5、kubernetes Scale Up/Down在线增加或减少 Pod 的副本数、Failover故障转移、用 label(标签)控制 Pod 的位置

伸缩（Scale Up/Down）是指在线增加或减少 Pod 的副本数。

Deployment nginx-app 初始是两个副本

[root@master ~]# kubectl  apply  -f nginx.yaml 
deployment.apps/nginx-app created
[root@master ~]# kubectl get pod -o wide
NAME                         READY   STATUS    RESTARTS   AGE   IP           NODE    NOMINATED NODE   READINESS GATES
nginx-app-7f4fc68488-4szxm   1/1     Running   0          91s   10.244.2.5   node2   <none>           <none>
nginx-app-7f4fc68488-zxbg8   1/1     Running   0          91s   10.244.1.4   node1   <none>           <none>

node1 和 knode2 上各跑了一个副本。现在修改 nginx.yml，将副本改成 5 个

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-app
spec:
  selector:
    matchLabels:
      app: nginx
  # 部署的实例数量改为5
  replicas: 5
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.17
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 80

 再次执行 kubectl apply：

[root@master ~]# kubectl  apply  -f nginx.yaml 
deployment.apps/nginx-app configured
[root@master ~]# kubectl get pod -o wide
NAME                         READY   STATUS    RESTARTS   AGE     IP           NODE    NOMINATED NODE   READINESS GATES
nginx-app-7f4fc68488-4szxm   1/1     Running   0          4m19s   10.244.2.5   node2   <none>           <none>
nginx-app-7f4fc68488-9zwlc   1/1     Running   0          94s     10.244.2.7   node2   <none>           <none>
nginx-app-7f4fc68488-cmdfj   1/1     Running   0          94s     10.244.1.5   node1   <none>           <none>
nginx-app-7f4fc68488-tw9nn   1/1     Running   0          94s     10.244.2.6   node2   <none>           <none>
nginx-app-7f4fc68488-zxbg8   1/1     Running   0          4m19s   10.244.1.4   node1   <none>           <none>
[root@master ~]# 

三个新副本被创建并调度到 k8s-node1 和 k8s-node2 上。
出于安全考虑，默认配置下 Kubernetes 不会将 Pod 调度到 Master 节点。如果希望将 k8s-master 也当作 Node 使用，可以执行如下命令：

kubectl taint node k8s-master node-role.kubernetes.io/master-

如果要恢复