ReplicaSet控制器

ReplicationController用来确保容器应用的副本数始终保持在用户定义的副本数，即如果有容器异常退出，会自动创建新的Pod来替代；而如果异常多出来的容器也会自动回收,属于旧版本的控制器,涉及面太复杂.

在新版本的Kubernetes中建议使用ReplicaSet来取代ReplicationController。ReplicaSet跟ReplicationController没有本质的不同，只是名字不一样，并且ReplicaSet支持集合式的selector。

虽然ReplicaSet可以独立使用，但一般还是建议使用 Deployment 来自动管理ReplicaSet，这样就无需担心跟其他机制的不兼容问题（比如ReplicaSet不支持rolling-update但Deployment支持），而且Deployment支持滚动升级及回滚

命令行查看ReplicaSet清单定义规则

kubectl explain replicaSet
kubectl explain replicaSet.spec

ReplicaSet资源清单

[root@k8s-master01 learning]# vim replicaSet-demo.yaml 
apiVersion: apps/v1 #api版本定义
kind: ReplicaSet    #定义资源类型为ReplicaSet
metadata:           #元数据定义
  name: rs-demo
  namespace: learning
spec:               #ReplicaSet的规格定义
  replicas: 2       #定义副本数量为2个
  selector:         #标签选择器，定义匹配pod的标签
    matchLabels:
      app: rs-demo
      tag: learn-rs
  template:         #pod的模板定义
    metadata:       #pod的元数据定义
      name: rs-demo #自定义pod的名称　
      labels:       #定义pod的标签，和上面保持一致或多余上面
        app: rs-demo
        tag: learn-rs
    spec:           #pod的规格定义  
      containers:   #容器定义
        - name: rs-demo       #容器名称
          image: nginx:1.10   #容器镜像
          ports:              #暴露端口
            - name: http
              containerPort: 80

[root@k8s-master01 learning]# kubectl create namespace learning
namespace/learning created

[root@k8s-master01 learning]# kubectl apply -f replicaSet-demo.yaml  
replicaset.apps/rs-demo created

ReplicaSet常用命令

查看资源

# 查看现有rs
[root@k8s-master01 learning]# kubectl get replicasets.apps  -n learning 
NAME      DESIRED   CURRENT   READY   AGE
rs-demo   2         2         2       4m44s

# 查看详细信息
[root@k8s-master01 learning]# kubectl describe replicasets. -n learning  rs-demo 
Name:         rs-demo
Namespace:    learning
Selector:     app=rs-demo,tag=learn-rs
Labels:       <none>
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"apps/v1","kind":"ReplicaSet","metadata":{"annotations":{},"name":"rs-demo","namespace":"learning"},"spec":{"replicas":5,"se...
Replicas:     5 current / 5 desired
Pods Status:  5 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
  Labels:  app=rs-demo
           tag=learn-rs
  Containers:
   rs-demo:
    Image:        nginx:1.11
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Events:
  Type    Reason            Age   From                   Message
  ----    ------            ----  ----                   -------
  Normal  SuccessfulCreate  22s   replicaset-controller  Created pod: rs-demo-5pd54
  Normal  SuccessfulCreate  22s   replicaset-controller  Created pod: rs-demo-gndz6
  Normal  SuccessfulCreate  22s   replicaset-controller  Created pod: rs-demo-p479c
  Normal  SuccessfulCreate  22s   replicaset-controller  Created pod: rs-demo-bkc28
  Normal  SuccessfulCreate  22s   replicaset-controller  Created pod: rs-demo-x57kj

修改Pod数量

# 修改pod的副本数量
# (1) 通过配置文件修改
[root@k8s-master01 learning]# sed -i 's/  replicas: 2/  replicas: 5/g' replicaSet-demo.yaml 
[root@k8s-master01 learning]# kubectl apply -f replicaSet-demo.yaml 
replicaset.apps/rs-demo configured
[root@k8s-master01 learning]# kubectl get rs -n learning 
NAME      DESIRED   CURRENT   READY   AGE
rs-demo   5         5         5       7m37s
[root@k8s-master01 learning]# kubectl get pods -n learning 
NAME            READY   STATUS    RESTARTS   AGE
rs-demo-h29s7   1/1     Running   0          10s
rs-demo-k778n   1/1     Running   0          7m5s
rs-demo-mmvpz   1/1     Running   0          10s
rs-demo-pw9l8   1/1     Running   0          10s
rs-demo-s7q75   1/1     Running   0          7m5s

# (2) edit直接编辑修改
[root@k8s-master01 learning]# kubectl edit -n learning replicasets.apps rs-demo
直接修改replicas字段为想要的pod个数, wq保存退出
[root@k8s-master01 learning]# kubectl -n learning  get replicasets.
NAME      DESIRED   CURRENT   READY   AGE
rs-demo   3         3         3       12m

修改镜像版本

# 查看现有的
[root@k8s-master01 learning]# kubectl -n learning  get replicasets. -o wide
NAME      DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES       SELECTOR
rs-demo   3         3         3       13m   rs-demo      nginx:1.10   app=rs-demo,tag=learn-rs

# (1) 通过配置文件修改
[root@k8s-master01 learning]# sed -i 's/          image: nginx:1.10/          image: nginx:1.11/g' replicaSet-demo.yaml
[root@k8s-master01 learning]# kubectl apply -f replicaSet-demo.yaml 
replicaset.apps/rs-demo configured
[root@k8s-master01 learning]# kubectl -n learning  get replicasets. -o wide
NAME      DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES       SELECTOR
rs-demo   5         5         5       29m   rs-demo      nginx:1.11   app=rs-demo,tag=learn-rs

# (2) edit直接编辑修改
[root@k8s-master01 learning]# kubectl edit -n learning replicasets.apps rs-demo
直接修改image字段为想要的pod个数, wq保存退出
[root@k8s-master01 learning]# kubectl -n learning  get replicasets. -o wide
NAME      DESIRED   CURRENT   READY   AGE   CONTAINERS   IMAGES       SELECTOR
rs-demo   5         5         5       38m   rs-demo      nginx:1.12   app=rs-demo,tag=learn-rs