WatermarkGenerator (Flink : 2.0-SNAPSHOT API)

All Known Implementing Classes:

AscendingTimestampsWatermarks, 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

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	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().