Hi, You're right, expect that ("grace", "arctic", 25) is emitted with timestamp 90 seconds along with a for watermark 90 seconds.
I followed your advice and implemented a simple window function printing the start + end of a window along with it's content. You can see that a window from minute 1 till 6 is emitted containing the ("grace", "arctic", 25) triple. window: -4 -> 1 key: (arctic) (susi,arctic,20) =================== window: -4 -> 1 key: (elephant) (hans,elephant,15) (pete,elephant,40) =================== window: 1 -> 6 key: (arctic) (grace,arctic,25) =================== window: 0 -> 5 key: (elephant) (hans,elephant,15) (pete,elephant,40) =================== window: 0 -> 5 key: (arctic) (susi,arctic,20) (grace,arctic,25) =================== window: -1 -> 4 key: (arctic) (susi,arctic,20) (grace,arctic,25) =================== window: -1 -> 4 key: (elephant) (hans,elephant,15) (pete,elephant,40) =================== window: -2 -> 3 key: (arctic) (susi,arctic,20) (grace,arctic,25) =================== window: -2 -> 3 key: (elephant) (hans,elephant,15) (pete,elephant,40) =================== window: -3 -> 2 key: (arctic) (susi,arctic,20) (grace,arctic,25) =================== window: -3 -> 2 key: (elephant) (hans,elephant,15) (pete,elephant,40) =================== So what basically happens is that the windowing mechanism emits all unfinished windows when it's closed? Because based on the watermarks Flink can not decide that, the window 1 -> 6 is finished. Best Alex. -- View this message in context: http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Trying-to-comprehend-rolling-windows-event-time-tp5034p5055.html Sent from the Apache Flink User Mailing List archive. mailing list archive at Nabble.com.