Hi, the reason why the last element might never be emitted is the way the ascending timestamp extractor works. I'll try and explain with an example.
Let's say we have a window size of 2 milliseconds, elements arrive starting with timestamp 0, window begin timestamp is inclusive, end timestamp is exclusive: Element 0, Timestamp 0 (at this point the watermark is -1) Element 1, Timestamp 1 (at this point the watermark is 0) Element 2, Timestamp 1 (at this point the watermark is still 0) Element 3, Timestamp 2 (at this point the watermark is 1) now we can process the window (0, 2) because we know from the watermark that no elements can arrive for that window anymore. The window contains elements 0,1,2 Element 4, Timestamp 3 (at this point the watermark is 2) Element 5, Timestamp 4 (at this point the watermark is 3) now we can process window (2, 4). The window contains elements 3,4. At this point, we have Element 5 sitting in internal buffers for window (4, 6) but if we don't receive further elements the watermark will never advance and we will never process that window. If, however, we get new elements at some point the watermark advances and we don't have a problem. That's what I meant when I said that you shouldn't have a problem if data keeps continuously arriving. Cheers, Aljoscha On Tue, 28 Jun 2016 at 17:14 Vinay Patil <vinay18.pa...@gmail.com> wrote: > Hi Aljoscha, > > Thanks a lot for your inputs. > > I still did not get you when you say you will not face this issue in case > of continuous stream, lets consider the following example : > Assume that the stream runs continuously from Monday to Friday, and on > Friday it stops after 5.00 PM , will I still face this issue ? > > I am actually not able to understand how it will differ in real time > streams. > > Regards, > Vinay Patil > > On Tue, Jun 28, 2016 at 5:07 PM, Aljoscha Krettek <aljos...@apache.org> > wrote: > > > Hi, > > ingestion time can only be used if you don't care about the timestamp in > > the elements. So if you have those you should probably use event time. > > > > If your timestamps really are strictly increasing then the ascending > > extractor is good. And if you have a continuous stream of incoming > elements > > you will not see the behavior of not getting the last elements. > > > > By the way, when using Kafka you can also embed the timestamp extractor > > directly in the Kafka consumer. This is described here: > > > > > https://ci.apache.org/projects/flink/flink-docs-master/apis/streaming/connectors/kafka.html#kafka-consumers-and-timestamp-extractionwatermark-emission > > > > Cheers, > > Aljoscha > > > > On Tue, 28 Jun 2016 at 11:44 Vinay Patil <vinay18.pa...@gmail.com> > wrote: > > > > > Hi Aljoscha, > > > > > > Thank you for your response. > > > So do you suggest to use different approach for extracting timestamp > (as > > > given in document) instead of AscendingTimeStamp Extractor ? > > > Is that the reason I am seeing this unexpected behaviour ? in case of > > > continuous stream I would not see any data loss ? > > > > > > Also assuming that the records are always going to be in order , which > is > > > the best approach : Ingestion Time or Event Time ? > > > > > > > > > > > > Regards, > > > Vinay Patil > > > > > > On Tue, Jun 28, 2016 at 2:41 PM, Aljoscha Krettek <aljos...