Github user StephanEwen commented on the pull request:
https://github.com/apache/flink/pull/1764#issuecomment-195489648
I think this is a useful tool. Few comments, though:
- You can still have a negative underflow (wrap around, positive) in the
watermark generation.
- We have somehow reached the conclusion to use Guava as little as
possible, potentially getting rid of it in the future.
- If the `extractWatermark(T, long)` and `getCurrentWatermark()` method
should not be overridden, they should probably be final.
### About the name
I am not sure about the name, maybe a native speaker can chime in here. My
git feeling was that this "trailing" would be understood as "event time trails
by a certain amount behind processing time".
I used the term "max out of orderness" in the example in the documentation
for the same case solved here:
https://ci.apache.org/projects/flink/flink-docs-release-1.0/apis/streaming/event_timestamps_watermarks.html#timestamp-assigners--watermark-generators
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