process_cpu_count is no longer accurate in .NET Core 3.1

[amrmahdi]

Please see dotnet/runtime#622 for reference. Given that the cpu count is now reported as the number of cores on the node, not on the container, this metric is no longer accurate.

prometheus-net.DotNetRuntime/src/prometheus-net.DotNetRuntime/DotNetRuntimeStatsCollector.cs

Line 137 in 4ae6922

processorCount.Set(Environment.ProcessorCount);

[djluck]

Interesting stuff- thanks for creating this issue @amrmahdi. https://github.com/dotnet/coreclr/issues/26053 seems to suggest some future workaround (i.e. Environment.ProcessorQuota) but for now, there's not a lot that can be done.

[amrmahdi]

What if we detect that the process is running a container using DOTNET_RUNNING_IN_CONTAINER then read the CPU shares from /sys/fs/cgroup/cpu/cpu.shares ?

[amrmahdi]

Actually that is really not needed, since container_spec_cpu_shares counter already published this metric. So I guess if using .NET Core 3.1 one can update the grafana dashboard to use container_spec_cpu_shares instead of process_cpu_count .