SingleOutputStreamOperator vs DataStream?

[chrisr123]

I'm trying to get a list of late elements in my Tumbling Windows application
and I noticed
that I need to use SingleOutputStreamOperator<T> instead of DataStream<T> to
get
access to the .sideOutputLateData(...) method.

Can someone explain what the difference is between
SingleOutputStreamOperator and DataStream
and why I need to use this for getting the late data?
Thanks!

Snippet:
 OutputTag<EventBean> lateEventsTag = new
OutputTag<EventBean>("late-events") {};
  SingleOutputStreamOperator<EventBean> windowedEvents = eventStream
                                .keyBy("key")
                                .window(TumblingEventTimeWindows.of(Time.seconds(3)))
                                .sideOutputLateData(lateEventsTag)
                                .process(new EventBeanProcessWindowFunction());
DataStream<EventBean> lateEvents =
windowedEvents.getSideOutput(lateEventsTag);



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[Till Rohrmann]

Hi Chris,

a `DataStream` represents a stream of events which have the same type. A `SingleOutputStreamOperator` is a subclass of `DataStream` and represents a user defined transformation applied to an input `DataStream` and producing an output `DataStream` (represented by itself). Since you can only add a side output to an operator/user defined transformation, you can only access the side output data from a `SingleOutputStreamOperator` and not from a `DataStream`. In this regard, the `SingleOutputStreamOperator` is just a richer version of the `DataStream` which requires a certain context.

Cheers,

Till

On Tue, Jul 24, 2018 at 1:26 PM chrisr123 <[hidden email]> wrote:

I'm trying to get a list of late elements in my Tumbling Windows application
and I noticed
that I need to use SingleOutputStreamOperator<T> instead of DataStream<T> to
get
access to the .sideOutputLateData(...) method.

Can someone explain what the difference is between
SingleOutputStreamOperator and DataStream
and why I need to use this for getting the late data?
Thanks!

Snippet:
 OutputTag<EventBean> lateEventsTag = new
OutputTag<EventBean>("late-events") {};
  SingleOutputStreamOperator<EventBean> windowedEvents = eventStream
                                .keyBy("key")
                                .window(TumblingEventTimeWindows.of(Time.seconds(3)))
                                .sideOutputLateData(lateEventsTag)
                                .process(new EventBeanProcessWindowFunction());
DataStream<EventBean> lateEvents =
windowedEvents.getSideOutput(lateEventsTag);



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