[cka] Node Affinity

 

Node Affinity란?

 

파드를 특정 노드나 노드 그룹에 스케줄링하는 방법을 제공합니다.

이는 스케줄링 제약 조건을 정의하는 데 사용되며, Node Affinity는 nodeSelector, requiredDuringSchedulingIgnoredDuringExecution, 및 preferredDuringSchedulingIgnoredDuringExecution과 같은 다양한 방법을 통해 설정할 수 있습니다.

 

1. How many Labels exist on node node01?

$ controlplane ~ ✖ k describe nodes node01
Name:               node01
Roles:              <none>
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":"2e:55:e7:36:8e:8a"}
                    flannel.alpha.coreos.com/backend-type: vxlan
                    flannel.alpha.coreos.com/kube-subnet-manager: true
                    flannel.alpha.coreos.com/public-ip: 192.24.223.3
                    kubeadm.alpha.kubernetes.io/cri-socket: unix:///var/run/containerd/containerd.sock
                    node.alpha.kubernetes.io/ttl: 0
                    volumes.kubernetes.io/controller-managed-attach-detach: true

answer : 5

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

answer : amd64

3. Apply a label color=blue to node node01

 

$ controlplane ~ ➜  k label node node01 color=blue
node/node01 labeled

 

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

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

 

5. Which nodes can the pods for the blue deployment be placed on?
Make sure to check taints on both nodes!

$ controlplane ~ ➜  k get pods -o wide
NAME                    READY   STATUS    RESTARTS   AGE   IP           NODE           NOMINATED NODE   READINESS GATES
blue-747bd9c977-6gqdm   1/1     Running   0          43s   10.244.0.4   controlplane   <none>           <none>
blue-747bd9c977-jhfwz   1/1     Running   0          43s   10.244.1.2   node01         <none>           <none>
blue-747bd9c977-p6gsx   1/1     Running   0          43s   10.244.1.3   node01         <none>           <none>

answer : controlplane and node01

 

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

https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/#node-affinity

Assigning Pods to Nodes

 

apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: blue
  name: blue
spec:
  replicas: 3
  selector:
    matchLabels:
      app: blue
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: blue
    spec:
      containers:
      - image: nginx
        name: nginx
        resources: {}
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: color
                operator: In
                values:
                  - blue

 

7. Which nodes are the pods placed on now?

 

$ controlplane ~ ➜  k get pods -o wide
NAME                   READY   STATUS    RESTARTS   AGE    IP           NODE     NOMINATED NODE   READINESS GATES
blue-8b4fdbcb5-64f5g   1/1     Running   0          104s   10.244.1.5   node01   <none>           <none>
blue-8b4fdbcb5-lxx5k   1/1     Running   0          102s   10.244.1.6   node01   <none>           <none>
blue-8b4fdbcb5-pvzph   1/1     Running   0          106s   10.244.1.4   node01   <none>           <none>

 

answer : node01

 

8. 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.

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
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: node-role.kubernetes.io/control-plane
                operator: Exists
status: {}