Hi again!
Flink doesn’t order/sort the records according to event time. The preveiling
idea is:
- records will be arriving out of order, operators should handle that
- watermarks are used for indicators of the current lower bound of the event
time “clock”
For examples windowed joins/aggregations assign records to one or more time
windows, collect all of the data belonging to a window and when watermark
exceeds/overtakes the window that when that window is being evaluated.
Piotrek
> On 7 Dec 2018, at 09:22, min....@ubs.com wrote:
>
> Hi,
>
> I am new to Flink.
>
> I have the following small code to use the event time. I did not get the
> result expected, i.e. it print out events in the order of event time.
>
> Did I miss something here?
>
> Regards,
>
> Min
>
>
> --------------Event time------------------
> public static void main(String[] args) throws Exception {
>
> final StreamExecutionEnvironment env =
> StreamExecutionEnvironment.getExecutionEnvironment();
> long start =System.currentTimeMillis();
> DataStream<Event> stream = env.fromElements(new Event(0,start,start),
> new Event(1,start+10,start+10), new
> Event(2,start+20,start-20),
> new Event(3,start+30,start-30), new
> Event(4,start+40,start-40));
>
> stream.map(event -> "RAW order " + event.toString()).print();
>
> stream.assignTimestampsAndWatermarks(new
> AscendingTimestampExtractor<Event>() {
> @Override public long extractAscendingTimestamp(Event element) {
> return element.time1; } })
> .map(event -> "time1 order:: " + event.toString()).print();
>
> stream.assignTimestampsAndWatermarks(new
> AscendingTimestampExtractor<Event>() {
> @Override public long extractAscendingTimestamp(Event element) {
> return element.time2; } })
> .map(event -> "time2 order:: " + event.toString()).print();
>
> env.execute("event time ........");
> }
>
>
> static public class Event {
> int id;
> long time1;
> long time2;
>
> Event(int id, long time1, long time2){
> this <http://this.id/>. <http://this.id/>id <http://this.id/> =id;
> this.time1=time1;
> this.time2=time2;
> }
>
> public String toString() {
> return "id=" + id + "; time1=" + time1 + "; time2=" + time2;
> }
> }
> }
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