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From Kostas Kloudas <k.klou...@data-artisans.com>
Subject Re: Regarding ordering of events
Date Thu, 05 Jan 2017 11:16:15 GMT
Hi Abdul,

Flink provides no ordering guarantees on the elements within a window.
The only “order” it guarantees is that the results referring to window-1 are
going to be emitted before those of window-2 (assuming that window-1 precedes window-2).

Thanks,
Kostas

> On Jan 5, 2017, at 11:57 AM, Abdul Salam Shaikh <abd.salam.shaikh@gmail.com> wrote:
> 
> Hi, 
> 
> I am using a JSON file as the source for the streaming (in the ascending order of the
field Umlaufsekunde)which has events as follows: 
> 
> {"event":[{"Umlaufsekunde":115}]}
> {"event":[{"Umlaufsekunde":135}]}
> {"event":[{"Umlaufsekunde":135}]}
> {"event":[{"Umlaufsekunde":145}]}
> {"event":[{"Umlaufsekunde":155}]}
> {"event":[{"Umlaufsekunde":155}]}
> {"event":[{"Umlaufsekunde":185}]}
> {"event":[{"Umlaufsekunde":195}]}
> {"event":[{"Umlaufsekunde":195}]}
> {"event":[{"Umlaufsekunde":205}]}
> {"event":[{"Umlaufsekunde":245}]}
> 
> However, when I try to print the stream, it is unordered as given below: 
> 1> (115,null,1483517983252,1190)  -- The first value indicating Umlaufsekunde
> 2> (135,null,1483517984877,1190)
> 2> (155,null,1483517986861,1190)
> 4> (145,null,1483517985752,1190)
> 3> (135,null,1483517985424,1190)
> 4> (195,null,1483517990736,1190)
> 4> (255,null,1483517997424,1190)
> 2> (205,null,1483517991518,1190)
> 2> (275,null,1483517999330,1190)
> 2> (385,null,1483518865371,1190)
> 2> (395,null,1483518866840,1190)
> 1> (155,null,1483517986533,1190)
> 4> (285,null,1483518000189,1190)
> 4> (395,null,1483518866231,1190)
> 
> I have also tried using the Timestamps and Watermarks but no luck as follows: 
> 
> public class TimestampExtractor implements AssignerWithPeriodicWatermarks<Tuple5<String,
Long, List<Lane>, Long, Long>>{
>     
>     private long currentMaxTimestamp;
> 
>     @Override
>     public Watermark getCurrentWatermark() {
>         return new Watermark(currentMaxTimestamp);   
>     }
> 
>     @Override
>     public long extractTimestamp(Tuple5<String, Long> element, long previousElementTimestamp)
{
>         long timestamp = element.getField(1);
>         currentMaxTimestamp = timestamp;
>         return currentMaxTimestamp;
>   }
>     
> }
> 
> Could anyone suggest how do I handle this problem for the arrival of events in order
? 
> 
> ​Thanks!​
> 
> 


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