Hi Till, thank you for your reply. This is exactly what I was looking for!
Flink continues to surprise me with its versatility. :) Best Regards, Julian 2016-11-07 16:47 GMT+01:00 Till Rohrmann <trohrm...@apache.org>: > Hi Julian, > > you can use the TriggerContext to register and unregister event time > timers which fire when the given event time has been passed. That’s one way > to implement what you’ve described. If you don’t want to use time windows > you could also use session windows. Take a look at the > EventTimeSessionWindows class. In order to only obtain the last element, > you should use an Evictor which evicts all elements except for the last. > > Concerning the purging: Time windows are automatically cleaned up after > the end of the window + an allowed lateness. That’s why the trigger no > longer has to take core of that. > > Cheers, > Till > > > On Mon, Nov 7, 2016 at 11:34 AM, Julian Bauß <julian.ba...@gmail.com> > wrote: > >> Hello everybody, >> >> I'm currently trying to implement a Function that allows me to detect >> that a certain amount of time has passed after receiving the last element >> of a stream (in a given time window). For example if nothing happened for 6 >> hours within a given Session I want to do something (set a flag, clear some >> state). >> >> I thought I could solve this with a custom trigger on EventTime >> TimeWindows. I'm currently confused about how I should implement that >> Trigger. The implementation should not be much different from a >> EventTimeTrigger except that it discards of any windows with more than one >> element. This would lead to a windowing mechanism that effectively only >> fires a window after a certain time for the last element. >> >> What I don't understand is when the regular EventTimeTrigger purges >> windows because it only ever returns FIRE and CONTINUE events. >> >> I assumed that after firing a window onEventTime the window would get >> purged eventually. I then would've added a PURGE once the number of >> elements was greater than 1. >> >> Would that be a suitable implementation? >> >> Best Regards, >> >> Julian >> > >
