节点亲和性分为强制选择(硬亲和)和优先选择(软亲和)：

• 强制选择requiredDuringSchedulingIgnoredDuringExecution
  • 满足则调度(案例一)
  • 不满足则Pending(案例二)
• 优先选择preferredDuringSchedulingIgnoredDuringExecution
  • 不满足则调度到其它节点(案例三)
  • 满足则优先调度到该节点，并不是一定调度到该节点，而且该节点优先级较高(案例四)

案例一

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deploy
spec:
  replicas: 5
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx-demo
        image: linuxmaxiaoke/nginx:v1.0.0
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: ssd
                operator: DoesNotExist
              - key: cpu
                operator: In
                values: ["high"]

[root@maxiaoke ~]# kubectl get pod -o wide # 不存在ssd标签，并且cpu值为 high
NAME                            READY   STATUS    RESTARTS   AGE   IP            NODE          NOMINATED NODE   READINESS GATES
nginx-deploy-6f8b6d748c-4pt2x   1/1     Running   0          8s    172.16.5.20   centos-7-56   <none>           <none>
nginx-deploy-6f8b6d748c-m9kb4   1/1     Running   0          8s    172.16.5.19   centos-7-56   <none>           <none>
nginx-deploy-6f8b6d748c-st8mw   1/1     Running   0          5s    172.16.5.22   centos-7-56   <none>           <none>
nginx-deploy-6f8b6d748c-w4mc9   1/1     Running   0          5s    172.16.5.21   centos-7-56   <none>           <none>
nginx-deploy-6f8b6d748c-wjvxx   1/1     Running   0          8s    172.16.5.18   centos-7-56   <none>           <none>

案例二

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deploy
spec:
  replicas: 5
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx-demo
        image: linuxmaxiaoke/nginx:v1.0.0
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: ssd
                operator: DoesNotExist
              # 此处改为cpu不等于high
              - key: cpu
                operator: NotIn
                values: ["high"]

[root@maxiaoke ~]# kubectl describe pod nginx-deploy-746f88c86-96dbp # 注意message
Name:           nginx-deploy-746f88c86-96dbp
Namespace:      default
Priority:       0
Node:           <none>
......
Status:         Pending
......
Events:
  Type     Reason            Age                From               Message
  ----     ------            ----               ----               -------
  Warning  FailedScheduling  30s (x3 over 32s)  default-scheduler  0/6 nodes are available: 3 node(s) didn't match node selector, 3 node(s) had taint {node-role.kubernetes.io/master: }, that the pod didn't tolerate.

案例三

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deploy
spec:
  replicas: 5
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx-demo
        image: linuxmaxiaoke/nginx:v1.0.0
      affinity:
        nodeAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - preference:
              matchExpressions:
                # 系统中并没有这个的Node
                - key: ssd
                  operator: DoesNotExist
                - key: cpu
                  operator: NotIn
                  values: ["high"]
            weight: 5

案例四

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deploy
spec:
  replicas: 5
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx-demo
        image: linuxmaxiaoke/nginx:v1.0.0
      affinity:
        nodeAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          # 满足该条件的节点为 centos-7-56,当并不是一把梭全部压在该节点，而且该节点的优先级更高，通过weight可以增加优先级
          - preference:
              matchExpressions:
              - key: ssd
                operator: DoesNotExist
              - key: cpu
                operator: In
                values:
                - high
            weight: 10

[root@maxiaoke local-k8s-yaml]# kubectl get pod -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP             NODE          NOMINATED NODE   READINESS GATES
nginx-deploy-5996df99f8-4cmfv   1/1     Running   0          7s    172.16.4.4     centos-7-55   <none>           <none>
nginx-deploy-5996df99f8-77k5l   1/1     Running   0          7s    172.16.5.38    centos-7-56   <none>           <none>
nginx-deploy-5996df99f8-8kxvc   1/1     Running   0          7s    172.16.5.37    centos-7-56   <none>           <none>
nginx-deploy-5996df99f8-t55hj   1/1     Running   0          7s    172.16.3.161   centos-7-54   <none>           <none>
nginx-deploy-5996df99f8-zbpf2   1/1     Running   0          7s    172.16.5.39    centos-7-56   <none>           <none>