[jira] [Created] (KAFKA-12972) KStreams - Rebalance not happening

["NEERAJ VAIDYA (Jira)" <ji...@apache.org>]

NEERAJ VAIDYA created KAFKA-12972:
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             Summary: KStreams - Rebalance not happening
                 Key: KAFKA-12972
                 URL: https://issues.apache.org/jira/browse/KAFKA-12972
             Project: Kafka
          Issue Type: Bug
          Components: streams
    Affects Versions: 2.7.0
            Reporter: NEERAJ VAIDYA


I have a kafka streams application which consumes from a topic with 20 partitions.

I run the application with
{code:java}
num.streams.threads = 10
{code}
When I check the JMX MBean _kafka_consumer_coordinator_assigned_partitions_, I can see that each thread has been assigned 2 partitions. That sounds reasonable balancing of partitions across the threads.

Now, I add another instance of this application on a different machine/VM, but I run it with 4 stream threads.

I was expecting these 4 threads to be assigned (via rebalancing) atleast 1 partition each, but after multiple rebalancing schedules (every 10 mins), I do not see even 1 partition being assigned to any of these 4 threads in the second instance of my application.

I would have expected some rebalancing to happen across the 14 (10 + 4) stream threads of my application instances.

 



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