T - The type of the elements to which this assigner assigns timestamps.
@Deprecated public interface AssignerWithPeriodicWatermarks<T> extends TimestampAssigner<T>
AssignerWithPeriodicWatermarks assigns event time timestamps to elements, and
generates low watermarks that signal event time progress within the stream. These timestamps and
watermarks are used by functions and operators that operate on event time, for example event time
Use this class to generate watermarks in a periodical interval. At most every
milliseconds (configured via
ExecutionConfig.getAutoWatermarkInterval()), the system will
getCurrentWatermark() method to probe for the next watermark value. The system
will generate a new watermark, if the probed value is non-null and has a timestamp larger than
that of the previous watermark (to preserve the contract of ascending watermarks).
The system may call the
getCurrentWatermark() method less often than every
milliseconds, if no new elements arrived since the last call to the method.
Timestamps and watermarks are defined as
longs that represent the milliseconds since
the Epoch (midnight, January 1, 1970 UTC). A watermark with a certain value
that no elements with event timestamps
x is lower or equal to
will occur any more.
|Modifier and Type
|Method and Description
Returns the current watermark.
null to indicate that no new Watermark
The returned watermark will be emitted only if it is non-null and its timestamp is larger than that of the previously emitted watermark (to preserve the contract of ascending watermarks). If the current watermark is still identical to the previous one, no progress in event time has happened since the previous call to this method. If a null value is returned, or the timestamp of the returned watermark is smaller than that of the last emitted one, then no new watermark will be generated.
The interval in which this method is called and Watermarks are generated depends on
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