【模块一】kubernetes容器编排进阶实战之kubernetes pod Affinity与pod antiaffinity

news2025/1/4 8:17:53

pod Affinity与pod antiaffinity

Pod Affinity与anti-affinity简介：

Pod亲和性与反亲和性可以基于已经在node节点上运行的Pod的标签来约束新创建的Pod可以调度到的目的节点，注意不是基于node上的标签而是使用的已经运行在node上的pod标签匹配。
其规则的格式为如果 node节点 A已经运行了一个或多个满足调度新创建的Pod B的规则，那么新的 Pod B在亲和的条件下会调度到A节点之上，而在反亲和性的情况下则不会调度到A节点至上。
其中规则表示一个具有可选的关联命名空间列表的LabelSelector，只所以Pod亲和与反亲和需可以通过LabelSelector选择namespace，是因为Pod是命名空间限定的而node不属于任何nemespace所以 node的亲和与反亲和不需要namespace，因此作用于Pod标签的标签选择算符必须指定选择算符应用在哪个命名空间。
从概念上讲，node节点是一个拓扑域(具有拓扑结构的区域、宕机的时候的故障域)，比如k8s集群中的单台node节点、一个机架、云供应商可用区、云供应商地理区域等，可以使用topologyKey来定义亲和或者反亲和的颗粒度是node级别还是可用区级别，以便kubernetes调度系统用来识别并选择正确的目的拓扑域。

Pod 亲和性与反亲和性的合法操作符(operator)有 In、NotIn、Exists、DoesNotExist。
在Pod亲和性配置中，在requiredDuringSchedulingIgnoredDuringExecution和 preferredDuringSchedulingIgnoredDuringExecution中，topologyKey不允许为空(Empty topologyKey is not allowed.)。
在Pod反亲和性中配置中，requiredDuringSchedulingIgnoredDuringExecution和 preferredDuringSchedulingIgnoredDuringExecution 中，topologyKey也不可以为空(Empty topologyKey is not allowed.)。
对于requiredDuringSchedulingIgnoredDuringExecution要求的Pod反亲和性，准入控制器 LimitPodHardAntiAffinityTopology被引入以确保topologyKey只能是 kubernetes.io/hostname，如果希望 topologyKey 也可用于其他定制拓扑逻辑，可以更改准入控制器或者禁用。
除上述情况外，topologyKey 可以是任何合法的标签键。

case4-4.1：部署web服务

编写yaml文件，在magedu anmespace部署一个nginx服务，nginx pod将用于后续的pod 亲和及反亲和测试，且pod的label如下：
- app: python-nginx-selector
- project: python
部署nginx web服务：
- kubectl apply -f case4-4.1-nginx.yaml
  - deployment.apps/python-nginx-deployment created
  - service/python-nginx-service created

case4-4.2:Pod Affinity-软亲和：

基于软亲和实现多pod在一个node：先创建一个nginx服务,后续的服务和nginx运行在同一个node节点
- # kubectl apply -f case4-4.1-nginx.yaml
  - deployment.apps/python-nginx-deployment created
  - service/python-nginx-service created
实现软亲和pod调度：
- # kubectl apply -f case4-4.2-podaffinity-preferredDuring.yaml
  - deployment.apps/magedu-tomcat-app2-deployment created
验证pod调度结果：

[root@k8s-master1 Affinit-case]#cat case4-4.2-podaffinity-preferredDuring.yaml 
kind: Deployment
#apiVersion: extensions/v1beta1
apiVersion: apps/v1
metadata:
  labels:
    app: magedu-tomcat-app2-deployment-label
  name: magedu-tomcat-app2-deployment
  namespace: magedu
spec:
  replicas: 1
  selector:
    matchLabels:
      app: magedu-tomcat-app2-selector
  template:
    metadata:
      labels:
        app: magedu-tomcat-app2-selector
    spec:
      containers:
      - name: magedu-tomcat-app2-container
        image: tomcat:7.0.94-alpine
        imagePullPolicy: IfNotPresent
        #imagePullPolicy: Always
        ports:
        - containerPort: 8080
          protocol: TCP
          name: http
      affinity:
        podAffinity:  #Pod亲和
          #requiredDuringSchedulingIgnoredDuringExecution: #硬亲和，必须匹配成功才调度，如果匹配失败则拒绝调度。
          preferredDuringSchedulingIgnoredDuringExecution: #软亲和，能匹配成功就调度到一个topology，匹配不成功会由kubernetes自行调度。
          - weight: 100
            podAffinityTerm:
              labelSelector: #标签选择
                matchExpressions: #正则匹配
                - key: project
                  operator: In
                  values:
                    - pythonX
              topologyKey: kubernetes.io/hostname 
              namespaces:
                - magedu

case4-4.3:Pod Affinity-硬亲和

基于软亲和实现多pod在一个node：先创建一个nginx服务,后续的服务和nginx运行在同一个node节点
- root@k8s-master1:~/case/case# kubectl apply -f case4-4.1-nginx.yaml
  - deployment.apps/python-nginx-deployment created
  - service/python-nginx-service created
实现硬亲和pod调度：
- root@k8s-master1:~/case/case# kubectl apply -f case4-4.3-podaffinity-requiredDuring.yaml
  - deployment.apps/magedu-tomcat-app2-deployment created
验证pod调度结果：

