Ansible - starting a task after cpu load is below 2.0

Question

I am trying to create a playbook where I want to perform a simple debug task after cpu load is below 2.0.

I have this so far in cpu-load.yml:

---
- name: Check CPU load and wait
  hosts: localhost
  gather_facts: yes
  
  tasks:
    - name: Check cpu load
      shell: uptime | awk -F 'load average:' '{print $2}' | awk -F ', ' '{print $1}'
      register: cpu_load
      
    - name: Wait until cpu load is bellow 2.0
      wait_for:
        timeout: 300
        delay: 10
        shell: Do something here
        msg: "cpu load is bellow 2.0"
      
    - name: Continue jobs
      debug:
        msg: "CPU load is bellow 2.0. Continue!!!"

Now I am not sure how to make the task wait for the cpu load to go bellow 2.0. Can you guys help?

Answer 1

You need to put an until loop around your "check cpu load" task:

- hosts: localhost
  gather_facts: false
  tasks:
    - name: Check cpu load
      shell: uptime | awk -F 'load average:' '{print $2}' | awk -F ', ' '{print $1}'
      register: cpu_load
      until: cpu_load.stdout|float < 2.0
      retries: 300
      delay: 1

    - name: Some other task
      debug:
        msg: hello world

This will wait up to five minutes (300 retries with a 1-second delay) for the load average to drop below 2.0.

---

There are probably better ways to get the current 1-minute CPU load; reading from /proc/loadavg may be easiest:

- hosts: localhost
  gather_facts: false
  tasks:
    - name: Check cpu load
      command: cat /proc/loadavg
      register: cpu_load
      until: cpu_load.stdout.split()|first|float < 2.0
      retries: 300
      delay: 1

    - name: Some other task
      debug:
        msg: hello world