Pod Priority is used to apply importance of a pod relative to other pods. In this section we will create two
PriorityClass objects and watch the interaction of pods.
We will create two
PriorityClass objects, low-priority and high-priority.
cat <<EoF > ~/environment/resource-management/high-priority-class.yml apiVersion: scheduling.k8s.io/v1 kind: PriorityClass metadata: name: high-priority value: 100 globalDefault: false description: "High-priority Pods" EoF kubectl apply -f ~/environment/resource-management/high-priority-class.yml cat <<EoF > ~/environment/resource-management/low-priority-class.yml apiVersion: scheduling.k8s.io/v1 kind: PriorityClass metadata: name: low-priority value: 50 globalDefault: false description: "Low-priority Pods" EoF kubectl apply -f ~/environment/resource-management/low-priority-class.yml
Pods with without a
PriorityClass are 0. A global
PriorityClass can be assigned. Additional details can be found here
Next we will deploy low-priority pods to use up resources on the nodes. The goal is to saturate the nodes with as many pods as possible.
cat <<EoF > ~/environment/resource-management/low-priority-deployment.yml apiVersion: apps/v1 kind: Deployment metadata: labels: app: nginx-deployment name: nginx-deployment spec: replicas: 50 selector: matchLabels: app: nginx-deployment template: metadata: labels: app: nginx-deployment spec: priorityClassName: "low-priority" containers: - image: nginx name: nginx-deployment resources: limits: memory: 128Mi EoF kubectl apply -f ~/environment/resource-management/low-priority-deployment.yml
Watch the number of available pods in the
Deployment until the available stabilizes around a number. This exercise does not require all pods in the deployment to be in Available state. We want to ensure the nodes are completely filled with pods. It may take up to 2 minutes to stabilize.
kubectl get deployment nginx-deployment --watch
In a new terminal watch
Deployment using the command below
kubectl get deployment --watch
Next deploy high-priority
Deployment to see the how Kubernetes handles
cat <<EoF > ~/environment/resource-management/high-priority-deployment.yml apiVersion: apps/v1 kind: Deployment metadata: labels: app: high-nginx-deployment name: high-nginx-deployment spec: replicas: 5 selector: matchLabels: app: high-nginx-deployment template: metadata: labels: app: high-nginx-deployment spec: priorityClassName: "high-priority" containers: - image: nginx name: high-nginx-deployment resources: limits: memory: 128Mi EoF kubectl apply -f ~/environment/resource-management/high-priority-deployment.yml
What changes did you see?
kubectl get deployment --watch NAME READY UP-TO-DATE AVAILABLE AGE nginx-deployment 24/50 50 24 21s high-nginx-deployment 0/5 0 0 0s high-nginx-deployment 0/5 0 0 0s high-nginx-deployment 0/5 0 0 0s nginx-deployment 23/50 49 23 52s nginx-deployment 23/50 50 23 52s high-nginx-deployment 0/5 5 0 0s nginx-deployment 22/50 49 22 52s nginx-deployment 21/50 49 21 52s nginx-deployment 20/50 49 20 52s nginx-deployment 19/50 49 19 52s nginx-deployment 19/50 50 19 52s high-nginx-deployment 1/5 5 1 32s high-nginx-deployment 2/5 5 2 32s high-nginx-deployment 3/5 5 3 33s high-nginx-deployment 4/5 5 4 34s high-nginx-deployment 5/5 5 5 35s
When the higher-priority deployment is created, it started to remove lower-priority pods on the nodes.