Assign Pods to Nodes using Node Affinity
This page shows how to assign a Kubernetes Pod to a particular node using Node Affinity in a Kubernetes cluster.
Before you begin
You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:
Your Kubernetes server must be at or later than version v1.10. To check the version, enter kubectl version
.
Add a label to a node
List the nodes in your cluster, along with their labels:
kubectl get nodes --show-labels
The output is similar to this:
NAME STATUS ROLES AGE VERSION LABELS
worker0 Ready <none> 1d v1.13.0 ...,kubernetes.io/hostname=worker0
worker1 Ready <none> 1d v1.13.0 ...,kubernetes.io/hostname=worker1
worker2 Ready <none> 1d v1.13.0 ...,kubernetes.io/hostname=worker2
Chose one of your nodes, and add a label to it:
kubectl label nodes <your-node-name> disktype=ssd
where
<your-node-name>
is the name of your chosen node.Verify that your chosen node has a
disktype=ssd
label:kubectl get nodes --show-labels
The output is similar to this:
NAME STATUS ROLES AGE VERSION LABELS
worker0 Ready <none> 1d v1.13.0 ...,disktype=ssd,kubernetes.io/hostname=worker0
worker1 Ready <none> 1d v1.13.0 ...,kubernetes.io/hostname=worker1
worker2 Ready <none> 1d v1.13.0 ...,kubernetes.io/hostname=worker2
In the preceding output, you can see that the
worker0
node has adisktype=ssd
label.
Schedule a Pod using required node affinity
This manifest describes a Pod that has a requiredDuringSchedulingIgnoredDuringExecution
node affinity,disktype: ssd
. This means that the pod will get scheduled only on a node that has a disktype=ssd
label.
pods/pod-nginx-required-affinity.yaml
apiVersion: v1
kind: Pod
metadata:
name: nginx
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: disktype
operator: In
values:
- ssd
containers:
- name: nginx
image: nginx
imagePullPolicy: IfNotPresent
Apply the manifest to create a Pod that is scheduled onto your chosen node:
kubectl apply -f https://k8s.io/examples/pods/pod-nginx-required-affinity.yaml
Verify that the pod is running on your chosen node:
kubectl get pods --output=wide
The output is similar to this:
NAME READY STATUS RESTARTS AGE IP NODE
nginx 1/1 Running 0 13s 10.200.0.4 worker0
Schedule a Pod using preferred node affinity
This manifest describes a Pod that has a preferredDuringSchedulingIgnoredDuringExecution
node affinity,disktype: ssd
. This means that the pod will prefer a node that has a disktype=ssd
label.
pods/pod-nginx-preferred-affinity.yaml
apiVersion: v1
kind: Pod
metadata:
name: nginx
spec:
affinity:
nodeAffinity:
preferredDuringSchedulingIgnoredDuringExecution:
- weight: 1
preference:
matchExpressions:
- key: disktype
operator: In
values:
- ssd
containers:
- name: nginx
image: nginx
imagePullPolicy: IfNotPresent
Apply the manifest to create a Pod that is scheduled onto your chosen node:
kubectl apply -f https://k8s.io/examples/pods/pod-nginx-preferred-affinity.yaml
Verify that the pod is running on your chosen node:
kubectl get pods --output=wide
The output is similar to this:
NAME READY STATUS RESTARTS AGE IP NODE
nginx 1/1 Running 0 13s 10.200.0.4 worker0
What’s next
Learn more about Node Affinity.