k8s 亲和性与反亲和性

转载自：https://blog.csdn.net/jettery/article/details/79003562

现实中应用的运行对于kubernetes在亲和性上提出了一些要求，可以归类到以下几个方面：
1.Pod固定调度到某些节点之上
2.Pod不会调度到某些节点之上
3.Pod的多副本调度到相同的节点之上
4.Pod的多副本调度到不同的节点之上

实践

Pod调动到某些节点上

Pod的定义中通过nodeSelector指定label标签，pod将会只调度到具有该标签的node之上

apiVersion: v1
kind: Pod
metadata:
  name: nginx
  labels:
    env: test
spec:
  containers:
  - name: nginx
    image: nginx
    imagePullPolicy: IfNotPresent
  nodeSelector:
    disktype: ssd

这个例子中pod只会调度到具有disktype=ssd的node上面．

Affinity/anti-affinity node

Affinity/anti-affinity node 相对于nodeSelector机制更加的灵活和丰富
requiredDuringSchedulingIgnoredDuringExecution表示必须满足亲和性配置；
preferredDuringSchedulingIgnoredDuringExecution表示优先选择满足亲和性配置，无法满足时会选择非nodeSelector 的节点。

topologyKey可以设置成如下几种类型
kubernetes.io/hostname　　＃Node
failure-domain.beta.kubernetes.io/zone　＃Zone
failure-domain.beta.kubernetes.io/region #Region
可以设置node上的label的值来表示node的name,zone,region等信息，pod的规则中指定topologykey的值表示指定topology范围内的node上运行的pod满足指定规则

例1：不会选择已经运行了label为app:store的pod的节点，而且3个副本不会运行在相同的节点上(topologyKey: "kubernetes.io/hostname")。

apiVersion: apps/v1beta1 # for versions before 1.6.0 use extensions/v1beta1
kind: Deployment
metadata:
  name: redis-cache
spec:
  replicas: 3
  template:
    metadata:
      labels:
        app: store
    spec:
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - store
            topologyKey: "kubernetes.io/hostname"
      containers:
      - name: redis-server
        image: redis:3.2-alpine

例2：在一些应用中，pod副本之间需要共享cache,需要将pod运行在一个节点之上

apiVersion: apps/v1beta1 # for versions before 1.6.0 use extensions/v1beta1
kind: Deployment
metadata:
  name: web-server
spec:
  replicas: 3
  template:
    metadata:
      labels:
        app: web-store
    spec:
      affinity:
        podAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - web-store
            topologyKey: "kubernetes.io/hostname"
      containers:
      - name: web-app
        image: hub.easystack.io/library/nginx:1.9.0

最后编辑于：2019.08.17 16:18:54