Watermark (Flink : 2.0-preview1 API)

java.lang.Object
- org.apache.flink.streaming.runtime.streamrecord.StreamElement
- - org.apache.flink.streaming.api.watermark.Watermark

Direct Known Subclasses:

InternalWatermark
```
@PublicEvolving
public class Watermark
extends StreamElement
```
A Watermark tells operators that no elements with a timestamp older or equal to the watermark timestamp should arrive at the operator. Watermarks are emitted at the sources and propagate through the operators of the topology. Operators must themselves emit watermarks to downstream operators using Output.emitWatermark(Watermark). Operators that do not internally buffer elements can always forward the watermark that they receive. Operators that buffer elements, such as window operators, must forward a watermark after emission of elements that is triggered by the arriving watermark.
In some cases a watermark is only a heuristic and operators should be able to deal with late elements. They can either discard those or update the result and emit updates/retractions to downstream operations.
When a source closes it will emit a final watermark with timestamp Long.MAX_VALUE. When an operator receives this it will know that no more input will be arriving in the future.

Field Summary

Fields
Modifier and Type	Field	Description
`static Watermark`	`MAX_WATERMARK`	The watermark that signifies end-of-event-time.
`protected long`	`timestamp`	The timestamp of the watermark in milliseconds.
`static Watermark`	`UNINITIALIZED`	The watermark that signifies is used before any actual watermark has been generated.

Constructor Summary

Constructors
Constructor Description

Watermark(long timestamp)
Creates a new watermark with the given timestamp in milliseconds.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`equals(Object o)`
`long`	`getTimestamp()`	Returns the timestamp associated with this `Watermark` in milliseconds.
`int`	`hashCode()`
`String`	`toString()`

Methods inherited from class org.apache.flink.streaming.runtime.streamrecord.StreamElement
asLatencyMarker, asRecord, asRecordAttributes, asWatermark, asWatermarkStatus, isLatencyMarker, isRecord, isRecordAttributes, isWatermark, isWatermarkStatus

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - MAX_WATERMARK
```
public static final Watermark MAX_WATERMARK
```
    The watermark that signifies end-of-event-time.
  - UNINITIALIZED
```
public static final Watermark UNINITIALIZED
```
    The watermark that signifies is used before any actual watermark has been generated.
  - timestamp
```
protected final long timestamp
```
    The timestamp of the watermark in milliseconds.
- Constructor Detail
  - Watermark
```
public Watermark(long timestamp)
```
    Creates a new watermark with the given timestamp in milliseconds.
- Method Detail
  - getTimestamp
```
public long getTimestamp()
```
    Returns the timestamp associated with this Watermark in milliseconds.
  - equals
```
public boolean equals(Object o)
```
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object