org.apache.samza.operators.functions

Interface ScheduledFunction<K,OM>

Type Parameters:

K - type of the key

OM - type of the output

public interface ScheduledFunction<K,OM>

Allows scheduling a callback for a specific epoch-time. Key must be a unique identifier for its corresponding logic to execute, and is provided in the callback when the corresponding schedule time occurs.

Example of a FlatMapFunction with ScheduledFunction:

    public class ExampleScheduledFn implements FlatMapFunction<String, String>, ScheduledFunction<String, String> {
      // for recurring callbacks, keep track of the scheduler from "schedule"
      private Scheduler scheduler;

      public void schedule(Scheduler scheduler) {
        // save the scheduler for recurring callbacks
        this.scheduler = scheduler;
        long time = System.currentTimeMillis() + 5000; // fire after 5 sec
        scheduler.schedule("do-delayed-logic", time);
      }
      public Collection<String> apply(String s) {
        ...
      }
      public Collection<String> onCallback(String key, long timestamp) {
        // do some logic for key "do-delayed-logic"
        ...
        // for recurring callbacks, call the saved scheduler again
        this.scheduler.schedule("example-process", System.currentTimeMillis() + 5000);
      }
    }
 

Method Summary

Modifier and Type	Method and Description
java.util.Collection<OM>	onCallback(K key, long timestamp) Returns the output from the scheduling logic corresponding to the key that was triggered.
void	schedule(Scheduler<K> scheduler) Allows scheduling the initial callback(s) and saving the scheduler for later use for recurring callbacks.

Method Detail

schedule

void schedule(Scheduler<K> scheduler)

Allows scheduling the initial callback(s) and saving the scheduler for later use for recurring callbacks.

Parameters:

scheduler - used to specify the schedule time(s) and key(s)

onCallback

java.util.Collection<OM> onCallback(K key,
                                    long timestamp)

Returns the output from the scheduling logic corresponding to the key that was triggered.

Parameters:

key - key corresponding to the callback that got invoked

timestamp - schedule time that was set for the callback for the key, in milliseconds since epoch

Returns:

Collection of output elements