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https://issues.apache.org/jira/browse/KAFKA-12718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17356000#comment-17356000
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Guozhang Wang commented on KAFKA-12718:
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Hi folks, I'm bumping up the priority of this ticket for 3.0 for now (note that
we still have plenty of time towards the code freeze:
https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=177046466 but
still would be good to get this easy fix asap).
> SessionWindows are closed too early
> -----------------------------------
>
> Key: KAFKA-12718
> URL: https://issues.apache.org/jira/browse/KAFKA-12718
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Reporter: Matthias J. Sax
> Assignee: Juan C. Gonzalez-Zurita
> Priority: Critical
> Labels: beginner, easy-fix, newbie
> Fix For: 3.0.0
>
>
> SessionWindows are defined based on a {{gap}} parameter, and also support an
> additional {{grace-period}} configuration to handle out-of-order data.
> To incorporate the session-gap a session window should only be closed at
> {{window-end + gap}} and to incorporate grace-period, the close time should
> be pushed out further to {{window-end + gap + grace}}.
> However, atm we compute the window close time as {{window-end + grace}}
> omitting the {{gap}} parameter.
> Because default grace-period is 24h most users might not notice this issues.
> Even if they set a grace period explicitly (eg, when using suppress()), they
> would most likely set a grace-period larger than gap-time not hitting the
> issue (or maybe only realize it when inspecting the behavior closely).
> However, if a user wants to disable the grace-period and sets it to zero (on
> any other value smaller than gap-time), sessions might be close too early and
> user might notice.
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