@apache.org > > > > > wrote: > > > > > > > Hi, > > > > first regarding tumbling windows: even if you have 5 minute windows > it > > > can > > > > happen that elements that are only seconds apart go into different > > > windows. > > > > Consider the following case: > > > > > > > > | x | x | > > > > > > > > These are two 5-mintue windows and the two elements are only seconds > > > apart > > > > but go into different windows because windows are aligned to epoch. > > > > > > > > Now, for the ascending timestamp extractor. The reason this can > behave > > in > > > > unexpected ways is that it emits a watermark that is "last timestamp > - > > > 1", > > > > i.e. if it has seen timestamp t it can only emit watermark t-1 > because > > > > there might be other elements with timestamp t arriving. If you have > a > > > > continuous stream of elements you wouldn't notice this. Only in this > > > > constructed example does it become visible. > > > > > > > > Cheers, > > > > Aljoscha > > > > > > > > On Tue, 28 Jun 2016 at 06:04 Vinay Patil <vinay18.pa...@gmail.com> > > > wrote: > > > > > > > > > Hi, > > > > > > > > > > Following is the timestamp I am getting from DTO, here is the > > timestamp > > > > > difference between the two records : > > > > > 1466115892162154279 > > > > > 1466116026233613409 > > > > > > > > > > So the time difference is roughly 3 min, even if I apply the window > > of > > > > 5min > > > > > , I am not getting the last record (last timestamp value above), > > > > > using ascending timestamp extractor for generating the timestamp > > > > (assuming > > > > > that the timestamp are always in order) > > > > > > > > > > I was at-least expecting data to reach the co-group function. > > > > > What could be the reason for the data loss ? The data we are > getting > > is > > > > > critical, hence we cannot afford to loose any data > > > > > > > > > > > > > > > Regards, > > > > > Vinay Patil > > > > > > > > > > On Mon, Jun 27, 2016 at 11:31 PM, Vinay Patil < > > vinay18.pa...@gmail.com > > > > > > > > > wrote: > > > > > > > > > > > Just an update, when I keep IngestionTime and remove the > timestamp > > I > > > am > > > > > > generating, I am getting all the records, but for Event Time I am > > > > getting > > > > > > one less record, I checked the Time Difference between two > records, > > > it > > > > > is 3 > > > > > > min, I tried keeping the window time to 5 mins, but that even did > > not > > > > > work. > > > > > > > > > > > > Even when I try assigning timestamp for IngestionTime, I get one > > > record > > > > > > less, so should I safely use Ingestion Time or is it always > > advisable > > > > to > > > > > > use EventTime ? > > > > > > > > > > > > Regards, > > > > > > Vinay Patil > > > > > > > > > > > > On Mon, Jun 27, 2016 at 8:16 PM, Vinay Patil < > > > vinay18.pa...@gmail.com> > > > > > > wrote: > > > > > > > > > > > >> Hi , > > > > > >> > > > > > >> Actually I am only publishing 5 messages each to two different > > kafka > > > > > >> topics (using Junit), even if I keep the window to 500 seconds > the > > > > > result > > > > > >> is same. > > > > > >> > > > > > >> I am not understanding why it is not sending the 5th element to > > > > co-group > > > > > >> operator even when the keys are same. > > > > > >> > > > > > >> I actually cannot share the actual client code. > > > > > >> But this is what the streams look like : > > > > > >> sourceStream.coGroup(destStream) > > > > > >> here the sourceStream and destStream is actually > > Tuple2<String,DTO> > > > , > > > > > and > > > > > >> the ElementSelector returns tuple.f0 which is the key. > > > > > >> > > > > > >> I am generating the timestamp based on a field from the DTO > which > > is > > > > > >> guaranteed to be in order. > > > > > >> > > > > > >> Will using the triggers help here ? > > > > > >> > > > > > >> > > > > > >> Regards, > > > > > >> Vinay Patil > > > > > >> > > > > > >> *+91-800-728-4749* > > > > > >> > > > > > >> On Mon, Jun 27, 2016 at 7:05 PM, Aljoscha Krettek < > > > > aljos...