Hello Sachin, I am with you that ideally the windowing segmentation implementation should be totally abstracted from users but today it is a bit confusing to understand. I have filed JIRA some time ago to improve on this end:
https://issues.apache.org/jira/browse/KAFKA-3596 So to your example, if a "far future record" was received whose timestamp is beyond current time + the retention period, it could potentially cause the current window to be dropped. Guozhang On Fri, Dec 2, 2016 at 10:07 PM, Sachin Mittal <sjmit...@gmail.com> wrote: > Hi, > I think now it makes all the sense. The field I was using for timestamp > extractor contains timestamps which spans for greater than a day's duration > and it worked for wall clock because for short duration timestamps were in > day's range. > > I wanted to understand one thing: > Say I have a timestamp extractor field and as record gets ingested future > records will have increasing values for the timestamp. > > Now lets say default duration is one day. At a future time a record will > have timestamp which now is greater than the initial day's range. > What will happen then, it will create a new segment and then create windows > in it for the next day's duration? > What happens if now it gets a record from the previous day, will it get > discarded or will it again have just the single value aggregated in it > (previous values are lost). > So when new segment is create as I understand does it retain the older > segments data. > > This is bit confusing, so would be helpful if you can explain in bit more > detail. > > Thanks > Sachin > > > On Sat, Dec 3, 2016 at 5:18 AM, Guozhang Wang <wangg...@gmail.com> wrote: > > > Sachin, > > > > One thing to note is that the retention of the windowed stores works by > > keeping multiple segments of the stores where each segments stores a time > > range which can potentially span multiple windows, if a new window needs > to > > be created that is further from the oldest segment's time range + > retention > > period (from your code it seems you do not override it from > > TimeWindows.of("stream-table", > > 10 * 1000L).advanceBy(5 * 1000L), via until(...)), so the default of one > > day is used. > > > > So with WallclockTimeExtractor since it is using system time, it wont > give > > you timestamps that span for more than a day during a short period of > time, > > but if your own defined timestamps expand that value, then old segments > > will be dropped immediately and hence the aggregate values will be > returned > > as a single value. > > > > Guozhang > > > > > > On Fri, Dec 2, 2016 at 11:58 AM, Matthias J. Sax <matth...@confluent.io> > > wrote: > > > > > The extractor is used in > > > > > > org.apache.kafka.streams.processor.internals. > RecordQueue#addRawRecords() > > > > > > Let us know, if you could resolve the problem or need more help. > > > > > > -Matthias > > > > > > On 12/2/16 11:46 AM, Sachin Mittal wrote: > > > > https://github.com/SOHU-Co/kafka-node/ this is the node js client i > am > > > > using. The version is 0.5x. Can you please tell me what code in > streams > > > > calls the timestamp extractor. I can look there to see if there is > any > > > > issue. > > > > > > > > Again issue happens only when producing the messages using producer > > that > > > is > > > > compatible with kafka version 0.8x. I see that this producer does not > > > send > > > > a record timestamp as this was introduced in version 0.10 only. > > > > > > > > Thanks > > > > Sachin > > > > > > > > On 3 Dec 2016 1:03 a.m., "Matthias J. Sax" <matth...