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From Igor Berman <igor.ber...@gmail.com>
Subject Re: Event processing time with lateness
Date Fri, 03 Jun 2016 14:40:26 GMT
thanks Kosta

On 3 June 2016 at 16:47, Kostas Kloudas <k.kloudas@data-artisans.com> wrote:

> Hi Igor,
>
> To handle late events in Flink you would have to implement you own custom
> trigger.
>
> To see a relatively more complex example of such a trigger and how to
> implement it,
> you can have a look at this implementation:
> https://github.com/dataArtisans/beam_comp/blob/master/src/main/java/com/dataartisans/beam_comparison/customTriggers/EventTimeTriggerWithEarlyAndLateFiring.java
>
> Which implements the trigger described in this article (before the
> conclusions section)
> http://data-artisans.com/why-apache-beam/
>
> Thanks,
> Kostas
>
> On Jun 3, 2016, at 2:55 PM, Igor Berman <igor.berman@gmail.com> wrote:
>
> Hi
>
> according to presentation of Tyler Akidau
> https://docs.google.com/presentation/d/13YZy2trPugC8Zr9M8_TfSApSCZBGUDZdzi-WUz95JJw/present
Flink
> supports late arrivals for window processing, while I've seen several
> question in the userlist regarding late arrivals and answer was - sort of
> "not for all usecases"
> Can somebody clarify?
>
> The interesting case for me - I have event processing time, while I want
> to aggregate by tumbling window. The events come from kafka and might be
> late. Currently we define lateness threshold with watermark (e.g. 5 mins)
>
> After window triggers I want to save aggregated result at some persistent
> storage(redis/hbase) with start timestamp of window
>
> After this grace period - if I understand correctly - any event won't be
> aggregated into existing window, but rather the trigger will call
> aggregated function with only 1 element inside(the late one)
>
> so if my window method saves into persistent storage - it will override
> aggregated result with new one that has only 1 element inside
>
> what I want to achieve - is that late arrival will trigger window method
> with all elements (late + all other) so that aggregated result will be
> complete
>
> you can think about use case of page visits counts per minute, while due
> to some problems page visit events might arrive late
>
> thanks in advance
>
>
>
>

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