[jira] [Created] (KAFKA-12718) SessionWindows are closed too early

["Matthias J. Sax (Jira)" <ji...@apache.org>]

Matthias J. Sax created KAFKA-12718:
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             Summary: 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


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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