@confluent.io> > > > wrote: > > > > > > > >> I am not sure what is happening. That's why it would be good to > have a > > > >> toy example to reproduce the issue. > > > >> > > > >> What do you mean by "Kafka node version 0.5"? > > > >> > > > >> -Matthias > > > >> > > > >> On 12/2/16 11:30 AM, Sachin Mittal wrote: > > > >>> I can provide with the data but data does not seem to be the issue. > > > >>> If I submit the same data and use same timestamp extractor using > the > > > >> java > > > >>> client with kafka version 0.10.0.1 aggregation works fine. > > > >>> I find the issue only when submitting the data with kafka node > > version > > > >> 0.5. > > > >>> It looks like the stream does not extract the time correctly in > that > > > >> case. > > > >>> > > > >>> Thanks > > > >>> Sachin > > > >>> > > > >>> On 2 Dec 2016 11:41 p.m., "Matthias J. Sax" <matth...@confluent.io > > > > > >> wrote: > > > >>> > > > >>>> Can you provide example input data (including timetamps) and > result. > > > >>>> What is the expected result (ie, what aggregation do you apply)? > > > >>>> > > > >>>> > > > >>>> -Matthias > > > >>>> > > > >>>> On 12/2/16 7:43 AM, Sachin Mittal wrote: > > > >>>>> Hi, > > > >>>>> After much debugging I found an issue with timestamp extractor. > > > >>>>> > > > >>>>> If I use a custom timestamp extractor with following code: > > > >>>>> public static class MessageTimestampExtractor implements > > > >>>>> TimestampExtractor { > > > >>>>> public long extract(ConsumerRecord<Object, Object> > record) > > { > > > >>>>> if (record.value() instanceof Message) { > > > >>>>> return ((Message) record.value()).ts; > > > >>>>> } else { > > > >>>>> return record.timestamp(); > > > >>>>> } > > > >>>>> } > > > >>>>> } > > > >>>>> > > > >>>>> Here message has a long field ts which stores the timestamp, the > > > >>>>> aggregation does not work. > > > >>>>> Note I have checked and ts has valid timestamp values. > > > >>>>> > > > >>>>> However if I replace it with say WallclockTimestampExtractor > > > >> aggregation > > > >>>> is > > > >>>>> working fine. > > > >>>>> > > > >>>>> I do not understand what could be the issue here. > > > >>>>> > > > >>>>> Also note I am using kafka streams version 0.10.0.1 and I am > > > publishing > > > >>>>> messages via > > > >>>>> https://github.com/SOHU-Co/kafka-node/ whose version is quite > old > > > >> 0.5.x > > > >>>>> > > > >>>>> Let me know if there is some bug in time stamp extractions. > > > >>>>> > > > >>>>> Thanks > > > >>>>> Sachin > > > >>>>> > > > >>>>> > > > >>>>> > > > >>>>> On Mon, Nov 28, 2016 at 11:52 PM, Guozhang Wang < > > wangg...@gmail.com> > > > >>>> wrote: > > > >>>>> > > > >>>>>> Sachin, > > > >>>>>> > > > >>>>>> This is indeed a bit wired, and we'd like to try to re-produce > > your > > > >>>> issue > > > >>>>>> locally. Do you have a sample input data for us to try out? > > > >>>>>> > > > >>>>>> Guozhang > > > >>>>>> > > > >>>>>> On Fri, Nov 25, 2016 at 10:12 PM, Sachin Mittal < > > sjmit...