Optimize Kubernetes CPU Resources with Ansible Playbooks

How to Assign CPU Resources to Kubernetes (K8s) or OpenShift (OCP) Containers and Pods with Ansible

Welcome to another episode of Ansible Pilot! I'm Luca Berton, and today I'll show you how to manage CPU resource allocation for containers and pods in Kubernetes (K8s) and OpenShift (OCP) using Ansible.

In Kubernetes and OpenShift, containers cannot exceed their configured CPU limits. If there's available CPU time, a container is guaranteed as much CPU as it requests. You can control this behavior using the resources field in your container's manifest. Specifically, resources:requests sets the amount of CPU the container is guaranteed, while resources:limits specifies the maximum amount of CPU the container can use.

See also: Deploy Kubernetes Resources with Ansible Playbook

Using Ansible for Kubernetes and OpenShift

Introduction to the k8s Module

Ansible provides the kubernetes.core.k8s module to manage Kubernetes (K8s) and OpenShift (OCP) resources. This module allows you to create, update, and delete various Kubernetes objects.

Key Parameters

• name: The name of the Kubernetes object. • namespace: The namespace in which the object resides. • api_version: The API version of the object (e.g., "v1"). • kind: The type of the object (e.g., Pod, Namespace). • state: Desired state of the object (e.g., present, absent, patched). • definition: A YAML or JSON definition of the object. • src: Path to a file containing the YAML or JSON definition. • template: A YAML or JSON template for the object. • validate: How to validate the resource definition against Kubernetes schema.

For detailed documentation, visit: • kubernetes.core.k8s • Kubernetes CPU Resource Management

Example Playbook

This playbook demonstrates how to create a namespace and a pod with CPU resource requests and limits. We will use the vish/stress image to simulate CPU load.

Playbook Code

Save the following YAML as ansible_playbook.yml:

---
- name: k8s CPU Resource Management Playbook
  hosts: localhost
  gather_facts: false
  connection: local
  vars:
    myproject: "cpu-example"
  tasks:
    - name: Create namespace
      kubernetes.core.k8s:
        kind: Namespace
        name: "{{ myproject }}"
        state: present
        api_version: v1
- name: Create Pod with CPU resources
      kubernetes.core.k8s:
        state: present
        definition:
          apiVersion: v1
          kind: Pod
          metadata:
            name: cpu-Playbook
            namespace: "{{ myproject }}"
          spec:
            containers:
              - name: cpu-Playbook-ctr
                image: vish/stress
                resources:
                  limits:
                    cpu: "1"
                  requests:
                    cpu: "0.5"
                args:
                  - -cpus
                  - "2"

Execution

Run the playbook using the following command:

ansible-playbook ansible_playbook.yml

Output

After running the playbook, you should see output similar to:

PLAY [k8s CPU Resource Management Playbook] ************************************************************************************
TASK [Create namespace] *******************************************************************************************************
changed: [localhost]
TASK [Create Pod with CPU resources] *******************************************************************************************
changed: [localhost]
PLAY RECAP ********************************************************************************************************************
localhost                  : ok=2    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Idempotency

Running the playbook again should yield:

PLAY [k8s CPU Resource Management Playbook] ************************************************************************************
TASK [Create namespace] *******************************************************************************************************
ok: [localhost]
TASK [Create Pod with CPU resources] *******************************************************************************************
ok: [localhost]
PLAY RECAP ********************************************************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Verification

• Before Execution

Check if the namespace exists:

  kubectl get namespace | grep cpu
  

For OpenShift:

  oc get namespace | grep cpu
  

• After Execution

Verify the namespace and pod:

  kubectl get namespace cpu-example
  kubectl get pod cpu-Playbook --namespace=cpu-example
  kubectl get pod cpu-Playbook --namespace=cpu-example --output=yaml
  

For OpenShift:

  oc get namespace cpu-example
  oc get pods --namespace=cpu-example
  oc get pod cpu-Playbook --namespace=cpu-example --output=yaml
  

Logs

To verify the pod's behavior, view its logs:

kubectl logs cpu-Playbook --namespace=cpu-example

See also: Assign Memory to Kubernetes Pods with Ansible

Conclusion

You've now learned how to use Ansible to manage CPU resources for containers and pods in Kubernetes and OpenShift. This method allows you to ensure efficient resource allocation and management, enhancing the performance and stability of your applications.

Feel free to explore additional configurations and options to tailor your resource management to your specific needs. Thanks for joining this episode of Ansible Pilot, and happy automating!

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