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https://issues.apache.org/jira/browse/KAFKA-19484?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kamal Chandraprakash resolved KAFKA-19484.
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Fix Version/s: 4.2.0
Resolution: Fixed
> Tiered Storage Quota Metrics can stop reporting
> -----------------------------------------------
>
> Key: KAFKA-19484
> URL: https://issues.apache.org/jira/browse/KAFKA-19484
> Project: Kafka
> Issue Type: Bug
> Components: Tiered-Storage
> Affects Versions: 3.9.0, 4.0.0
> Environment: Ubuntu 22, Amazon Corretto Java 17
> Reporter: George Wu
> Priority: Minor
> Fix For: 4.2.0
>
>
> It is possible for tiered storage throttle metrics (introduced as a part of
> [KIP-956|https://cwiki.apache.org/confluence/display/KAFKA/KIP-956+Tiered+Storage+Quotas])
> to stop reporting if the relevant tiered storage operation (copy/fetch) goes
> idle for longer than the sensor expiry timeout of one hour.
>
> RemoteLogManager maintains a static reference to the sensors used for metric
> reporting. This is a problem because the default sensor expiry time is one
> hour and there is nothing responsible for handling expired sensors. If the
> sensors expire, RemoteLogManager will continue producing metrics through it's
> static references to sensor objects that have already been cleaned up by the
> ExpireSensorTask.
>
> This issue tends to affect fetch metrics a lot more than copy metrics because
> the copy sensors don't go idle unless the topics stop being produced to. In
> contrast, the use case of backfilling from earliest offset using tiered
> storage is a pretty common use case.
>
> *Reproduction*
> * Generate some amount of tiered storage fetch traffic on a topic. Confirm
> the remote-fetch-throttle-time-avg/max metrics are being reported.
> * Remove the consumer workload that triggers the tiered storage fetch
> traffic. Wait for one hour (the sensor expiration period)
> * Generate some more tiered storage fetch traffic. The metric will no longer
> report.
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