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From Paul Joireman <paul.joire...@physiq.com>
Subject Event time, watermarks and windows
Date Mon, 24 Oct 2016 15:02:16 GMT
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
states 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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