关于K8S亲和性的解释

apiVersion: v1
kind: Pod
metadata:
  name: nodeaffinity #pod名称
  namespace: dev
spec:
  containers:
  - name: nginx
    image: nginx: latest
  affinity:  #亲和性设置
    nodeAffinity: #设置node亲和性
      requiredDuringSchedulingIgnoredDuringExecution: # 硬限制
        nodeSelectorTerms:
        - matchExpressions: # 匹配env的值在["aa","bb"]中的标签
          - key: nodeenv
            operator: In
            values: ["aa","bb"]

# 创建pod
[root@k8s-master01 ~]# kubectl create -f pod.yaml
pod/nodeaffinity created

# 查看pod状态 （运行失败）
[root@k8s-master01 ~]# kubectl get pods nodeaffinity -n dev -o wide
NAME                        READY   STATUS    RESTARTS   AGE   IP       NODE    ...... 
nodeaffinity   0/1     Pending   0          6s   <none>   <none>  ......

# 查看Pod的详情
# 发现调度失败，提示node选择失败
[root@k8s-master01 ~]# kubectl describe pod nodeaffinity -n dev
......


#接下来，停止pod
[root@k8s-master01 ~]# kubectl delete -f pod.yaml
pod "nodeaffinity" deleted

# 修改文件，将values: ["aa","bb"]------> ["pro","pod"]
[root@k8s-master01 ~]# vim pod.yaml

# 再次启动
[root@k8s-master01 ~]# kubectl create -f pod.yaml
pod/nodeaffinity created

# 此时查看，发现调度成功，已经将pod调度到了node1上
[root@k8s-master01 ~]# kubectl get pods nodeaffinity -n dev -o wide
NAME                        READY   STATUS    RESTARTS   AGE   IP            NODE  ...... 
nodeaffinity  1/1     Running   0          11s   10.200.1.9   node1 ......

apiVersion: v1
kind: Pod
metadata:
  name: nodeaffinity
  namespace: dev
spec:
  containers:
  - name: nginx
    image: nginx:latest
  affinity:  #亲和性设置
    nodeAffinity: #设置node亲和性
      preferredDuringSchedulingIgnoredDuringExecution: # 软限制 优先匹配设定的规则，没有匹配也可以运行
      - weight: 1
        preference:
          matchExpressions: # 匹配env的值在["dev","test"]中的标签(当前环境没有)
          - key: nodeenv
            operator: In
            values: ["dev","test"]

# 创建pod
[root@k8s-master01 ~]# kubectl create -f pod.yaml
pod/nodeaffinity created

# 查看pod状态 （运行成功），即使没有这样标签的node
[root@k8s-master01 ~]# kubectl get pod nodeaffinity -n dev
NAME                         READY   STATUS    RESTARTS   AGE
nodeaffinity  1/1     Running   0          40s

NodeAffinity规则设置的注意事项：
    1 如果同时定义了nodeSelector和nodeAffinity，那么必须两个条件都得到满足，Pod才能运行在指定的Node上
    2 如果nodeAffinity指定了多个nodeSelectorTerms，那么只需要其中一个能够匹配成功即可
    3 如果一个nodeSelectorTerms中有多个matchExpressions ，则一个节点必须满足所有的才能匹配成功
    4 如果一个pod所在的Node在Pod运行期间其标签发生了改变，不再符合该Pod的节点亲和性需求，则系统将忽略此变化

apiVersion: v1
kind: Pod
metadata:
  name: pod-target
  namespace: dev
  labels:
    podenv: pro #设置标签
spec:
  containers:
  - name: nginx
    image: nginx: latest
  nodeName: node1 # 将目标pod名确指定到node1上

# 启动目标pod
[root@k8s-master01 ~]# kubectl create -f pod-target.yaml
pod/pod-target created

# 查看pod状况
[root@k8s-master01 ~]# kubectl get pods  pod-target -n dev
NAME                     READY   STATUS    RESTARTS   AGE
pod-target   1/1     Running   0          4s

apiVersion: v1
kind: Pod
metadata:
  name: pod-podaffinity-required
  namespace: dev
spec:
  containers:
  - name: nginx
    image: nginx: latest
  affinity:  #亲和性设置
    podAffinity: #设置pod亲和性
      requiredDuringSchedulingIgnoredDuringExecution: # 硬限制 同样还有软连接效果类似，只是即使未匹配依然可以运行
      - labelSelector:
          matchExpressions: # 匹配env的值在["aa","bb"]中的标签
          - key: podenv
            operator: In
            values: ["aa","bb"]
        topologyKey: kubernetes.io/hostname

# 启动pod
[root@k8s-master01 ~]# kubectl create -f pod-podaffinity-required.yaml
pod/pod-podaffinity-required created

# 查看pod状态，发现未运行
[root@k8s-master01 ~]# kubectl get pods pod-podaffinity-required -n dev
NAME                       READY   STATUS    RESTARTS   AGE
pod-podaffinity-required   0/1     Pending   0          9s

# 查看详细信息
[root@k8s-master01 ~]# kubectl describe pods pod-podaffinity-required  -n dev
......
Events:
  Type     Reason            Age        From               Message
  ----     ------            ----       ----               -------
  Warning  FailedScheduling  <unknown>  default-scheduler  0/3 nodes are available: 2 node(s) didn't match pod affinity rules, 1 node(s) had taints that the pod didn't tolerate.

# 接下来修改  values: ["aa","bb"]----->values:["pro","pod"]
[root@k8s-master01 ~]# vim pod-podaffinity-required.yaml

# 然后重新创建pod，查看效果
[root@k8s-master01 ~]# kubectl delete -f  pod-podaffinity-required.yaml
pod "pod-podaffinity-required" deleted
[root@k8s-master01 ~]# kubectl create -f pod-podaffinity-required.yaml
pod/pod-podaffinity-required created

# 发现此时Pod运行正常
[root@k8s-master01 ~]# kubectl get pods pod-podaffinity-required -n dev
NAME                       READY   STATUS    RESTARTS   AGE   LABELS
pod-podaffinity-required   1/1     Running   0          6s    <none>