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https://issues.apache.org/jira/browse/KAFKA-10134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17192513#comment-17192513
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Sophie Blee-Goldman commented on KAFKA-10134:
---------------------------------------------

Hey [~davispw],

It looks like you might have run into a few distinct issues: the rebalancing 
problems, the "insufficient bytes available" IllegalStateException, and the 
"Active task 3_0 should have been suspended" IllegalStateException.

The rebalancing seems to point to this issue, as the full fix did not make it 
into 2.6.0 in time. It would be great if you could test out the patch and see 
if that helps (building from 
[pull/8834|https://github.com/apache/kafka/pull/8834] specifically, which is 
not yet merged). The patch I linked also includes a fix for KAFKA-10122, 
another cause of unnecessary rebalances.

For the two IllegalStateException issues, could you open separate tickets? They 
seem unrelated to this, and to each other, but definitely merit a closer look. 
Any logs you have from the time of the exceptions would help a lot. 

Thanks!

> High CPU issue during rebalance in Kafka consumer after upgrading to 2.5
> ------------------------------------------------------------------------
>
>                 Key: KAFKA-10134
>                 URL: https://issues.apache.org/jira/browse/KAFKA-10134
>             Project: Kafka
>          Issue Type: Bug
>          Components: clients
>    Affects Versions: 2.5.0
>            Reporter: Sean Guo
>            Assignee: Guozhang Wang
>            Priority: Blocker
>             Fix For: 2.5.2, 2.6.1
>
>         Attachments: consumer3.log.2020-08-20.log, 
> consumer5.log.2020-07-22.log
>
>
> We want to utilize the new rebalance protocol to mitigate the stop-the-world 
> effect during the rebalance as our tasks are long running task.
> But after the upgrade when we try to kill an instance to let rebalance happen 
> when there is some load(some are long running tasks >30S) there, the CPU will 
> go sky-high. It reads ~700% in our metrics so there should be several threads 
> are in a tight loop. We have several consumer threads consuming from 
> different partitions during the rebalance. This is reproducible in both the 
> new CooperativeStickyAssignor and old eager rebalance rebalance protocol. The 
> difference is that with old eager rebalance rebalance protocol used the high 
> CPU usage will dropped after the rebalance done. But when using cooperative 
> one, it seems the consumers threads are stuck on something and couldn't 
> finish the rebalance so the high CPU usage won't drop until we stopped our 
> load. Also a small load without long running task also won't cause continuous 
> high CPU usage as the rebalance can finish in that case.
>  
> "executor.kafka-consumer-executor-4" #124 daemon prio=5 os_prio=0 
> cpu=76853.07ms elapsed=841.16s tid=0x00007fe11f044000 nid=0x1f4 runnable  
> [0x00007fe119aab000]"executor.kafka-consumer-executor-4" #124 daemon prio=5 
> os_prio=0 cpu=76853.07ms elapsed=841.16s tid=0x00007fe11f044000 nid=0x1f4 
> runnable  [0x00007fe119aab000]   java.lang.Thread.State: RUNNABLE at 
> org.apache.kafka.clients.consumer.internals.ConsumerCoordinator.poll(ConsumerCoordinator.java:467)
>  at 
> org.apache.kafka.clients.consumer.KafkaConsumer.updateAssignmentMetadataIfNeeded(KafkaConsumer.java:1275)
>  at 
> org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1241) 
> at 
> org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1216) 
> at
>  
> By debugging into the code we found it looks like the clients are  in a loop 
> on finding the coordinator.
> I also tried the old rebalance protocol for the new version the issue still 
> exists but the CPU will be back to normal when the rebalance is done.
> Also tried the same on the 2.4.1 which seems don't have this issue. So it 
> seems related something changed between 2.4.1 and 2.5.0.
>  



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