either to make sure that processing time is monotonic, or to
> access it only once per operator per record or to drop processing time in
> favour of ingestion time.
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