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From "Kostas Kloudas (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-6205) Put late elements in side output.
Date Tue, 28 Mar 2017 12:10:41 GMT
Kostas Kloudas created FLINK-6205:
-------------------------------------

             Summary: Put late elements in side output.
                 Key: FLINK-6205
                 URL: https://issues.apache.org/jira/browse/FLINK-6205
             Project: Flink
          Issue Type: Bug
          Components: CEP
    Affects Versions: 1.3.0
            Reporter: Kostas Kloudas
            Assignee: Kostas Kloudas
             Fix For: 1.3.0


Currently the CEP library had a somehow fuzzy way to handle late events. Essentially:
1) it accepts all events (late and early)
2) it sorts them based on event time
3) whenever a watermark arrives, it feeds them into the NFA.

This does not respecting event time.

In addition, given that the order in which elements are processed matters, this could lead
to wrong results as events may be processed by the NFA out-of-order with respect to their
timestamps.

This issue proposes to assume correctness of the watermark and consider as late, events that
arrive having  a timestamp smaller than that of the last seen watermark. In addition, late
events are not silently dropped, but the user can specify to send them to a side output, as
done in the case of the {{WindowOperator}}.



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