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
