Hi Till, Thanks for your answer! You also answered the next question that I was about to ask "Can we share state between a Trigger and a Window?" Currently the only (convoluted) way to share state between two operators is through the broadcast state pattern, right? Also, in your example, why can't we use a ValueStateDescriptor<Boolean> in the Trigger? I tried using it in my own example but it I am not able to call the mergePartitionedState() method on a ValueStateDescriptor.
Regards, Manas On Tue, Feb 18, 2020 at 7:20 PM Till Rohrmann <trohrm...@apache.org> wrote: > Hi Manas, > > you can implement something like this with a bit of trigger magic. What > you need to do is to define your own trigger implementation which keeps > state to remember whether it has triggered the "started window" message or > not. In the stateful window function you would need to do something > similar. The first call could trigger the output of "window started" and > any subsequent call will trigger the evaluation of the window. It would > have been a bit easier if the trigger and the window process function could > share its internal state. Unfortunately, this is not possible at the moment. > > I've drafted a potential solution which you can find here [1]. > > [1] https://gist.github.com/tillrohrmann/5251f6d62e256b60947eea7b553519ef > > Cheers, > Till > > On Mon, Feb 17, 2020 at 8:09 AM Manas Kale <manaskal...@gmail.com> wrote: > >> Hi, >> I want to achieve the following using event time session windows: >> >> 1. When the window.getStart() and last event timestamp in the window >> is greater than MIN_WINDOW_SIZE milliseconds, I want to emit a message >> "Window started @ timestamp". >> 2. When the session window ends, i.e. the watermark passes >> lasteventTimestamp + inactivityPeriod, I want to emit a message "Window >> ended @ timestamp". >> >> It is guaranteed that all events are on time and no lateness is allowed. >> I am having difficulty implementing both 1 and 2 simultaneously. >> I am able to implement point 1 using a custom trigger, which checks if >> (lastEventTimestamp - window.getStart()) > MIN_WINDOW_SIZE and triggers a >> customProcessWindowFunction(). >> However, with this architecture I can't detect the end of the window. >> >> Is my approach correct or is there a completely different method to >> achieve this? >> >> Thanks, >> Manas Kale >> >> >> >>
