Hi, the problem with using session windows is that you don't know which one is the "first element" unless you keep some sort of state in the WindowAssigner, right? Otherwise, the first element could spawn a window and the non-first elements could have windows of length 0 that get merged into the first window of the length that you desired.
Cheers, Aljoschae On Tue, 16 Aug 2016 at 11:54 Ufuk Celebi <u...@apache.org> wrote: > If I'm understanding correctly, you want something liked > "tumbling-session" windows. Session windows [1] do exactly what you > describe but are only evaluated after a certain period of inactivity, > but you want to evaluate the window every X minutes after the first > element for a key arrived, right? I think Gyula (cc'd) did something > similiar for [2]. Maybe he can share his code? > > [1] > https://ci.apache.org/projects/flink/flink-docs-master/apis/streaming/windows.html#session-windows > [2] https://techblog.king.com/rbea-scalable-real-time-analytics-king/ > > On Mon, Aug 15, 2016 at 7:05 PM, dan bress <danbr...@gmail.com> wrote: > > I am interesting in writing a custom tumbling window assigner to do the > > following: > > > > As soon as the first event for that keyed stream comes in, create a > window > > from that point going forward N milli seconds. Is it possible to do that > > using flink? What I want to do is get all events that occurred in a 5 > > minute period, where the period starts with the time of the first event. > > Flink's current tumbling time windows would be locked to the top of 0, 5, > > 10, 15 minutes, which doesn't work well for me if the first event for a > key > > comes in at 14 minutes, because the window will be triggered at 15 > minutes, > > instead of at 19 minutes. > > > > Looking at the interface for WindowAssigner it doesn't look like I have > > enough information to do what I need. > > > > I would need to know the key, since each keyed stream could have a > > different start time, and I would need to be able to store some state > about > > what the start time is for each key, like a Map of > > StreamKey->FirstEventTime. > > > > Do you have any suggestions for assigning a window that starts with the > > time of the first event in that keyed stream, and ends N minutes after > that? > > > > Thanks! > > > > Dan >
