[jira] [Commented] (FLINK-3674) Add an interface for Time aware User Functions

["Aljoscha Krettek (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-3674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15525561#comment-15525561 ] 

Aljoscha Krettek commented on FLINK-3674:
-----------------------------------------

I want to implement this using two new interfaces:
 - {{TimelyFunction}}, this would be implemented by a user function that needs to deal with timers/time
 - {{TimerService}}, this allows so set processing-time/event-time timers and query the current time

{code}
/**
 * Interface for user functions that allows them to deal with time.
 *
 * <p>{@link #setTimerService(TimerService)} is called by the system to provide the function
 * with a {@link TimerService} that can be used to query the current time and set timers.
 *
 * <p>{@link #onTimer(long, TimeDomain)} is called when timers fire.
 */
@PublicEvolving
public interface TimelyFunction {

	/**
	 * Provides a {@link TimerService} to the function.
	 */
	void setTimerService(TimerService timerService);

	/**
	 * Called when a timer set using {@link TimerService} fires.
	 */
	void onTimer(long timestamp, TimeDomain timeDomain);
}

/**
 * Interface for working with time and timers.
 */
@PublicEvolving
public interface TimerService {

	/** Returns the current processing time. */
	long currentProcessingTime();

	/** Returns the current event time. */
	long currentEventTime();

	/**
	 * Registers a timer to be fired when processing time passes the given time.
	 *
	 * <p>Timers can internally be scoped to keys and/or windows. When you set a timer
	 * in a keyed context, such as in an operation on
	 * {@link org.apache.flink.streaming.api.datastream.KeyedStream} then that context
	 * will also be active when you receive the timer notification.
	 */
	void registerProcessingTimeTimer(long time);

	/**
	 * Deletes the given timer in the current key/window scope.
	 */
	void deleteProcessingTimeTimer(long time);

	/**
	 * Registers a timer to be fired when the event time watermark passes the given time.
	 *
	 * <p>Timers can internally be scoped to keys and/or windows. When you set a timer
	 * in a keyed context, such as in an operation on
	 * {@link org.apache.flink.streaming.api.datastream.KeyedStream} then that context
	 * will also be active when you receive the timer notification.
	 */
	void registerEventTimeTimer(long time);

	/**
	 * Deletes the given timer in the current key/window scope.
	 */
	void deleteEventTimeTimer(long time);
}

{code}

I put in the delete methods for now but they will probably go away in the final implementation because deletes cannot be done in an efficient way.

> Add an interface for Time aware User Functions
> ----------------------------------------------
>
>                 Key: FLINK-3674
>                 URL: https://issues.apache.org/jira/browse/FLINK-3674
>             Project: Flink
>          Issue Type: New Feature
>          Components: Streaming
>    Affects Versions: 1.0.0
>            Reporter: Stephan Ewen
>            Assignee: Aljoscha Krettek
>
> I suggest to add an interface that UDFs can implement, which will let them be notified upon watermark updates.
> Example usage:
> {code}
> public interface EventTimeFunction {
>     void onWatermark(Watermark watermark);
> }
> public class MyMapper implements MapFunction<String, String>, EventTimeFunction {
>     private long currentEventTime = Long.MIN_VALUE;
>     public String map(String value) {
>         return value + " @ " + currentEventTime;
>     }
>     public void onWatermark(Watermark watermark) {
>         currentEventTime = watermark.getTimestamp();
>     }
> }
> {code}



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