Hi Averell, I'd go with approach 2). As of Flink 1.6.0 you can delete timers.
But even if you are on a pre-1.6 version, a ProcessFunction would be the way to go, IMO. You don't need to register a timer for each event. Instead, you can register the first timer with the first event and have a state that is updated with the timestamp of the last seen event. When the timer fires, you check the if you need to raise an alert and register a new timer such that it fires 1 minute after the last seen event (last-seen + 1 minute - (now - last-seen)). Best, Fabian Am Do., 4. Okt. 2018 um 16:15 Uhr schrieb Averell <lvhu...@gmail.com>: > Hi everyone, > > I have a keyed stream which is expecting events every fixed interval (let's > say 1 minute). I want to raise alarms for any key which has received no > events in n-periods. What should be the cheapest way (in term of > performance > ) to do this? > I thought of some solutions, but don't know which one is the best: > 1. Sliding window then count the number of events in each window <<< this > seems quite expensive when n is big. > 2. Register a timer for every single event, record the last event timestamp > and check that timestamp when the timer expires. (This would be the best if > there's an option to cancel/modify a timer, but it seems that feature is > not > available yet) > 3. Session window: i haven't implemented this to verify its feasibility. > Thinking of firing the alarm on every window clear event. > 4. CEP. I don't know whether it's possible or not. Haven't found a guide > for > defining patterns of missing events. > > Could you please give some advices? > > Thanks and best regards, > Averell > > > > -- > Sent from: > http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/ >