@apache.org> > > > > > >> wrote: > > > > > >> > > > > > >>> Hi, > > > > > >>> what timestamps are you assigning? Is it guaranteed that all of > > > them > > > > > >>> would > > > > > >>> fall into the same 30 second window? > > > > > >>> > > > > > >>> The issue with duplicate printing in the ElementSelector is > > > strange? > > > > > >>> Could > > > > > >>> you post a more complete code example so that I can reproduce > the > > > > > >>> problem? > > > > > >>> > > > > > >>> Cheers, > > > > > >>> Aljoscha > > > > > >>> > > > > > >>> On Mon, 27 Jun 2016 at 13:21 Vinay Patil < > > vinay18.pa...@gmail.com> > > > > > >>> wrote: > > > > > >>> > > > > > >>> > Hi , > > > > > >>> > > > > > > >>> > I am able to get the matching and non-matching elements. > > > > > >>> > > > > > > >>> > However when I am unit testing the code , I am getting one > > record > > > > > less > > > > > >>> > inside the overriden cogroup function. > > > > > >>> > Testing the following way : > > > > > >>> > > > > > > >>> > 1) Insert 5 messages into local kafka topic (test1) > > > > > >>> > 2) Insert different 5 messages into local kafka topic (test2) > > > > > >>> > 3) Consume 1) and 2) and I have two different kafka streams > > > > > >>> > 4) Generate ascending timestamp(using Event Time) for both > > > streams > > > > > and > > > > > >>> > create key(String) > > > > > >>> > > > > > > >>> > Now till 4) I am able to get all the records (checked by > > printing > > > > the > > > > > >>> > stream in text file) > > > > > >>> > > > > > > >>> > However when I send the stream to co-group operator, I am > > > receiving > > > > > one > > > > > >>> > less record, using the following syntax: > > > > > >>> > > > > > > >>> > sourceStream.coGroup(destStream) > > > > > >>> > .where(new ElementSelector()) > > > > > >>> > .equalTo(new ElementSelector()) > > > > > >>> > .window(TumblingEventTimeWindows.of(Time.seconds(30))) > > > > > >>> > .apply(new JoinStreams); > > > > > >>> > > > > > > >>> > Also in the Element Selector I have inserted a sysout, I am > > > getting > > > > > 20 > > > > > >>> > sysouts instead of 10 (10 sysouts for source and 10 for dest > > > > stream) > > > > > >>> > > > > > > >>> > Unable to understand why one record is coming less to > co-group > > > > > >>> > > > > > > >>> > > > > > > >>> > > > > > > >>> > Regards, > > > > > >>> > Vinay Patil > > > > > >>> > > > > > > >>> > On Wed, Jun 15, 2016 at 1:39 PM, Fabian Hueske < > > > fhue...@gmail.com> > > > > > >>> wrote: > > > > > >>> > > > > > > >>> > > Can you add a flag to each element emitted by the > > > CoGroupFunction > > > > > >>> that > > > > > >>> > > indicates whether it was joined or not? > > > > > >>> > > Then you can use split to distinguish between both cases > and > > > > handle > > > > > >>> both > > > > > >>> > > streams differently. > > > > > >>> > > > > > > > >>> > > Best, Fabian > > > > > >>> > > > > > > > >>> > > 2016-06-15 6:45 GMT+02:00 Vinay Patil < > > vinay18.pa...@gmail.com > > > >: > > > > > >>> > > > > > > > >>> > > > Hi Jark, > > > > > >>> > > > > > > > > >>> > > > I am able to get the non-matching elements in a stream :, > > > > > >>> > > > > > > > > >>> > > > Of-course we can collect the matching elements in the > same > > > > stream > > > > > >>> as > > > > > >>> > > well, > > > > > >>> > > > however I want to perform additional operations on the > > joined > > > > > >>> stream > > > > > >>> > > before > > > > > >>> > > > writing it to S3, so I would have to include a separate > > join > > > > > >>> operator > > > > > >>> > for > > > > > >>> > > > the same two streams, right ? > > > > > >>> > > > Correct me if I am wrong. > > > > > >>> > > > > > > > > >>> > > > I have pasted the dummy code which collects the > > non-matching > > > > > >>> records (i > > > > > >>> > > > have to perform this on the actual data, correct me if I > am > > > > dong > > > > > >>> > wrong). > > > > > >>> > > > > > > > > >>> > > > sourceStream.coGroup(destStream).where(new > > > > > >>> > ElementSelector()).equalTo(new > > > > > >>> > > > ElementSelector()) > > > > > >>> > > > .window(TumblingEventTimeWindows.of(Time.seconds(30))) > > > > > >>> > > > .apply(new CoGroupFunction<Integer, Integer, Integer>() { > > > > > >>> > > > > > > > > >>> > > > private static final long serialVersionUID = > > > > > 6408179761497497475L; > > > > > >>> > > > > > > > > >>> > > > @Override > > > > > >>> > > > public void coGroup(Iterable<Integer> paramIterable, > > > > > >>> Iterable<Integer> > > > > > >>> > > > paramIterable1, > > > > > >>> > > > Collector<Integer> paramCollector) throws Exception { > > > > > >>> > > > long exactSizeIfKnown = > > > > > >>> > > paramIterable.spliterator().getExactSizeIfKnown(); > > > > > >>> > > > long exactSizeIfKnown2 = > > > > > >>> > > > paramIterable1.spliterator().getExactSizeIfKnown(); > > > > > >>> > > > if(exactSizeIfKnown == 0 ) { > > > > > >>> > > > paramCollector.collect(paramIterable1.iterator().next()); > > > > > >>> > > > } else if (exactSizeIfKnown2 == 0) { > > > > > >>> > > > paramCollector.collect(paramIterable.iterator().next()); > > > > > >>> > > > } > > > > > >>> > > > } > > > > > >>> > > > }).print(); > > > > > >>> > > > > > > > > >>> > > > Regards, > > > > > >>> > > > Vinay Patil > > > > > >>> > > > > > > > > >>> > > > > > > > > >>> > > > On Tue, Jun 14, 2016 at 1:37 PM, Vinay Patil < > > > > > >>> vinay18.pa...@gmail.com> > > > > > >>> > > > wrote: > > > > > >>> > > > > > > > > >>> > > > > You are right, debugged it for all elements , I can do > > that > > > > > now. > > > > > >>> > > > > Thanks a lot. > > > > > >>> > > > > > > > > > >>> > > > > Regards, > > > > > >>> > > > > Vinay Patil > > > > > >>> > > > > > > > > > >>> > > > > On Tue, Jun 14, 2016 at 11:56 AM, Jark Wu < > > > > > >>> > wuchong...@alibaba-inc.com> > > > > > >>> > > > > wrote: > > > > > >>> > > > > > > > > > >>> > > > >> In `coGroup(Iterable<Integer> iter1, Iterable<Integer> > > > > iter2, > > > > > >>> > > > >> Collector<Integer> out)` , when both iter1 and iter2 > > are > > > > not > > > > > >>> > empty, > > > > > >>> > > it > > > > > >>> > > > >> means they are matched elements from both stream. > > > > > >>> > > > >> When one of iter1 and iter2 is empty , it means that > > they > > > > are > > > > > >>> > > unmatched. > > > > > >>> > > > >> > > > > > >>> > > > >> > > > > > >>> > > > >> - Jark Wu (wuchong) > > > > > >>> > > > >> > > > > > >>> > > > >> > 在 2016年6月14日，下午12:46，Vinay Patil < > > > vinay18.pa...@gmail.com > > > > > > > > > > >>> 写道： > > > > > >>> > > > >> > > > > > > >>> > > > >> > Hi Matthias , > > > > > >>> > > > >> > > > > > > >>> > > > >> > I did not get you, even if we use Co-Group we have > to > > > > apply > > > > > >>> it on > > > > > >>> > a > > > > > >>> > > > key > > > > > >>> > > > >> > > > > > > >>> > > > >> > sourceStream.coGroup(destStream) > > > > > >>> > > > >> > .where(new ElementSelector()) > > > > > >>> > > > >> > .equalTo(new ElementSelector()) > > > > > >>> > > > >> > > .window(TumblingEventTimeWindows.of(Time.seconds(30))) > > > > > >>> > > > >> > .apply(new CoGroupFunction<Integer, Integer, > > Integer>() > > > { > > > > > >>> > > > >> > private static final long serialVersionUID = > > > > > >>> 6408179761497497475L; > > > > > >>> > > > >> > > > > > > >>> > > > >> > @Override > > > > > >>> > > > >> > public void coGroup(Iterable<Integer> paramIterable, > > > > > >>> > > Iterable<Integer> > > > > > >>> > > > >> > paramIterable1, > > > > > >>> > > > >> > Collector<Integer> paramCollector) throws Exception > { > > > > > >>> > > > >> > Iterator<Integer> iterator = > paramIterable.iterator(); > > > > > >>> > > > >> > while(iterator.hasNext()) { > > > > > >>> > > > >> > } > > > > > >>> > > > >> > } > > > > > >>> > > > >> > }); > > > > > >>> > > > >> > > > > > > >>> > > > >> > when I debug this ,only the