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https://issues.apache.org/jira/browse/KAFKA-15417?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17762863#comment-17762863
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Matthias J. Sax commented on KAFKA-15417:
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Thanks a lot! Assigned the ticket to you.
> JoinWindow does not seem to work properly with a KStream - KStream -
> LeftJoin()
> --------------------------------------------------------------------------------
>
> Key: KAFKA-15417
> URL: https://issues.apache.org/jira/browse/KAFKA-15417
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Affects Versions: 3.4.0
> Reporter: Victor van den Hoven
> Assignee: Victor van den Hoven
> Priority: Major
> Attachments: SimpleStreamTopology.java, SimpleStreamTopologyTest.java
>
>
> In Kafka-streams 3.4.0 :
> According to the javadoc of the Joinwindow:
> _There are three different window configuration supported:_
> * _before = after = time-difference_
> * _before = 0 and after = time-difference_
> * _*before = time-difference and after = 0*_
>
> However if I use a joinWindow with *before = time-difference and after = 0*
> on a kstream-kstream-leftjoin the *after=0* part does not seem to work.
> When using _stream1.leftjoin(stream2, joinWindow)_ with
> {_}joinWindow{_}.{_}after=0 and joinWindow.before=30s{_}, any new message on
> stream 1 that can not be joined with any messages on stream2 should be joined
> with a null-record after the _joinWindow.after_ has ended and a new message
> has arrived on stream1.
> It does not.
> Only if the new message arrives after the value of _joinWindow.before_ the
> previous message will be joined with a null-record.
>
> Attached you can find two files with a TopologyTestDriver Unit test to
> reproduce.
> topology: stream1.leftjoin( stream2, joiner, joinwindow)
> joinWindow has before=5000ms and after=0
> message1(key1) -> stream1
> after 4000ms message2(key2) -> stream1 -> NO null-record join was made, but
> the after period was expired.
> after 4900ms message2(key2) -> stream1 -> NO null-record join was made, but
> the after period was expired.
> after 5000ms message2(key2) -> stream1 -> A null-record join was made,
> before period was expired.
> after 6000ms message2(key2) -> stream1 -> A null-record join was made,
> before period was expired.
>
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