@gmail.com > > > > > > > >>>>>> wrote: > > > >>>>>> > > > >>>>>>> Hi, > > > >>>>>>> I fixed that sorted set issue but I am facing a weird problem > > > which I > > > >>>> am > > > >>>>>>> not able to replicate. > > > >>>>>>> > > > >>>>>>> Here is the sample problem that I could isolate: > > > >>>>>>> My class is like this: > > > >>>>>>> public static class Message implements Comparable<Message> > { > > > >>>>>>> public long ts; > > > >>>>>>> public String message; > > > >>>>>>> public String key; > > > >>>>>>> public Message() {}; > > > >>>>>>> public Message(long ts, String message, String key) { > > > >>>>>>> this.ts = ts; > > > >>>>>>> this.key = key; > > > >>>>>>> this.message = message; > > > >>>>>>> } > > > >>>>>>> public int compareTo(Message paramT) { > > > >>>>>>> long ts1 = paramT.ts; > > > >>>>>>> return ts > ts1 ? 1 : -1; > > > >>>>>>> } > > > >>>>>>> } > > > >>>>>>> > > > >>>>>>> pipeline is like this: > > > >>>>>>> builder.stream(Serdes.String(), messageSerde, > > > "test-window-stream")\ > > > >>>>>>> .map(new KeyValueMapper<String, Message, KeyValue<String, > > > >> Message>>() > > > >>>> { > > > >>>>>>> public KeyValue<String, Message> apply(String key, Message > > > >> value) > > > >>>> { > > > >>>>>>> return new KeyValue<String, Message>(value.key, > value); > > > >>>>>>> } > > > >>>>>>> }) > > > >>>>>>> .through(Serdes.String(), messageSerde, > "test-window-key-stream") > > > >>>>>>> .aggregateByKey(new Initializer<SortedSet<Message>>() { > > > >>>>>>> public SortedSet<Message> apply() { > > > >>>>>>> return new TreeSet<Message>(); > > > >>>>>>> } > > > >>>>>>> }, new Aggregator<String, Message, SortedSet<Message>>() { > > > >>>>>>> public SortedSet<Message> apply(String aggKey, Message > value, > > > >>>>>>> SortedSet<Message> aggregate) { > > > >>>>>>> aggregate.add(value); > > > >>>>>>> return aggregate; > > > >>>>>>> } > > > >>>>>>> }, TimeWindows.of("stream-table", 10 * 1000L).advanceBy(5 * > > 1000L), > > > >>>>>>> Serdes.String(), messagesSerde) > > > >>>>>>> .foreach(new ForeachAction<Windowed<String>, > > > SortedSet<Message>>() { > > > >>>>>>> public void apply(Windowed<String> key, SortedSet<Message> > > > >>>> messages) > > > >>>>>> { > > > >>>>>>> ... > > > >>>>>>> } > > > >>>>>>> }); > > > >>>>>>> > > > >>>>>>> So basically I rekey the original message into another topic > and > > > then > > > >>>>>>> aggregate it based on that key. > > > >>>>>>> What I have observed is that when I used windowed aggregation > the > > > >>>>>>> aggregator does not use previous aggregated value. > > > >>>>>>> > > > >>>>>>> public SortedSet<Message> apply(String aggKey, Message value, > > > >>>>>>> SortedSet<Message> aggregate) { > > > >>>>>>> aggregate.add(value); > > > >>>>>>> return aggregate; > > > >>>>>>> } > > > >>>>>>> > > > >>>>>>> So in the above function the aggregate is an empty set of every > > > value > > > >>>>>>> entering into pipeline. When I remove the windowed aggregation, > > the > > > >>>>>>> aggregate set retains previously aggregated values in the set. > > > >>>>>>> > > > >>>>>>> I am just not able to wrap my head around it. When I ran this > > type > > > of > > > >>>>>> test > > > >>>>>>> locally on windows it is working fine. However a similar > pipeline > > > >> setup > > > >>>>>>> when run against production on linux is behaving strangely and > > > always > > > >>>>>>> getting an empty aggregate set. > > > >>>>>>> Any idea what could be the reason, where should I look at the > > > >> problem. > > > >>>>>> Does > > > >>>>>>> length of key string matters here? I will later try to run the > > same > > > >>>>>> simple > > > >>>>>>> setup on linux and see what happens. But this is a very strange > > > >>>> behavior. > > > >>>>>>> > > > >>>>>>> Thanks > > > >>>>>>> Sachin > > > >>>>>>> > > > >>>>>>> > > > >>>>>>> > > > >>>>>>> On Wed, Nov 23, 2016 at 12:04 AM, Guozhang Wang < > > > wangg...