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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-8384) Session Window Assigner with Dynamic Gaps
Date Wed, 31 Jan 2018 15:19:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-8384?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16346996#comment-16346996
] 

ASF GitHub Bot commented on FLINK-8384:
---------------------------------------

Github user aljoscha commented on the issue:

    https://github.com/apache/flink/pull/5295
  
    Yes, that was me. 😅 It was just a quick idea, and it would work because both `withGap()`
and `withGapExtractor()` are static so the latter could have `T` on the method signature and
return a `DynamicEventTimeSessionWindows` (or some such). I'm not against keeping it in the
separate class, though.
    
    I agree that the cast is a bit wonky but we know that it always works because the trigger
we return never looks at the element.


> Session Window Assigner with Dynamic Gaps
> -----------------------------------------
>
>                 Key: FLINK-8384
>                 URL: https://issues.apache.org/jira/browse/FLINK-8384
>             Project: Flink
>          Issue Type: Improvement
>          Components: Streaming
>            Reporter: Dyana Rose
>            Priority: Minor
>
> *Reason for Improvement*
> Currently both Session Window assigners only allow a static inactivity gap. 
> Given the following scenario, this is too restrictive:
> * Given a stream of IoT events from many device types
> * Assume each device type could have a different inactivity gap
> * Assume each device type gap could change while sessions are in flight
> By allowing dynamic inactivity gaps, the correct gap can be determined in the [assignWindows
function|https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/windowing/assigners/EventTimeSessionWindows.java#L59]
by passing the element currently under consideration, the timestamp, and the context to a
user defined function. This eliminates the need to create unwieldy work arounds if you only
have static gaps.
> Dynamic Session Window gaps should be available for both Event Time and Processing Time
streams.
> (short preliminary discussion: https://lists.apache.org/thread.html/08a011c0039e826343e9be0b1bb4e0000cfc2e12976bc65f8a43ee88@%3Cdev.flink.apache.org%3E)



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