Window operators drop late events by default. When they receive a late event, they already computed and emitted a result.
Since there is not good default behavior to hay ndle a late event in this case, they are simply dropped.
However, Flink offers multiple ways to explicitly handle late events such as sending them to a side output or computing and emitting an updated result.

So, if you apply a ProcessFunction before any other operator, you can handle all late events.

Best, Fabian

2018-04-04 23:26 GMT+02:00 shishal <>:
Thanks Fabian, My understand was that late event older than watermark is
dropped. So processFunction wont be called for late event. So I guess my
understanding was wrong. Or there is something more to it?