Scheduling - Node Affinity

 

선호하는 노드를 설정하는 방법으로, nodeSelector 보다 확장된 Label Selector 기능을 지원한다.
types - requiredDuringSchedulingIgnoredDuringExecution / preferredDuringSchedulingIgnoredDuringExecution

affinity > nodeAffinity > ${type} > nodeSelectorTerms > matchExpression > {key/{values}/operator}

 

Q) How many labels exists on node01?

$  k describe no node01 | grep -i -A 5 label
Labels:             beta.kubernetes.io/arch=amd64
                    beta.kubernetes.io/os=linux
                    kubernetes.io/arch=amd64
                    kubernetes.io/hostname=node01
                    kubernetes.io/os=linux
Annotations:        flannel.alpha.coreos.com/backend-data: {"VNI":1,"VtepMAC":"62:4a:ba:d5:c3:63"}

A) 5

 

Q) What is the value set to the label key beta.kubernetes.io/arch on node01?

A) amd64

 

Q) Apply a label color=blue to node node01

$ k label no node01 color=blue
node/node01 labeled

 

Q) Create a new deployment named blue with the nginx image and 3 replicas.

$ k create deployment blue --image=nginx --replicas=3
deployment.apps/blue created

 

Q) Which nodes can the pods for the blue deployment be placed on?

$ k describe no controlplane | grep -i taints
Taints:             <none>

$ k describe no node01 | grep -i taints
Taints:             <none>

A) controlplane and node01

 

Q) Set Node Affinity to the deployment to place the pods on node01 only.

Name: blue
Replicas: 3
Image: nginx
NodeAffinity: requiredDuringSchedulingIgnoredDuringExecution
Key: color
value: blue

$ k edit deployment blue

      # spec > template > spec아래 추가
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
              - matchExpressions:
                - key: color
                  operator: In
                  values:
                  - blue

deployment.apps/blue edited

 

Q) Which nodes are the pods placed on now?

$ k get po -o wide
NAME                    READY   STATUS    RESTARTS   AGE   IP           NODE     NOMINATED NODE   READINESS GATES
blue-5659879b55-7d9zf   1/1     Running   0          85s   172.17.1.4   node01   <none>           <none>
blue-5659879b55-l6mmw   1/1     Running   0          84s   172.17.1.5   node01   <none>           <none>
blue-5659879b55-slr74   1/1     Running   0          83s   172.17.1.6   node01   <none>           <none>

A) node01

 

Q) Create a new deployment named red with the nginx image and 2 replicas, and ensure it gets placed on the controlplane node only.

Use the label key - node-role.kubernetes.io/control-plane - which is already set on the controlplane node.

Name: red
Replicas: 2
Image: nginx
NodeAffinity: requiredDuringSchedulingIgnoredDuringExecution=
Key: node-role.kubernetes.io/control-plane
Use the right operator

$ k create deploy red --image=nginx --replicas=2 --dry-run=client -o yaml > reddeploy.yaml

$ vi reddeploy.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: red
  name: red
spec:
  replicas: 2
  selector:
    matchLabels:
      app: red
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: red
    spec:
      containers:
      - image: nginx
        name: nginx
        resources: {}
      # affinity 추가
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
             - matchExpressions:
               - key: node-role.kubernetes.io/control-plane
                 operator: Exists
status: {}

$ k apply -f reddeploy.yaml 
deployment.apps/red created