[jira] [Updated] (KAFKA-4875) Kafka Streams: topic groups and builder.stream API

["Eno Thereska (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-4875?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Eno Thereska updated KAFKA-4875:
--------------------------------
    Fix Version/s:     (was: 0.11.0.0)
                   0.11.1.0

> Kafka Streams: topic groups and builder.stream API
> --------------------------------------------------
>
>                 Key: KAFKA-4875
>                 URL: https://issues.apache.org/jira/browse/KAFKA-4875
>             Project: Kafka
>          Issue Type: Improvement
>          Components: streams
>    Affects Versions: 0.10.2.0
>            Reporter: Eno Thereska
>             Fix For: 0.11.1.0
>
>
> One thing that has come up in mailing list is that the notion of topic groups is unclear. So if you have 2 topics, each with 3 partitions, you'd expect 6 tasks. However, if you do `builder.stream(topic1, topic2)` you actually get only 3 tasks created. If you do `builder.stream(topic1); builder.stream(topic2)` you get 6 tasks, i.e., parallelism is increased. So the same application, calling builder.stream() in two different ways, might see different performance.
> In the Kafka Streams documentations we mention partitions and tasks, but not topic groups. We also do not document the effects of using builder.stream with a topic array. We also need to revisit whether the API and its effects are confusing.



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