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From Xingcan Cui <xingc...@gmail.com>
Subject Re: Generate watermarks per key in a KeyedStream
Date Wed, 08 Nov 2017 17:12:02 GMT
Hi Shailesh,

actually, the watermarks are generated per partition, but all of them will
be forcibly aligned to the minimum one during processing. That is decided
by the semantics of watermark and KeyedStream, i.e., the watermarks belong
to a whole stream and a stream is made up of different partitions (one per

If the physical devices work in different time systems due to delay, the
event streams from them should be treated separately.

Hope that helps.


On Wed, Nov 8, 2017 at 11:48 PM, Shailesh Jain <shailesh.jain@stellapps.com>

> Hi,
> I'm working on implementing a use case wherein different physical devices
> are sending events, and due to network/power issues, there can be a delay
> in receiving events at Flink source. One of the operators within the flink
> job is the Pattern operator, and there are certain patterns which are time
> sensitive, so I'm using Event time characteristic. But the problem comes
> when there are unpredictable delays in events from a particular device(s),
> which causes those events to be dropped (as I cannot really define a static
> bound to allow for lateness).
> Since I'm using a KeyedStream, keyed on the source device ID, is there a
> way to allow each CEP operator instance (one per key) to progress its time
> based on the event time in the corresponding stream partition. Or in other
> words, is there a way to generate watermarks per partition in a KeyedStream?
> Thanks,
> Shailesh

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