org.apache.flink.api.common.eventtime

Interface WatermarkGenerator<T>

All Known Implementing Classes:

AscendingTimestampsWatermarks, AssignerWithPeriodicWatermarksAdapter, AssignerWithPunctuatedWatermarksAdapter, BoundedOutOfOrdernessWatermarks, GeneratedWatermarkGeneratorSupplier.DefaultWatermarkGenerator, NoWatermarksGenerator, WatermarksWithIdleness

@Public
public interface WatermarkGenerator<T>

The WatermarkGenerator generates watermarks either based on events or periodically (in a fixed interval).

Note: This WatermarkGenerator subsumes the previous distinction between the AssignerWithPunctuatedWatermarks and the AssignerWithPeriodicWatermarks.

Method Summary

Modifier and Type	Method and Description
void	onEvent(T event, long eventTimestamp, WatermarkOutput output) Called for every event, allows the watermark generator to examine and remember the event timestamps, or to emit a watermark based on the event itself.
void	onPeriodicEmit(WatermarkOutput output) Called periodically, and might emit a new watermark, or not.

Method Detail

onEvent

void onEvent(T event,
             long eventTimestamp,
             WatermarkOutput output)

Called for every event, allows the watermark generator to examine and remember the event timestamps, or to emit a watermark based on the event itself.

onPeriodicEmit

void onPeriodicEmit(WatermarkOutput output)

Called periodically, and might emit a new watermark, or not.

The interval in which this method is called and Watermarks are generated depends on ExecutionConfig.getAutoWatermarkInterval().