[jira] [Created] (FLINK-3428) Add fixed time trailing timestamp/watermark extractor

[Shang Yuanchun (Jira)]

Robert Metzger created FLINK-3428:
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             Summary: Add fixed time trailing timestamp/watermark extractor
                 Key: FLINK-3428
                 URL: https://issues.apache.org/jira/browse/FLINK-3428
             Project: Flink
          Issue Type: Improvement
            Reporter: Robert Metzger


Flink currently provides only one build-in timestamp extractor, which assumes strictly ascending timestamps. In real world use cases, timestamps are almost never strictly ascending.

Therefore, I propose to provide an utility watermark extractor which is generating watermarks with a fixed-time trailing.

The implementation should keep track of the highest event-time seen so far and subtract a fixed amount of time from that event time.

This way, users can for example specify that the watermarks should always "lag behind" 10 minutes.



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