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From Aljoscha Krettek <aljos...@apache.org>
Subject Re: Event time, watermarks and windows
Date Mon, 24 Oct 2016 17:38:21 GMT
the call to setAutoWatermarkInterval() is still necessary to activate the
watermark-generation mechanism. However, calling
setStreamTimeCharacteristic(EventTime) will also set a good default value
for the auto watermark interval.


On Mon, 24 Oct 2016 at 17:02 Paul Joireman <paul.joireman@physiq.com> wrote:

> Hi all,
> The  event timestamp and watermarks documentation (v. 1.1)
> https://ci.apache.org/projects/flink/flink-docs-release-1.1/apis/streaming/event_timestamps_watermarks.html
> that
>      The AssignerWithPeriodicWatermarks assigns timestamps and generates
> watermarks periodically (possibly depending on the stream elements, or
> purely
>       based on processing time).
>      The interval (every n milliseconds) in which the watermark will be
> generated is defined via ExecutionConfig.setAutoWatermarkInterval(...).
> Each time, the
>      assigner’s getCurrentWatermark() method will be called, and a new
> Watermark will be emitted, if the returned Watermark is non-null and larger
> than the
>       previous Watermark.
> It goes on to give an example of the
> BoundedOutOfOrdernessTimestampExtractor.   My question is that since the BoundedOutOfOrdernessTimestampExtractor
> is a sub-class of the AssignerWithPeriodicWatermarks is it necessary to
> call ExecutionConfig.setAutoWatermarkInterval(...) on the environment in
> order to actually generate watermarks or should they be generated
> "automatically" by the subsequent operators.
> In other words, will an event time window still fire if this call
> (setAutoWatermarkInterval) is not present?
> Regards,
> Paul W Joireman

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