matched element from > both > > > > stream > > > > > >>> will > > > > > >>> > > come > > > > > >>> > > > >> in > > > > > >>> > > > >> > the coGroup function. > > > > > >>> > > > >> > > > > > > >>> > > > >> > What I want is how do I check for unmatched elements > > > from > > > > > both > > > > > >>> > > streams > > > > > >>> > > > >> and > > > > > >>> > > > >> > write it to sink. > > > > > >>> > > > >> > > > > > > >>> > > > >> > Regards, > > > > > >>> > > > >> > Vinay Patil > > > > > >>> > > > >> > > > > > > >>> > > > >> > *+91-800-728-4749* > > > > > >>> > > > >> > > > > > > >>> > > > >> > On Tue, Jun 14, 2016 at 2:07 AM, Matthias J. Sax < > > > > > >>> > mj...@apache.org> > > > > > >>> > > > >> wrote: > > > > > >>> > > > >> > > > > > > >>> > > > >> >> You need to do an outer-join. However, there is no > > > > build-in > > > > > >>> > support > > > > > >>> > > > for > > > > > >>> > > > >> >> outer-joins yet. > > > > > >>> > > > >> >> > > > > > >>> > > > >> >> You can use Window-CoGroup to implement the > > outer-join > > > as > > > > > an > > > > > >>> own > > > > > >>> > > > >> operator. > > > > > >>> > > > >> >> > > > > > >>> > > > >> >> > > > > > >>> > > > >> >> -Matthias > > > > > >>> > > > >> >> > > > > > >>> > > > >> >> On 06/13/2016 06:53 PM, Vinay Patil wrote: > > > > > >>> > > > >> >>> Hi, > > > > > >>> > > > >> >>> > > > > > >>> > > > >> >>> I have a question regarding the join operation, > > > consider > > > > > the > > > > > >>> > > > following > > > > > >>> > > > >> >>> dummy example: > > > > > >>> > > > >> >>> > > > > > >>> > > > >> >>> StreamExecutionEnvironment env = > > > > > >>> > > > >> >>> > > StreamExecutionEnvironment.getExecutionEnvironment(); > > > > > >>> > > > >> >>> > > > > > >>> > > > > env.setStreamTimeCharacteristic(TimeCharacteristic.IngestionTime); > > > > > >>> > > > >> >>> DataStreamSource<Integer> sourceStream = > > > > > >>> > > > >> >>> env.fromElements(10,20,23,25,30,33,102,18); > > > > > >>> > > > >> >>> DataStreamSource<Integer> destStream = > > > > > >>> > > > >> >> env.fromElements(20,30,40,50,60,10); > > > > > >>> > > > >> >>> > > > > > >>> > > > >> >>> sourceStream.join(destStream) > > > > > >>> > > > >> >>> .where(new ElementSelector()) > > > > > >>> > > > >> >>> .equalTo(new ElementSelector()) > > > > > >>> > > > >> >>> > > > > > .window(TumblingEventTimeWindows.of(Time.milliseconds(10))) > > > > > >>> > > > >> >>> .apply(new JoinFunction<Integer, Integer, > > Integer>() { > > > > > >>> > > > >> >>> > > > > > >>> > > > >> >>> private static final long serialVersionUID = 1L; > > > > > >>> > > > >> >>> > > > > > >>> > > > >> >>> @Override > > > > > >>> > > > >> >>> public Integer join(Integer paramIN1, Integer > > > paramIN2) > > > > > >>> throws > > > > > >>> > > > >> Exception > > > > > >>> > > > >> >> { > > > > > >>> > > > >> >>> return paramIN1; > > > > > >>> > > > >> >>> } > > > > > >>> > > > >> >>> }).print(); > > > > > >>> > > > >> >>> > > > > > >>> > > > >> >>> I perfectly get the elements that are matching in > > both > > > > the > > > > > >>> > > streams, > > > > > >>> > > > >> >> however > > > > > >>> > > > >> >>> my requirement is to write these matched elements > > and > > > > also > > > > > >>> the > > > > > >>> > > > >> unmatched > > > > > >>> > > > >> >>> elements to sink(S3) > > > > > >>> > > > >> >>> > > > > > >>> > > > >> >>> How do I get the unmatched elements from each > > stream ? > > > > > >>> > > > >> >>> > > > > > >>> > > > >> >>> Regards, > > > > > >>> > > > >> >>> Vinay Patil > > > > > >>> > > > >> >>> > > > > > >>> > > > >> >> > > > > > >>> > > > >> >> > > > > > >>> > > > >> > > > > > >>> > > > >> > > > > > >>> > > > > > > > > > >>> > > > > > > > > >>> > > > > > > > >>> > > > > > > >>> > > > > > >> > > > > > >> > > > > > > > > > > > > > > > > > > > > >
