Hi Dhruv, I can see it's confusing, and it does seem the comment should be improved. You can find concrete explanation of tumbling window and relative arguments at https://ci.apache.org/projects/flink/flink-docs-master/dev/stream/operators/windows.html#tumbling-windows
Feel free to open a PR with better comment. Thanks, Bowen On Sun, May 27, 2018 at 12:43 PM, Dhruv Kumar <gargdhru...@gmail.com> wrote: > Hi > > I was looking at TumblingProcessingTimeWindows.java > <https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/windowing/assigners/TumblingProcessingTimeWindows.java> > and > was a bit confused with the documentation at the start of this class. It > says the following: > > /** > * A {@link WindowAssigner} that windows elements into windows based on > the current > * system time of the machine the operation is running on. Windows cannot > overlap. > * > * <p>For example, in order to window into windows of 1 minute, every 10 > seconds: > * <pre> {@code > * DataStream<Tuple2<String, Integer>> in = ...; > * KeyedStream<String, Tuple2<String, Integer>> keyed = in.keyBy(...); > * WindowedStream<Tuple2<String, Integer>, String, TimeWindows> windowed = > * keyed.window(TumblingProcessingTimeWindows.of(Time.of(1, MINUTES), > Time.of(10, SECONDS)); > * } </pre> > */ > It says one can have tumbling windows of 1 minute, every 10 seconds. > Doesn’t this become a sliding window then? The SlidingProcessTimeWindows. > java > <https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/windowing/assigners/SlidingProcessingTimeWindows.java> > has > the exact same documentation with just one tiny change (“Windows can > possibly overlap”). It seems to me that in the above documentation, the > second Time argument of 10 seconds is for providing the window offset (as > confirmed here > <https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/windowing/assigners/TumblingProcessingTimeWindows.java#L92>) > and not for starting the tumbling window every 10 seconds. > > Thanks > > > -------------------------------------------------- > *Dhruv Kumar* > PhD Candidate > Department of Computer Science and Engineering > University of Minnesota > www.dhruvkumar.me > >
