+1 Etienne
Le 28/03/2017 à 22:27, Kenneth Knowles a écrit :
Hi all, I have a little extension to the stateful DoFn annotations to circulate for feedback: Allow a method to be annotated with @OnWindowExpiration to automatically get a callback at some point after the window has expired, but before the state for the window has been cleared. Today, a user can pretty easily get the same effect by setting a timer for the end of the window + allowed lateness in their @ProcessElement calls. But having just one annotation for it has a couple nice benefits: 1. Some users assume a naive implementation so they are concerned that setting a timer repeatedly is costly. This eliminates the cause for user alarm and allows a runner to do a better job in case it didn't already do it efficiently. 2. Getting the allowed lateness to be available to your @ProcessElement is a little crufty. 3. Often, if you don't have @OnWindowExpiration, you are leaving behind state that might contain data that is otherwise lost. So I would even consider making it mandatory (with some way of indicating state you don't care about dropping) though that could be annoying. Another interesting moment in a window's lifecycle is @EndOfWindow. This is not critical for correctness, though. Thoughts? Kenn
