org.apache.flink.api.common.eventtime

Class Watermark

java.lang.Object

org.apache.flink.api.common.eventtime.Watermark

All Implemented Interfaces:

Serializable

@Public
public final class Watermark
extends Object
implements Serializable

Watermarks are the progress indicators in the data streams. A watermark signifies that no events with a timestamp smaller or equal to the watermark's time will occur after the water. A watermark with timestamp T indicates that the stream's event time has progressed to time T.

Watermarks are created at the sources and propagate through the streams and operators.

In some cases a watermark is only a heuristic, meaning some events with a lower timestamp may still follow. In that case, it is up to the logic of the operators to decide what to do with the "late events". Operators can for example ignore these late events, route them to a different stream, or send update to their previously emitted results.

When a source reaches the end of the input, it emits a final watermark with timestamp Long.MAX_VALUE, indicating the "end of time".

Note: A stream's time starts with a watermark of Long.MIN_VALUE. That means that all records in the stream with a timestamp of Long.MIN_VALUE are immediately late.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static Watermark	MAX_WATERMARK The watermark that signifies end-of-event-time.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object o)
String	getFormattedTimestamp() Formats the timestamp of this watermark, assuming it is a millisecond timestamp.
long	getTimestamp() Returns the timestamp associated with this Watermark.
int	hashCode()
String	toString()

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.

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.

getFormattedTimestamp

public String getFormattedTimestamp()

Formats the timestamp of this watermark, assuming it is a millisecond timestamp. The returned format is "yyyy-MM-dd HH:mm:ss.SSS".

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