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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
Output:
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 PriorityClass
.
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.