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https://issues.apache.org/jira/browse/KAFKA-19652?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18024066#comment-18024066
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Jainil Rana edited comment on KAFKA-19652 at 12/11/25 4:03 AM:
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Hi [~gargsha] , [~mjsax] , I tried reproducing this, in 3.9.0 the consumer
throughput drops a lot (~250MB/s → ~90MB/s) when {{{}min.insync.replicas=2{}}}.
I noticed {{findPreferredReadReplica}} only picks from ISR. When followers drop
out, consumers end up reading only from the leader, which seems to cause the
slowdown.
Would it be safe to let consumers read from out-of-ISR followers if they have
the data (with HW checks), or is that too risky
was (Author: JIRAUSER310849):
Hi [~gargsha] , [~mjsax] , I tried reproducing this, in 3.9.0 the consumer
throughput drops a lot (~250MB/s → ~90MB/s) when {{{}min.insync.replicas=2{}}}.
I noticed {{findPreferredReadReplica}} only picks from ISR. When followers drop
out, consumers end up reading only from the leader, which seems to cause the
slowdown.
Would it be safe to let consumers read from out-of-ISR followers if they have
the data (with HW checks), or is that too risky?
> Consumer throughput drops by 10 times with Kafka v3.9.0 in ZK mode
> ------------------------------------------------------------------
>
> Key: KAFKA-19652
> URL: https://issues.apache.org/jira/browse/KAFKA-19652
> Project: Kafka
> Issue Type: Bug
> Components: clients, consumer
> Affects Versions: 3.9.0
> Reporter: Sharad Garg
> Assignee: Jainil Rana
> Priority: Blocker
>
> Kafka consumer throughput in best-case drops by ~10 times after upgrading to
> kafka v3.9.0 from v3.5.1. Note that this is in ZK mode and KRAFT migration is
> not done yet.
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