org.apache.beam.sdk.transforms

Annotation Type DoFn.TimerId

@Documented
 @Retention(value=RUNTIME)
 @Target(value={FIELD,PARAMETER})
 @Experimental(value=TIMERS)
public static @interface DoFn.TimerId

Annotation for declaring and dereferencing timers.

To declare a timer, create a field of type TimerSpec annotated with a DoFn.TimerId. To use the cell during processing, add a parameter of the type Timer to your @ProcessElement or @OnTimer method, and annotate it with DoFn.TimerId. See the following code for an example:

 new DoFn<KV<Key, Foo>, Baz>() {
    @TimerId("my-timer-id")
    private final TimerSpec myTimer = TimerSpecs.timerForDomain(TimeDomain.EVENT_TIME);

    @ProcessElement
    public void processElement(
        @Element InputT element,
        @TimerId("my-timer-id") Timer myTimer) {
      myTimer.offset(Duration.standardSeconds(...)).setRelative();
    }

    @OnTimer("my-timer-id")
    public void onMyTimer() {
      ...
    }
 }

Timers are subject to the following validity conditions:

• Each timer must have a distinct id.
• Any timer referenced in a parameter must be declared.
• Timer declarations must be final.
• All declared timers must have a corresponding callback annotated with @OnTimer.

Required Element Summary

Required Elements

Modifier and Type	Required Element and Description
java.lang.String	value The timer ID.

Element Detail

value

public abstract java.lang.String value

The timer ID.