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https://issues.apache.org/jira/browse/KAFKA-12431?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17297989#comment-17297989
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Rajini Sivaram commented on KAFKA-12431:
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I can't think of any changes in 2.5.x or 2.6.x that explains this behaviour.
Looking at the code, I think we don't handle arithmetic overflows. So zero
quota may happen to result in no quota enforcement as a result of overflows
that set throttleTimeMs to a negative value. But this code doesn't seem to have
changed much since the older versions. Empty fetch response for quota violation
was introduced in 2.0.0 under KIP-219. In 2.6.0, we improved on this by sending
partial responses under KAFKA-9677. That may not help with very low quotas,
but shouldn't have caused any degradation compared to before. In any case, this
shouldn't have altered the handling of quota=0.
> Fetch Request/Response without Topic information
> ------------------------------------------------
>
> Key: KAFKA-12431
> URL: https://issues.apache.org/jira/browse/KAFKA-12431
> Project: Kafka
> Issue Type: Bug
> Affects Versions: 2.6.1
> Reporter: Peter Sinoros-Szabo
> Priority: Major
> Attachments: fetch-on-2.4.1.png, fetch-on-2.6.1.png,
> kafka-highcpu-24.svg.zip, kafka-highcpu-26.svg.zip
>
>
> I was running a 6 node Kafka 2.4.1 cluster with protocol and message format
> version set to 2.4. I wanted to upgrade the cluster to 2.6.1 and after I
> upgraded the 1st broker to 2.6.1 without any configuration change, I noticed
> much higher CPU usage on that broker (instead of 25% CPU usage it was ~350%)
> and about 3-4x higher network traffic. So I dumped the traffic between the
> Kafka client and broker and compared it with the traffic of the same broker
> downgraded to 2.4.1.
> It seems to me that after I upgraded to 2.6.1, the Fetch requests and
> responses are not complete, it is missing the topics part of the Fetch
> Request, I don't know for what reason. I guess there should be always a
> topics part.
> I'll attache a screenshot from these messages.
>
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