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https://issues.apache.org/jira/browse/FLINK-39404?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yuepeng Pan updated FLINK-39404:
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Affects Version/s: 2.5.0
> HardwareDescription reports incorrect CPU cores in containerized environments
> with fractional CPU limits
> --------------------------------------------------------------------------------------------------------
>
> Key: FLINK-39404
> URL: https://issues.apache.org/jira/browse/FLINK-39404
> Project: Flink
> Issue Type: Bug
> Components: API / Core, Runtime / Metrics, Runtime / Task
> Affects Versions: 2.3.0, 2.5.0
> Reporter: Dennis-Mircea Ciupitu
> Priority: Major
> Labels: pull-request-available
> Fix For: 2.4.0
>
>
> When Flink runs inside a container with a fractional CPU limit (e.g. 0.5
> cores), the Web UI and REST API report an incorrect number of CPU cores. A
> TaskManager limited to 0.5 CPU cores is displayed as having 1 CPU core.
> {{Hardware.getNumberCPUCores()}} relies on
> {{{}Runtime.getRuntime().availableProcessors(){}}}, which returns an int. In
> containerized environments (Kubernetes, YARN), this value is the ceiling of
> the container’s CPU limit, so a limit of {{0.5}} cores is reported as
> {{{}1{}}}, and {{1.5}} cores is reported as {{{}2{}}}.
> Additionally, {{HardwareDescription.numberOfCPUCores}} is typed as
> {{{}int{}}}, which fundamentally cannot represent fractional CPU allocations.
> This causes two problems:
> # {*}Inaccurate Web UI display{*}: The Task Manager list and detail pages
> show rounded-up CPU cores (e.g. "1" instead of "0.5"), misleading operators
> about actual resource allocation.
> # {*}Thread pool over-provisioning{*}:
> {{ClusterEntrypointUtils.getPoolSize()}} computes {{{}4 *
> Hardware.getNumberCPUCores(){}}}. With {{0.5}} CPU, this creates {{4}}
> threads ({{{}4 * ceil(0.5) = 4 * 1 = 4{}}}) instead of the correct 2 threads
> ({{{}ceil(4 * 0.5) = 2{}}}).
> h3. Steps to Reproduce
> # Deploy a Flink cluster on Kubernetes with
> {{kubernetes.taskmanager.cpu.amount: 0.5}}
> # Open the Flink Web UI → Task Managers
> # Observe that "CPU Cores" shows *1* instead of *0.5*
> h3. Expected Behavior
> * The Task Manager Web UI should display *0.5* CPU cores
> * Thread pool sizing should use the fractional value before ceiling:
> {{ceil(4 * 0.5) = 2}} threads
> h3. Actual Behavior
> * The Web UI displays *1* CPU core
> * Thread pool sizing over-provisions: {{4 * ceil(0.5) = 4}} threads
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