Hi Flink users, I've been spending time to learn and play with Flink DataStream API, not an expert level but as a beginner. :)
To play with custom window API, I just created a small example, session window based on fixed time gap, but indicate the type of event which may contain "end of session". I guess it's not unusual to see this kind of things (like manual logout and login) though I don't have concrete real use case. This is an implementation based on Flink DataStream API: https://gist.github.com/HeartSaVioR/1d865b1a444af1ef7cae201bbdb196b0 Custom window works pretty well and I could leverage side output very easily. One thing leading the code a bit longer was new definition of TimeWindow (to deal with event type of "close session"). Even though I tried to leverage TimeWindow via inheritance, the code goes a bit verbose as I need to implement a new Serializer as well. (Actually it required to implement a new Trigger as well, but took workaround to leverage existing EventTimeTrigger.) Assuming this pattern is not unusual (it would be pretty OK if it's unusual), could someone point out some points to improve or simplify the code? That would be really nice if there's something I could contribute in this case. Thanks, Jungtaek Lim (HeartSaVioR) ps. This is an implementation based on Spark Structured Streaming (no custom window API, so had to put everything in state function of flatMapGroupsWithState): https://gist.github.com/HeartSaVioR/133c3bdc163f1fd5332397c5cd4b8b29
