WatermarkPolicy (hazelcast-jet-all 0.6 API)

```
public interface WatermarkPolicy
```
This object runs inside a Jet processor, inspects the event timestamps as they occur in the input and and decides on the current value of the watermark. It controls how much disorder Jet will allow in a data stream and which events will be marked as "too late" and dropped. It also decides what to do with the watermark when there are no events for a while. If just one of the many processors working in parallel doesn't receive any events, its watermark may fall behind and impede the progress of the entire DAG. The policy may decide to advance the watermark based on the passage of time alone.
The processor must report to this object the timestamp of every event it receives by calling reportEvent(long). It must also ensure that, even in the absence of events, it keeps checking the current value of the watermark. When the watermark advances far enough (as decided by the WatermarkEmissionPolicy, if in use), it must emit a watermark item to its output edges.

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`long`	`getCurrentWatermark()` Called to get the current watermark in the absence of an observed event.
`long`	`reportEvent(long timestamp)` Called to report the observation of an event with the given timestamp.

Interface WatermarkPolicy