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Posted to dev@kafka.apache.org by "Guozhang Wang (JIRA)" <ji...@apache.org> on 2016/05/19 18:38:12 UTC
[jira] [Updated] (KAFKA-3561) Auto create through topic for KStream
aggregation and join
[ https://issues.apache.org/jira/browse/KAFKA-3561?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Guozhang Wang updated KAFKA-3561:
---------------------------------
Assignee: (was: Guozhang Wang)
> Auto create through topic for KStream aggregation and join
> ----------------------------------------------------------
>
> Key: KAFKA-3561
> URL: https://issues.apache.org/jira/browse/KAFKA-3561
> Project: Kafka
> Issue Type: Bug
> Components: streams
> Reporter: Guozhang Wang
> Labels: api
> Fix For: 0.10.1.0
>
>
> For KStream.join / aggregateByKey operations that requires the streams to be partitioned on the record key, today users should repartition themselves through the "through" call:
> {code}
> stream1 = builder.stream("topic1");
> stream2 = builder.stream("topic2");
> stream3 = stream1.map(/* set the right key for join*/).through("topic3");
> stream4 = stream2.map(/* set the right key for join*/).through("topic4");
> stream3.join(stream4, ..)
> {code}
> This pattern can actually be done by the Streams DSL itself instead of requiring users to specify themselves, i.e. users can just set the right key like (see KAFKA-3430) and then call join, which will be translated by adding the "internal topic for repartition".
> Another thing is that today if user do not call "through" after setting a new key, the aggregation result would not be correct as the aggregation is based on key B while the source partitions is partitioned by key A and hence each task will only get a partial aggregation for all keys. But this is not validated in the DSL today. We should do both the auto-translation and validation.
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