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From Chang Liu <fluency...@gmail.com>
Subject Re: Question about Window Tigger
Date Tue, 25 Sep 2018 08:35:53 GMT
Hi Rong,

Thanks for your reply. :)

Best regards/祝好,

Chang Liu 刘畅

> On 19 Sep 2018, at 18:20, Rong Rong <walterddr@gmail.com> wrote:
> Hi Chang,
> There were some previous discussion regarding how to debug watermark and window triggers[1].
> Basically if there's no data for some partitions there's no way to advance watermark.
As it would not be able to determine whether this is due to network failure or actually there's
no data arriving at the source.
> I think your use case is better of using SlidingProcessingTimeWindow.
> Thanks,
> Rong
> [1] http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/watermark-does-not-progress-td22315.html
> On Wed, Sep 19, 2018 at 1:48 AM Chang Liu <fluency.03@gmail.com <mailto:fluency.03@gmail.com>>
> Dear All,
> I have a question about the Window Trigger: let’s say i would like like use the SlidingEventTimeWindow
(60 seconds window size + 1 second window shift) to count the number of records per window.
And I am using Event Time with periodic watermarking with certain maxOurOfOrderness time.
> Sometimes, what happens is: during certain time, there is no incoming event, and then
the watermark for triggering the window fire is not coming.  Then, the last several records
will be just stayed in the window.  It will fire only when the window sees the watermark to
> What I would like to achieve is: if there is no just watermark coming within certain
time (maybe this time is system clock time?), I can still trigger the window to fire no matter
whether there is new event coming or not. Then I can still get the window count for this window,
without waiting the next event, which could be coming after a long time.
> Do you have any idea how can I do this? Many Thanks :)
> Best regards/祝好,
> Chang Liu 刘畅

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