Thanks for the explanation. -----Original Message----- From: Fabian Hueske [mailto:fhue...@gmail.com] Sent: Thursday, April 27, 2017 3:17 PM To: dev@flink.apache.org Subject: Re: question about rowtime processfunction - are watermarks needed?
Hi Radu, event-time processing requires watermarks. Operators use watermarks to compute the current event-time. The ProcessFunctions for over range windows use the TimerServices to group elements by time. In case of event-time, the timers are triggered by the event-time of the operator which is derived from the received watermarks. In case of processing-time, the timers are triggered based on the wallclock time of the operator. So by using event-tim timers, we implicitly rely on the watermarks because the timers are triggered based on the received watermarks. Best, Fabian 2017-04-27 10:51 GMT+02:00 Radu Tudoran <radu.tudo...@huawei.com>: > Hi, > > I am looking at the implementation of RowTimeBoundedRangeOver (in the > context of Stream SQL). I see that the logic is that the progress > happens based on the timestamps of the rowevent - i.e., when an even > arrives we register to be processed based on it's timestamp (ctx.timerService. > registerEventTimeTimer(triggeringTs)) > > In the onTimer we remove (retract) data that has expired. However, we > do not consider watermarks nor some allowed latency for the events or > anything like this, which makes me ask: > Don't we need to work with watermarks when we deal with even time? And > keep the events within the allowed delayed/next watermark? Am I > missing something? Or maybe we do not consider at this point > allowedLateness for this version? > > Thanks > > Best regards, > >
