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https://issues.apache.org/jira/browse/KAFKA-9339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17011751#comment-17011751
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Ismael Juma commented on KAFKA-9339:
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No plans to drop support for Java 8 at the moment, but Java 11 makes it easier
to diagnose issues like this given the built-in flight recorder. This should
change once OpenJDK 8 gets it too:
[https://www.i-programmer.info/news/80-java/13279-openjdk-8-to-get-jdk-flight-recorder.html]
> Increased CPU utilization in brokers in 2.4.0
> ---------------------------------------------
>
> Key: KAFKA-9339
> URL: https://issues.apache.org/jira/browse/KAFKA-9339
> Project: Kafka
> Issue Type: Bug
> Affects Versions: 2.4.0
> Environment: CentOS 6; Java 1.8.0_232 (OpenJDK)
> Reporter: James Brown
> Priority: Minor
>
> I upgraded one of my company's test clusters from 2.3.1 to 2.4.0 and have
> noticed a significant (40%) increase in the CPU time consumed. This is a
> small cluster of three nodes (running on t2.large EC2 instances all in the
> same AZ) pushing about 150 message/s in aggregate spread across 208 topics (a
> total of 266 partitions; most topics only have one partition). Leadership is
> reasonably well-distributed and each node has between 83 and 94 partitions
> which it leads. This CPU time increase is visible symmetrically on all three
> nodes in the cluster (e.g., the controller isn't using more CPU than the
> other nodes).
>
> The CPU consumption did not return to normal after I did the second restart
> to bump the log and inter-broker protocol versions to 2.4, so I don't think
> it has anything to do with down-converting to the 2.3 protocols.
>
> No settings were changed, nor was anything about the JVM changed. There is
> nothing interesting being written to the logs. There's no sign of any
> instability (partitions aren't being reassigned, etc).
>
> The best guess I have for the increased CPU usage is that the number of
> garbage collections increased by approximately 30%, suggesting that something
> is churning a lot more garbage inside Kafka. This is a small cluster, so it's
> only got a 3GB heap allocated to Kafka on each node; we're using G1GC with
> some light tuning and are on Java 8 if that helps.
>
> We are only using OpenJDK, so I don't think I can produce a Flight Recorder
> profile.
>
> The kafka-users mailing list suggested this was worth filing a Jira issue
> about.
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