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https://issues.apache.org/jira/browse/FLINK-10050?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16880103#comment-16880103
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Kostas Kloudas commented on FLINK-10050:
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Hi [~klion26] ! I agree that the user should be able to get the side output
containing the late data. So we should essentially align the semantics and the
functionality of the CoGroupedStreams with the one of the WindowedStream. If I
am not mistaken, this means exposing from the CoGroupedStreams the
WindowedStreams.sideOutputLateData(), right?
> Support 'allowedLateness' in CoGroupedStreams
> ---------------------------------------------
>
> Key: FLINK-10050
> URL: https://issues.apache.org/jira/browse/FLINK-10050
> Project: Flink
> Issue Type: New Feature
> Components: API / DataStream
> Affects Versions: 1.5.1, 1.6.0
> Reporter: eugen yushin
> Priority: Major
> Labels: pull-request-available, ready-to-commit, windows
> Fix For: 1.7.0
>
>
> WindowedStream has a support of 'allowedLateness' feature, while
> CoGroupedStreams are not. At the mean time, WindowedStream is an inner part
> of CoGroupedStreams and all main functionality (like evictor/trigger/...) is
> simply delegated to WindowedStream.
> There's no chance to operate with late arriving data from previous steps in
> cogroups (and joins). Consider the following flow:
> a. read data from source1 -> aggregate data with allowed lateness
> b. read data from source2 -> aggregate data with allowed lateness
> c. cogroup/join streams a and b, and compare aggregated values
> Step c doesn't accept any late data from steps a/b due to lack of
> `allowedLateness` API call in CoGroupedStreams.java.
> Scope: add method `WithWindow.allowedLateness` to Java API
> (flink-streaming-java) and extend scala API (flink-streaming-scala).
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