@gmail.com> > > > >>>>>>> wrote: > > > >>>>>>> > > > >>>>>>>> Hello Sachin, > > > >>>>>>>> > > > >>>>>>>> In the implementation of SortedSet, if the object's > implemented > > > the > > > >>>>>>>> Comparable interface, that compareTo function is applied in " > > > >>>>>>>> aggregate.add(value);", and hence if it returns 0, this > element > > > will > > > >>>>>> not > > > >>>>>>> be > > > >>>>>>>> added since it is a Set. > > > >>>>>>>> > > > >>>>>>>> > > > >>>>>>>> Guozhang > > > >>>>>>>> > > > >>>>>>>> > > > >>>>>>>> On Mon, Nov 21, 2016 at 10:06 PM, Sachin Mittal < > > > sjmit...@gmail.com > > > >>> > > > >>>>>>>> wrote: > > > >>>>>>>> > > > >>>>>>>>> Hi, > > > >>>>>>>>> What I find is that when I use sorted set as aggregation it > > fails > > > >> to > > > >>>>>>>>> aggregate the values which have compareTo returning 0. > > > >>>>>>>>> > > > >>>>>>>>> My class is like this: > > > >>>>>>>>> public class Message implements Comparable<Message> { > > > >>>>>>>>> public long ts; > > > >>>>>>>>> public String message; > > > >>>>>>>>> public Message() {}; > > > >>>>>>>>> public Message(long ts, String message) { > > > >>>>>>>>> this.ts = ts; > > > >>>>>>>>> this.message = message; > > > >>>>>>>>> } > > > >>>>>>>>> public int compareTo(Message paramT) { > > > >>>>>>>>> long ts1 = paramT.ts; > > > >>>>>>>>> return ts == ts1 ? 0 : ts > ts1 ? 1 : -1; > > > >>>>>>>>> } > > > >>>>>>>>> } > > > >>>>>>>>> > > > >>>>>>>>> pipeline is like this: > > > >>>>>>>>> builder.stream(Serdes.String(), messageSerde, > > > >> "test-window-stream") > > > >>>>>>>>> .aggregateByKey(new Initializer<SortedSet<Message>>() { > > > >>>>>>>>> public SortedSet<Message> apply() { > > > >>>>>>>>> return new TreeSet<Message>(); > > > >>>>>>>>> } > > > >>>>>>>>> }, new Aggregator<String, Message, SortedSet<Message>>() { > > > >>>>>>>>> public SortedSet<Message> apply(String aggKey, Message > > value, > > > >>>>>>>>> SortedSet<Message> aggregate) { > > > >>>>>>>>> aggregate.add(value); > > > >>>>>>>>> return aggregate; > > > >>>>>>>>> } > > > >>>>>>>>> }, TimeWindows.of("stream-table", 10 * 1000L).advanceBy(5 * > > > 1000L), > > > >>>>>>>>> Serdes.String(), messagesSerde) > > > >>>>>>>>> .foreach(new ForeachAction<Windowed<String>, > > > >> SortedSet<Message>>() { > > > >>>>>>>>> public void apply(Windowed<String> key, > SortedSet<Message> > > > >>>>>>> messages) > > > >>>>>>>> { > > > >>>>>>>>> ... > > > >>>>>>>>> } > > > >>>>>>>>> }); > > > >>>>>>>>> > > > >>>>>>>>> So any message published between 10 and 20 seconds gets > > > aggregated > > > >> in > > > >>>>>>> 10 > > > >>>>>>>> - > > > >>>>>>>>> 20 bucket and I print the size of the set. > > > >>>>>>>>> However output I get is following: > > > >>>>>>>>> > > > >>>>>>>>> Published: 14 > > > >>>>>>>>> Aggregated: 10 20 -> 1 > > > >>>>>>>>> > > > >>>>>>>>> Published: 18 > > > >>>>>>>>> Aggregated: 10 20 -> 2 > > > >>>>>>>>> > > > >>>>>>>>> Published: 11 > > > >>>>>>>>> Aggregated: 10 20 -> 3 > > > >>>>>>>>> > > > >>>>>>>>> Published: 17 > > > >>>>>>>>> Aggregated: 10 20 -> 4 > > > >>>>>>>>> > > > >>>>>>>>> Published: 14 > > > >>>>>>>>> Aggregated: 10 20 -> 4 > > > >>>>>>>>> > > > >>>>>>>>> Published: 15 > > > >>>>>>>>> Aggregated: 10 20 -> 5 > > > >>>>>>>>> > > > >>>>>>>>> Published: 12 > > > >>>>>>>>> Aggregated: key2 10 20 -> 6 > > > >>>>>>>>> > > > >>>>>>>>> Published: 12 > > > >>>>>>>>> Aggregated: 10 20 -> 6 > > > >>>>>>>>> > > > >>>>>>>>> So if you