[jira] [Updated] (KAFKA-19606) Anomaly of JMX metrics RequestHandlerAvgIdlePercent in kraft combined mode

["José Armando García Sancio (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-19606?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

José Armando García Sancio updated KAFKA-19606:
-----------------------------------------------
    Fix Version/s: 4.2.0

> Anomaly of JMX metrics RequestHandlerAvgIdlePercent in kraft combined mode
> --------------------------------------------------------------------------
>
>                 Key: KAFKA-19606
>                 URL: https://issues.apache.org/jira/browse/KAFKA-19606
>             Project: Kafka
>          Issue Type: Bug
>          Components: core
>            Reporter: tony tang
>            Assignee: tony tang
>            Priority: Major
>             Fix For: 4.2.0
>
>         Attachments: Screenshot 2025-08-14 at 12.41.42.png
>
>
> JMX metrics RequestHandlerAvgIdlePercent reports a value close to 2 in combined kraft mode but it's expected to be b/w 0 and 1.
> This is an issue with combined mode specifically because both controller + broker are using the same Meter object in combined mode, defined in {{{}RequestThreadIdleMeter#requestThreadIdleMeter{}}}, but the controller and broker are using separate {{KafkaRequestHandlerPool}} objects, where each object's {{{}threadPoolSize == KafkaConfig.numIoThreads{}}}. This means when calculating idle time, each pool divides by its own {{numIoThreads}} value before reporting to the shared meter and  {{RequestHandlerAvgIdlePercent}} calculates the final result by accumulating all the values reported by all threads. However, since there are actually 2 × numIoThreads total threads contributing to the metric, the denominator should be doubled to get the correct average.



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