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spring-bootspring-boot-actuatormicrometer

Relationship between SpringBoot actuator system.cpu.count metric and system.cpu.usage metric

Just would like to get some clarifications on the relationship between system.cpu.count metric and system.cpu.usage metric from SpringBoot 2.3.1 actuator metric endpoints.

For example, in my case:

The value of /actuator/metrics/system.cpu.count is: 2

The value of /actuator/metrics/system.cpu.usage is: 0.024765603908878

Does this mean that my cpu utilization percentage is: 0.024765603908878 / 2 * 100 = 1.24% ?

Solution

  • The metrics are provided in Spring Boot by Micrometer, specifically by Micrometer's ProcessorMetrics. Looking at its source, we can learn that system.cpu.count is backed by java.lang.Runtime.availableProcessors() and system.cpu.usage is backed by com.sun.management.OperatingSystemMXBean.getSystemCpuLoad(). Looking at those methods tells us that:

    • system.cpu.count is the number of CPUs that are available to the JVM.
    • system.cpu.usage is a value between 0.0 and 1.0 inclusive where a value of 0.0 means that all CPUs were idle during the recent period of time observed, while a value of 1.0 means that all CPUs were actively running 100% of the time during the recent period being observed.

    Your value of 0.025 indicates that CPU utilization was 2.5% of its total capacity. As you have two CPUs, this could be one CPU running at 5% and the other at 0%, both CPUs running at 2.5%, or any other combination in between.