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From "Hamilton, Paul" <paul.hamilto...@sap.com>
Subject Session Based Windows
Date Fri, 16 Oct 2015 17:36:22 GMT

I am attempting to make use of the new window APIs in streaming to
implement a session based window and am not sure if the currently provided
functionality handles my use case.  Specifically what I want to do is
something conceptually similar to a ³Sessions.withGapDuration(Š)² window
in Google DataFlow.

Assuming the events are keyed by session id.  I would like to use the
event time and the watermarking functionality to trigger a window after
the ³end of a session² (no events for a given session received within x
amount of time).  With watermarking this would mean trigger when a
watermark is seen that is > (the time of the last event + session
timeout). Also I want to perform an early triggering of the window after a
given number of events have been received.

Is it currently possible to do this with the current combination of window
assigners and triggers?  I am happy to write custom triggers etc, but
wanted to make sure it wasn¹t already available before going down that


Paul Hamilton
Hybris Software

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