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https://issues.apache.org/jira/browse/KAFKA-10134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17166038#comment-17166038
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Guozhang Wang commented on KAFKA-10134:
---------------------------------------
What I did not see from my local run is the following:
{code}
Join group failed with org.apache.kafka.common.errors.DisconnectException
{code}
Which indicates that the socket connecting to the brokers cannot be
established, and the consumer has to retry discovering (the same) broker, and
then re-connect to it, and somehow after one minute or two the issue goes away
itself. If you did not restart the broker during that time, then I can only
think of transient network issues..
Actually, could you try only patching the logback PR but not the 9011 PR (i.e.
let it to falls into busy loop) and upload the logs so I can also check what's
causing the busy loops as well?
> 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: 2.6.0, 2.5.1
>
> Attachments: 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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