CPU % - cgroup - container

What it does

This metric provider calculates an estimate of the % total CPU usage based on the cgroups stats file of your docker containers. More information about cgroups can be found here.

Classname

  • CpuUtilizationCgroupContainerProvider

Metric Name

  • cpu_utilization_cgroup_container

Input Parameters

  • args
    • -s: container-ids seperated by commas
    • -i: interval in milliseconds

By default the measurement interval is 100 ms.

./metric-provider-binary -i 100 -s 7f38a4c25fb8f9d5f8651d6ed986b3658dba20d1f5fec98a1f71c141c2b48f4b,c3592e1385d63f9c7810470b12aa00f7d6f7c0e2b9981ac2bdb4371126a0660a

Output

This metric provider prints to Stdout a continuous stream of data. The format of the data is as follows:

TIMESTAMP READING CONTAINER-ID

Where:

  • TIMESTAMP: Unix timestamp, in microseconds
  • READING: The estimated % CPU used
  • CONTAINER-ID: The container ID that this reading is for

Any errors are printed to Stderr.

How it works

The provider assumes that you have cgroups v2 enabled on your system

The provider reads from two files. To get the number of microseconds spent in the CPU by the container, during the interval, it reads from:

/sys/fs/cgroup/user.slice/user-<USER-ID>.slice/user@<USER-ID>.service/user.slice/docker-<CONTAINER-ID>.scope/cpu.stat

To get the total time spent by the cpu during that time interval, in Jiffies, you read from /proc/stat. We collect user, nice, system, idle iowait, irq, softirq, steal (see definitions here), add them together, divide by SC_CLK_TCK (typically 100 Hz). The percentage of the cgroup time divided by this sum is the total percentage of CPU time spent by the container.

Then it calculates the % cpu used via this formula: container_reading * 10000 / main_cpu_reading

In order to work in rootless cgroup delegation must be enabled here: /etc/systemd/system/[email protected]/delegate.conf

Currently, <USER-ID> is set to the calling user.

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CPU Time - procfs - system →