Assigning timestamps and watermarks several times, several datastreams?

[Aakarsh Madhavan]

Hi!

Currently I am using Flink 1.4.2.

class TSWM implements AssignerWithPunctuatedWatermarks<POJO> {
   long maxTS = Long.MIN_VALUE;
   @Override
  public Watermark checkAndGetNextWatermark(POJO event, long l) {
    maxTS = Math.max(maxTS, event.TS);
    return new Watermark(getMaxTimestamp());
  }

  @Override
  public long extractTimestamp(POJO event, long l) {
    maxTS = Math.max(maxTS, event.TS);
    return event.TS;
  }
}

DataStream<POJO> ds1 = ... .assignTimestampsAndWatermarks(new TSWM())

DataStream<POJO> ds2 = ... .assignTimestampsAndWatermarks(new TSWM())
Suppose I ran this code above, what I am confused about is the overall
watermarking system.

Now I want to do the following:

ds1.keyBy("id").window(SlidingEventTimeWindows.of(Time.minutes(1),
Time.seconds(30))).trigger(EventTimeTrigger.create()).apply(someApplyFunction);

ds2.keyBy("id").window(SlidingEventTimeWindows.of(Time.minutes(1),
Time.seconds(30))).trigger(EventTimeTrigger.create()).apply(someApplyFunction);

The main doubt I am having is how this works with the watermarks. Does
`ds1` and `ds2` have separate watermarks that don't concern each other? Ie
do they operate separately?

I am just not sure how the window trigger would work for example or how the
watermarks would advance. Do they watermarks reset and advance for each
stream separately so no data is lost?

Thanks!