Pod priority and preemption in Kubernetes - Mini Project: Build & Apply

Pod Priority and Preemption in Kubernetes

📖 Scenario: You are managing a Kubernetes cluster where some applications are more important than others. You want to make sure that when resources are tight, the most important pods get scheduled first by using pod priority and preemption.

🎯 Goal: Learn how to create pod priority classes and assign priorities to pods so that Kubernetes can preempt lower priority pods when scheduling higher priority pods.

📋 What You'll Learn

Create a pod priority class with a specific priority value

Create a pod that uses the priority class

Create a lower priority pod

Observe pod scheduling and preemption behavior

💡 Why This Matters

🌍 Real World

Pod priority and preemption help ensure that critical applications get the resources they need in a busy Kubernetes cluster, improving reliability and user experience.

💼 Career

Understanding pod priority and preemption is essential for Kubernetes administrators and DevOps engineers to manage cluster resources effectively and maintain application uptime.

1

Create a Pod Priority Class

Create a pod priority class named high-priority with a value of 1000 and a globalDefault set to false. Use the kubectl apply -f command with a YAML manifest.

Kubernetes

# Write the YAML manifest for the high-priority pod priority class here
# Your code here

Need a hint?

Use kind: PriorityClass and set value to 1000.

2

Create a Pod with Lower Priority

Create a pod named low-priority-pod without specifying a priority class. The pod should run the nginx container. Use the kubectl apply -f command with a YAML manifest.

Kubernetes

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: high-priority
value: 1000
globalDefault: false
description: "High priority class for important pods"

# Write the YAML manifest for the low-priority-pod here
# Your code here

Need a hint?

Do not set priorityClassName for the low priority pod.

3

Create a Pod with High Priority

Create a pod named important-pod that uses the high-priority priority class. Use the kubectl apply -f command with a YAML manifest. The pod should run the nginx container.

Kubernetes

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: high-priority
value: 1000
globalDefault: false
description: "High priority class for important pods"
---
apiVersion: v1
kind: Pod
metadata:
  name: low-priority-pod
spec:
  containers:
  - name: nginx
    image: nginx

# Write the YAML manifest for the important-pod here
# Your code here

Need a hint?

Set priorityClassName to high-priority in the pod spec.

4

Observe Pod Scheduling and Preemption

Run kubectl get pods to see the status of the pods. Then run kubectl describe pod low-priority-pod to check if it was preempted when important-pod was scheduled.

Kubernetes

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: high-priority
value: 1000
globalDefault: false
description: "High priority class for important pods"
---
apiVersion: v1
kind: Pod
metadata:
  name: low-priority-pod
spec:
  containers:
  - name: nginx
    image: nginx
---
apiVersion: v1
kind: Pod
metadata:
  name: important-pod
spec:
  priorityClassName: high-priority
  containers:
  - name: nginx
    image: nginx

# Run the commands below to check pod status
# Your code here

Need a hint?

Use kubectl get pods and kubectl describe pod low-priority-pod to observe scheduling and preemption.