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https://issues.apache.org/jira/browse/KAFKA-6468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16336969#comment-16336969
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ASF GitHub Bot commented on KAFKA-6468:
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ambroff opened a new pull request #4468: KAFKA-6468 Read
replication-offset-checkpoint once
URL: https://github.com/apache/kafka/pull/4468
Only read the high watermark checkpoint
file (replication-offset-checkpoint) once. Before this patch, this file
is read every time the broker handles LeaderAndIsrRequest. See
kafka.cluster.Partition#getOrCreateReplica(Int, Boolean).
On my local test cluster of three brokers with around 40k partitions,
the initial LeaderAndIsrRequest refers to every partition in the
cluster, and it can take 20 to 30 minutes to create all of the replicas
because the replication-offset-checkpoint is nearly 2MB.
Changing this code so that we only read this file once on startup
reduces the time to create all replicas to around one minute.
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*Summary of testing strategy (including rationale)
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### Committer Checklist (excluded from commit message)
- [ ] Verify design and implementation
- [ ] Verify test coverage and CI build status
- [ ] Verify documentation (including upgrade notes)
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> Replication high watermark checkpoint file read for every LeaderAndIsrRequest
> -----------------------------------------------------------------------------
>
> Key: KAFKA-6468
> URL: https://issues.apache.org/jira/browse/KAFKA-6468
> Project: Kafka
> Issue Type: Bug
> Reporter: Kyle Ambroff-Kao
> Assignee: Kyle Ambroff-Kao
> Priority: Major
>
> The high watermark for each partition in a given log directory is written to
> disk every _replica.high.watermark.checkpoint.interval.ms_ milliseconds. This
> checkpoint file is used to create replicas when joining the cluster.
> [https://github.com/apache/kafka/blob/b73c765d7e172de4742a3aa023d5a0a4b7387247/core/src/main/scala/kafka/cluster/Partition.scala#L180]
> Unfortunately this file is read every time
> kafka.cluster.Partition#getOrCreateReplica is invoked. For most clusters this
> isn't a big deal, but for a small cluster with lots of partitions all of the
> reads of this file really add up.
> On my local test cluster of three brokers with around 40k partitions, the
> initial LeaderAndIsrRequest refers to every partition in the cluster, and it
> can take 20 to 30 minutes to create all of the replicas because the
> _replication-offset-checkpoint_ is nearly 2MB.
> Changing this code so that we only read this file once on startup reduces the
> time to create all replicas to around one minute.
> Credit to [~onurkaraman] for finding this one.
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