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From Till Rohrmann <trohrm...@apache.org>
Subject Re: TimeWindow not getting last elements any longer with flink 1.0 vs 0.10.1
Date Mon, 14 Mar 2016 14:10:35 GMT
Hi Arnaud,

with version 1.0 the behaviour for window triggering in case of a finite
stream was slightly changed. If you use event time, then all unfinished
windows are triggered in case that your stream ends. This can be motivated
by the fact that the end of a stream is equivalent to no elements will
arrive until the maximum time (infinity) has been reached. This knowledge,
allows you to emit a Long.MaxValue watermark when an event time stream is
finished, which will trigger all lingering windows.

In contrast to event time, you cannot say the same about a finished
processing time stream. There we don’t have logical time but the actual
processing time we use to reason about windows. When a stream finishes,
then we cannot fast forward the processing time to a point where the
windows will fire. This can only happen if we keep the operators alive
until the wall clock tells us that it’s time to fire the windows. However,
there is no such feature implemented yet in Flink.

I hope this helps you to understand the failing test cases.

Cheers,
Till
​

On Mon, Mar 14, 2016 at 1:14 PM, LINZ, Arnaud <ALINZ@bouyguestelecom.fr>
wrote:

> Hello,
>
>
>
> I’ve switched my Flink version from 0.10.1 to 1.0 and I have a regression
> in some  of my unit tests.
>
>
>
> To narrow the problem, here is what I’ve figured out:
>
>
>
> -          I use a simple Streaming application with a source defined as
> “fromElements("Element 1", "Element 2", "Element 3")
>
> -          I use a simple time window function with a 3 second window :
> timeWindowAll(Time.seconds(3))
>
> -          I use an apply() function and counts the total number of
> elements I get with a global counter
>
>
>
> With the previous version, I got all three elements because, not because
> they are  triggered under 3 seconds, but because the source ends
>
> With the 1.0 version, I don’t get any elements, and that’s annoying
> because as the source ends the application ends even if I sleep 5 seconds
> after the execute() method.
>
>
>
> (If I replace fromElement with fromCollection with a 10000 element list
> and Time.second(3) with Time.millisecond(1), I get a random number of
> elements)
>
>
>
> Is this behavior wanted ? If yes, how do I get my last elements now ?
>
>
>
> Best regards,
>
> Arnaud
>
>
>
>
>
>
>
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