This is great. Thanks for the contribution Rehman.
On Thu, Jan 23, 2020 at 10:09 AM Reuven Lax <[email protected]> wrote:
> Thanks to a lot of hard work by Rehman, Beam now supports dynamic timers.
> As a reminder, this was discussed on the dev list some time back.
>
> As background, previously one had to statically declare all timers in your
> code. So if you wanted to have two timers, you needed to create two timer
> variables and two callbacks - one for each timer. A number of users kept
> hitting stumbling blocks where they needed a dynamic set of timers (often
> based on the element), which was not supported in Beam. The workarounds
> were quite ugly and complicated.
>
> The new support allows declaring a TimerMap, which is a map of timers.
> Each TimerMap is scoped by a family name, so you can create multiple
> TimerMaps each with its own callback. The use looks as follows:
>
> class MyDoFn extends DoFn<...> {
> @TimerFamily("timers")
> private final TimerSpec timerMap =
> TimerSpecs.timerMap(TimeDomain.EVENT_TIME);
>
> @ProcessElement
> public void process(@TimerFamily("timers") TimerMap timers, @Element
> Type e) {
> timers.set("mainTimer", timestamp);
> timers.set("actionType" + e.getActionType(), timestamp);
> }
>
> @OnTimerFamily .
> public void onTimer(@TimerId String timerId) {
> System.out.println("Timer fired. id: " + timerId);
> }
> }
>
> This currently works for the Flink and the Dataflow runners.
>
> Thank you Rehman for getting this done! Beam users will find it very
> valuable.
>
> Reuven
>
