[jira] [Created] (KAFKA-3862) Kafka streams documentation: partition<->thread<->task assignment unclear

["Dmitry Minkovsky (JIRA)" <ji...@apache.org>]

Dmitry Minkovsky created KAFKA-3862:
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             Summary: Kafka streams documentation: partition<->thread<->task assignment unclear
                 Key: KAFKA-3862
                 URL: https://issues.apache.org/jira/browse/KAFKA-3862
             Project: Kafka
          Issue Type: Bug
          Components: streams
    Affects Versions: 0.10.0.0
         Environment: N/A
            Reporter: Dmitry Minkovsky
            Assignee: Guozhang Wang
            Priority: Minor


Hi. Not sure if this is the right place to post about documentation (this isn't actually a software bug).

I believe the following span of documentation is self-contradictory:

!http://i.imgur.com/WM8ada2.png!

In the paragraph text before and after the image, it says the partitions are *evenly distributed* among the threads. However, in the image, Thread 1 gets p1 and p3 (4 partitions, total) while Thread 2 gets p2 (2 partitions, total). That's "even" in the sense that you can't do any better, but still not even, and in conflict with the text that follows the image:

!http://i.imgur.com/xq3SOre.png!

This doesn't make sense because why would p2 from topicA and topicB go to different threads? if this were the cause, you couldn't join the partitions, right?

Either way, it seems like the two things are in conflict.

Finally, the wording:

bq. ...assume that each thread executes a single stream task...

What does "assume" mean here. I've not seen any indication elsewhere in the documentation that show you can configure this behavior. Sorry if I missed this.

Thank you!




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