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From Ahmad Hassan <ahmad.has...@gmail.com>
Subject Re: Keyed windows with single sink
Date Thu, 22 Jun 2017 14:44:02 GMT
Hi Stefan,

How process function would know that the last window result has arrived?
Because slidingwindows slide every 5 minutes which means that window of new
time-range or new watermark will arrive after 5 minutes.


On 22 June 2017 at 15:10, Stefan Richter <s.richter@data-artisans.com>

> The process function has the signature
> void processElement(I value, Context ctx, Collector<O> out) throws Exception
> where the context is providing access to the current watermark and you can
> also register timer callbacks, when that trigger when a certain watermark
> is reached. You can simply monitor the watermark through the context for
> each incoming window result. *Start* time is not important, because you
> know that you have collected the results for all windows with a smaller
> *end* time than the watermark that you currently see in the context,
> because this is Flinkā€™s notion of completeness. This means you can prepare
> those windows and aggregate results and send them downstream to the sink.
> Am 22.06.2017 um 15:46 schrieb Ahmad Hassan <ahmad.hassan@gmail.com>:
> Thanks Stefan, But how the Process function will have these watermarks? I
> have sliding windows like below
> final DataStream<WindowStats> eventStream = inputStream
> .window(SlidingProcessingTimeWindows.of(Time.minutes(100,Time.minutes(5)))
> .fold(new WindowStats(), new ProductAggregationMapper(), new
> ProductAggregationWindowFunction());
> Window results are coming every 5 minutes after first window output. How
> the process function would know that all the windows for a Tenant have
> finished for a giving start and end time.
> Thanks for help.
> Cheers,
> On 22 June 2017 at 14:37, Stefan Richter <s.richter@data-artisans.com>
> wrote:
>> Hi,
>> one possible approach could be that you have a process function before
>> the sink. Process function is aware of watermarks, so it can collect and
>> buffer window results until it sees a watermark. This is the signal that
>> all results for windows with an end time smaller than the watermark are
>> complete. They can then be aggregated and send to the sink.
>> Best,
>> Stefan
>> > Am 22.06.2017 um 15:15 schrieb Ahmad Hassan <ahmad.hassan@gmail.com>:
>> >
>> > Hi All,
>> >
>> > I am using categoryID as a keyby attribute for creating keyed stream
>> from a product event stream. Keyed stream then creates time windows for
>> each category. However, when the window time expires, i want to write the
>> output data of all the products in all all categories in a single atomic
>> operation collectively. Is there a way to call a single sink function for
>> all the windows with same start and end time. Or is there a way in flink to
>> know that all windows with same end time have finished processing their
>> sink function?
>> >
>> > Currently, each window calls sink function individually.
>> >
>> > cheers,
>> >

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