Affinity and AntiAffinity

亲和性分为NODE亲和性和POD亲和性

• requiredDuringSchedulingIgnoredDuringExecution 必须满足的条件
• preferredDuringSchedulingIgnoredDuringExecution 尽量满足的条件

Node亲和性

决定了一个POD能在哪些NODE节点上运行，取决于Node节点设置的标签

    spec:
      affinity:
        nodeAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
            - preference: {}
              weight: 100
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
              - matchExpressions:
                  - key: SC
                    operator: In
                    values:
                      - '1'

这里的含义就是这个POD必须运行在一个包含Key为SC并且Value为1的Node节点上.
反过来说就是如果一个Node节点的存在一个Key为SC并且Value为1的标签，那么这个node就能够跑POD.

Pod亲和性

相比较于Node的亲和性只能选择固定的节点，Pod的亲和性是针对运行在node节点上的pod来决定的.

    spec:
      affinity:
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
            - podAffinityTerm:
                labelSelector:
                  matchExpressions:
                    - key: app
                      operator: In
                      values:
                        - nginx
                topologyKey: kubernetes.io/hostname
              weight: 100

这里(In)的含义是如果一个node上存在一个 app=nginx 标签的POD，那么后续的POD尽量不要放在这个节点.
NotIn反之:如果一个node上存在app=nginx 标签的POD，那么后续的POD尽量放在这个节点

topologyKey

拓扑域

附录

• nginx#YAML文件

  apiVersion: apps/v1
  kind: Deployment
  metadata:
  labels:
    app: nginx
  name: nginx-deployment-basic
  namespace: default
  spec:
  progressDeadlineSeconds: 600
  replicas: 1
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: nginx
  strategy:
    rollingUpdate:
      maxSurge: 25%
      maxUnavailable: 25%
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - image: 'nginx:1.7.9'
          imagePullPolicy: IfNotPresent
          name: nginx
          ports:
            - containerPort: 80
              protocol: TCP
          readinessProbe:
            failureThreshold: 3
            httpGet:
              path: /
              port: 80
              scheme: HTTP
            initialDelaySeconds: 10
            periodSeconds: 10
            successThreshold: 1
            timeoutSeconds: 1
          resources: {}
          terminationMessagePath: /dev/termination-log
          terminationMessagePolicy: File
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {}
      terminationGracePeriodSeconds: 30