[root@k8s-master1 Affinit-case]#cat case4-4.3-podaffinity-requiredDuring.yaml 
kind: Deployment
#apiVersion: extensions/v1beta1
apiVersion: apps/v1
metadata:
  labels:
    app: magedu-tomcat-app2-deployment-label
  name: magedu-tomcat-app2-deployment
  namespace: magedu
spec:
  replicas: 1
  selector:
    matchLabels:
      app: magedu-tomcat-app2-selector
  template:
    metadata:
      labels:
        app: magedu-tomcat-app2-selector
    spec:
      containers:
      - name: magedu-tomcat-app2-container
        image: tomcat:7.0.94-alpine
        imagePullPolicy: IfNotPresent
        #imagePullPolicy: Always
        ports:
        - containerPort: 8080
          protocol: TCP
          name: http
      affinity:
        podAffinity:
          requiredDuringSchedulingIgnoredDuringExecution: #硬亲和
          - labelSelector:
              matchExpressions:
              - key: project
                operator: In
                values:
                  - python
            topologyKey: "kubernetes.io/hostname"
            namespaces:
              - magedu

case4-4.4:podAntiAffinity-硬反亲和

基于硬反亲和实现多个pod调度不在一个node：先创建一个nginx服务,后续的服务和nginx运行不在同一个node节点
- root@k8s-master1:~/case/case# kubectl apply -f case4-4.1-nginx.yaml
  - deployment.apps/python-nginx-deployment created
  - service/python-nginx-service created
实现硬反亲和pod调度：
- kubectl apply -f case4-4.4-podAntiAffinity-requiredDuring.yaml
  - deployment.apps/magedu-tomcat-app2-deployment created
验证pod调度结果：

[root@k8s-master1 Affinit-case]#cat case4-4.4-podAntiAffinity-requiredDuring.yaml 
kind: Deployment
#apiVersion: extensions/v1beta1
apiVersion: apps/v1
metadata:
  labels:
    app: magedu-tomcat-app2-deployment-label
  name: magedu-tomcat-app2-deployment
  namespace: magedu
spec:
  replicas: 1
  selector:
    matchLabels:
      app: magedu-tomcat-app2-selector
  template:
    metadata:
      labels:
        app: magedu-tomcat-app2-selector
    spec:
      containers:
      - name: magedu-tomcat-app2-container
        image: tomcat:7.0.94-alpine
        imagePullPolicy: IfNotPresent
        #imagePullPolicy: Always
        ports:
        - containerPort: 8080
          protocol: TCP
          name: http
      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: project
                operator: In
                values:
                  - python
            topologyKey: "kubernetes.io/hostname"
            namespaces:
              - magedu

case4-4.5:podAntiAffinity-软反亲和：

基于软亲和实现多个pod调度不在一个node：先创建一个nginx服务,后续的服务和nginx运行不在同一个node节点
- root@k8s-master1:~/case/case# kubectl apply -f case4-4.1-nginx.yaml
  - deployment.apps/python-nginx-deployment created
  - service/python-nginx-service created
实现软亲和pod调度：
- root@k8s-master1:~/case/case# kubectl apply -f case4-4.5-podAntiAffinity-preferredDuring.yaml
  - deployment.apps/magedu-tomcat-app2-deployment created
验证pod调度结果：

[root@k8s-master1 Affinit-case]#cat case4-4.5-podAntiAffinity-preferredDuring.yaml 
kind: Deployment
#apiVersion: extensions/v1beta1
apiVersion: apps/v1
metadata:
  labels:
    app: magedu-tomcat-app2-deployment-label
  name: magedu-tomcat-app2-deployment
  namespace: magedu
spec:
  replicas: 20
  selector:
    matchLabels:
      app: magedu-tomcat-app2-selector
  template:
    metadata:
      labels:
        app: magedu-tomcat-app2-selector
    spec:
      containers:
      - name: magedu-tomcat-app2-container
        image: tomcat:7.0.94-alpine
        imagePullPolicy: IfNotPresent
        #imagePullPolicy: Always
        ports:
        - containerPort: 8080
          protocol: TCP
          name: http
      affinity:
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - weight: 100
            podAffinityTerm:
              labelSelector:
                matchExpressions:
                - key: project 
                  operator: In
                  values:
                    - python
              topologyKey: kubernetes.io/hostname 
              namespaces: 
                - magedu

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