Hi Chirag, I agree it might be a little bit confusing.
Let me try to explain the reasoning. To do that I'll first try to rephrase the reasoning from FLINK-8560 for introducing the KeyedProcessFunction. It was introduced so that users have a typed access to the current key via Context and OnTimerContext. This is actually the only difference between the two function. Somewhat as a consequence of the above, the KeyedProcessFunction can be used solely on a keyed stream, however ProcessFunction can be used in both. That was actually the only way to use a ProcessFunction on a keyed stream prior to introducing the KeyedProcessFunction. If you don't need access to the current key you should be fine with using the ProcessFunction on a keyed stream and there you can use the TimerService. It is advised to use a KeyedProcessFunction on a keyed stream, however for backwards compatibility the old behaviour has been kept. Hope that it clarifies the things a bit. Best, Dawid On 17/03/2021 07:47, Chirag Dewan wrote: > Hi, > > Currently, both ProcessFunction and KeyedProcessFunction (and their > CoProcess counterparts) expose the Context and TimerService in the > processElement() method. However, if we use the TimerService in non > keyed context, it gives a runtime error. > > I am a bit confused about these APIs. Is there any specific reason for > exposing TimerService in non-keyed context especially if it cant be > used without keyed stream? > > Any leads are much appreciated. > > Thanks, > Chirag
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