see any message that occurs again for same second, > > > where > > > >>>>>>>>> compareTo returns 0, it fails to get aggregated in the > > pipeline. > > > >>>>>>>>> Notice ones published at 14 and 12 seconds. > > > >>>>>>>>> > > > >>>>>>>>> Now I am not sure if problem is with Java ie I should use > > > >> Comparator > > > >>>>>>>>> interface and not Comparable for my Message object. Or the > > > problem > > > >> is > > > >>>>>>>> with > > > >>>>>>>>> Kafka stream or with serializing and de-serializing the set > of > > > >>>>>>> messages. > > > >>>>>>>> If > > > >>>>>>>>> I replace Set with List all is working fine. > > > >>>>>>>>> > > > >>>>>>>>> Anyway any ideas here would be appreciated, meanwhile let me > > see > > > >> what > > > >>>>>>> is > > > >>>>>>>>> the best java practice here. > > > >>>>>>>>> > > > >>>>>>>>> Thanks > > > >>>>>>>>> Sachin > > > >>>>>>>>> > > > >>>>>>>>> > > > >>>>>>>>> > > > >>>>>>>>> On Mon, Nov 21, 2016 at 8:29 PM, Michael Noll < > > > >> mich...@confluent.io> > > > >>>>>>>>> wrote: > > > >>>>>>>>> > > > >>>>>>>>>> On Mon, Nov 21, 2016 at 1:06 PM, Sachin Mittal < > > > >> sjmit...@gmail.com > > > >>>>>>> > > > >>>>>>>>> wrote: > > > >>>>>>>>>> > > > >>>>>>>>>>> I am using kafka_2.10-0.10.0.1. > > > >>>>>>>>>>> Say I am having a window of 60 minutes advanced by 15 > > minutes. > > > >>>>>>>>>>> If the stream app using timestamp extractor puts the > message > > in > > > >>>>>> one > > > >>>>>>>> or > > > >>>>>>>>>> more > > > >>>>>>>>>>> bucket(s), it will get aggregated in those buckets. > > > >>>>>>>>>>> I assume this statement is correct. > > > >>>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>> Yes. > > > >>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>>> > > > >>>>>>>>>>> Also say when I restart the streams application then bucket > > > >>>>>>>> aggregation > > > >>>>>>>>>>> will resume from last point of halt. > > > >>>>>>>>>>> I hope this is also correct. > > > >>>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>> Yes. > > > >>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>>> What I noticed that once a message is placed in one bucket, > > > that > > > >>>>>>>> bucket > > > >>>>>>>>>> was > > > >>>>>>>>>>> not getting new messages. > > > >>>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>> This should not happen... > > > >>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>>> However when I ran a small test case replicating that, it > is > > > >>>>>>> working > > > >>>>>>>>>>> properly. There maybe some issues in application reset. > > > >>>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>> ...and apparently it works (as expected) in your small test > > > case. > > > >>>>>>>>>> > > > >>>>>>>>>> Do you have any further information that you could share > with > > us > > > >> so > > > >>>>>>> we > > > >>>>>>>>> can > > > >>>>>>>>>> help you better? What's the difference, for example, > between > > > your > > > >>>>>>>>> "normal" > > > >>>>>>>>>> use case and the small test case you have been referring to? > > > >>>>>>>>>> > > > >>>>>>>>>> > > > >>>>>>>>>> -Michael > > > >>>>>>>>>> > > > >>>>>>>>> > > > >>>>>>>> > > > >>>>>>>> > > > >>>>>>>> > > > >>>>>>>> -- > > > >>>>>>>> -- Guozhang > > > >>>>>>>> > > > >>>>>>> > > > >>>>>> > > > >>>>>> > > > >>>>>> > > > >>>>>> -- > > > >>>>>> -- Guozhang > > > >>>>>> > > > >>>>> > > > >>>> > > > >>>> > > > >>> > > > >> > > > >> > > > > > > > > > > > > > > > > -- > > -- Guozhang > > > -- -- Guozhang
