[jira] [Commented] (KAFKA-4325) Improve processing of late records for window operations

["Jeyhun Karimov (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-4325?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16035688#comment-16035688 ] 

Jeyhun Karimov commented on KAFKA-4325:
---------------------------------------

[~mjsax], would this jira requre KIP? 

> Improve processing of late records for window operations
> --------------------------------------------------------
>
>                 Key: KAFKA-4325
>                 URL: https://issues.apache.org/jira/browse/KAFKA-4325
>             Project: Kafka
>          Issue Type: Improvement
>          Components: streams
>            Reporter: Matthias J. Sax
>            Priority: Minor
>
> Windows are kept until their retention time passed. If a late arriving record is processed that is older than any window kept, a new window is created containing this single late arriving record, the aggregation is computed and the window is immediately discarded afterward (as it is older than retention time).
> This behavior might case problems for downstream application as the original window aggregate might we overwritten with the late single-record- aggregate value. Thus, we should rather not process the late arriving record for this case.
> However, data loss might not be acceptable for all use cases. In order to enable the use to not lose any data, window operators should allow to register a handler function that is called instead of just dropping the late arriving record.



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