Apache Flink: No output when using event time with multiple Kafka partitions

Question

I am reading messages from a Kafka topic with 2 partitions and using event time. This is my code:

stream.assignTimestampsAndWatermarks(new AscendingTimestampExtractor<Request>() {
    @Override
    public long extractAscendingTimestamp(Request req) {
        return req.ts;
    }
})
.windowAll(TumblingEventTimeWindows.of(Time.days(1)))
.apply((TimeWindow window, Iterable<Request> iterable, Collector<String> collector) -> {
    collector.collect("Window: " + window.toString());
    for (Request req : iterable) {
        collector.collect(req.toString());
    }
})
.print()

I could get an output only when setting the Kafka source parallelism to 1. According to this thread , I guess that is because messages from multiple partitions arrive out-of-order to the timestamp extractor.

So I replaced the AscendingTimestampExtractor with a BoundedOutOfOrdernessGenerator as in this documentation example (with a higher maxOutOfOrderness delay), in order to handle out-of-order events, but I still can't get any output. Why is that?

Answer 1

Check that the event timestamp is OK. Must have a 13 length to be used in Flink Java Epoch.

Correct : 1563743505673

Incorrect : 1563743505

Ref.: https://ci.apache.org/projects/flink/flink-docs-stable/dev/event_timestamps_watermarks.html#assigning-timestamps