一般情况下pod的数量不会是一个，多个pod可以让服务更加的可靠并且可以承受更大的流量。

service的type类型可以为LoadBalancer即负载均衡。使用该类型service需要指定外部负载均衡器的ip以及nodeport和clusterip

查看deployment和ReplicaSet，ReplicaSet的命名格式为【deployment】-【随机字符串】

$ kubectl get deployments
NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   1/1     1            1           3m21s
$ kubectl get rs
NAME                            DESIRED   CURRENT   READY   AGE
kubernetes-bootcamp-fb5c67579   1         1         1       4m6s

ReplicaSet的desired为启动程序所需的副本数量，current为当前运行的副本数量

使用kubectl scale命令扩容

$ kubectl scale deployments/kubernetes-bootcamp --replicas=4
deployment.apps/kubernetes-bootcamp scaled
$ kubectl get rs
NAME                            DESIRED   CURRENT   READY   AGE
kubernetes-bootcamp-fb5c67579   4         4         4       8m33s
$ kubectl get deployments
NAME                  READY   UP-TO-DATE   AVAILABLE   AGE
kubernetes-bootcamp   4/4     4            4           9m22s

此时副本已经被扩容到了4个，对应的pod数量也随之增长

$ kubectl get pods -o wide
NAME                                  READY   STATUS    RESTARTS   AGE     IP           NODE       NOMINATED NODE   READINESS GATES
kubernetes-bootcamp-fb5c67579-kwng8   1/1     Running   0          3m20s   172.18.0.8   minikube   <none>           <none>
kubernetes-bootcamp-fb5c67579-vxrl5   1/1     Running   0          9m45s   172.18.0.4   minikube   <none>           <none>
kubernetes-bootcamp-fb5c67579-w7w4s   1/1     Running   0          3m20s   172.18.0.9   minikube   <none>           <none>
kubernetes-bootcamp-fb5c67579-zfl6g   1/1     Running   0          3m20s   172.18.0.7   minikube   <none>           <none>

这些deployment的变化被记录在deployment时事件日志中

$ kubectl describe deployments/kubernetes-bootcamp
Name:                   kubernetes-bootcamp
Namespace:              default
CreationTimestamp:      Wed, 10 Nov 2021 15:52:21 +0000
Labels:                 app=kubernetes-bootcamp
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               app=kubernetes-bootcamp
Replicas:               4 desired | 4 updated | 4 total | 4 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=kubernetes-bootcamp
  Containers:
   kubernetes-bootcamp:
    Image:        gcr.io/google-samples/kubernetes-bootcamp:v1
    Port:         8080/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Progressing    True    NewReplicaSetAvailable
  Available      True    MinimumReplicasAvailable
OldReplicaSets:  <none>
NewReplicaSet:   kubernetes-bootcamp-fb5c67579 (4/4 replicas created)
Events:
  Type    Reason             Age    From                   Message
  ----    ------             ----   ----                   -------
  Normal  ScalingReplicaSet  11m    deployment-controller  Scaled up replica set kubernetes-bootcamp-fb5c67579 to 1
  Normal  ScalingReplicaSet  4m52s  deployment-controller  Scaled up replica set kubernetes-bootcamp-fb5c67579 to 4

events显示了刚才操作的扩容事件

service负载均衡会把请求分流到不同的pod上

$ curl $(minikube ip):$NODE_PORT
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-fb5c67579-zfl6g | v=1
$ curl $(minikube ip):$NODE_PORT
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-fb5c67579-w7w4s | v=1
$ curl $(minikube ip):$NODE_PORT
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-fb5c67579-vxrl5 | v=1
$ curl $(minikube ip):$NODE_PORT
Hello Kubernetes bootcamp! | Running on: kubernetes-bootcamp-fb5c67579-kwng8 | v=1

同样的，可以使用scale缩容，但是副本数量没有变化，只是根据所需的副本数量停掉其他的pod

$ kubectl get pods -o wide
NAME                                  READY   STATUS        RESTARTS   AGE   IP           NODE       NOMINATED NODE   READINESS GATES
kubernetes-bootcamp-fb5c67579-kwng8   1/1     Terminating   0          10m   172.18.0.8   minikube   <none>           <none>
kubernetes-bootcamp-fb5c67579-vxrl5   1/1     Running       0          17m   172.18.0.4   minikube   <none>           <none>
kubernetes-bootcamp-fb5c67579-w7w4s   1/1     Terminating   0          10m   172.18.0.9   minikube   <none>           <none>
kubernetes-bootcamp-fb5c67579-zfl6g   1/1     Running       0          10m   172.18.0.7   minikube   <none>