1，RS介绍

ReplicaSet是下一代复本控制器。RS和RC之间的唯一区别是现在的选择器支持。RC只支持基于等式的selector（env=dev或environment!=qa），但RS还支持新的，基于集合的selector（version in (v1.0, v2.0)或env notin (dev, qa)）。
在新版本的 Kubernetes 中建议使用RS来取代RC，虽然也RS可以独立使用，但建议使用 Deployment 来自动管理 RS，这样就无需担心跟其他机制的不兼容问题（比如 RS 不支持 rolling-update 但 Deployment 支持），并且Deployment还支持版本记录、回滚、暂停升级等高级特性

2，示例

  1. apiVersion: extensions/v1beta1
  2. kind: ReplicaSet
  3. metadata:
  4.   name: frontend
  5.   # these labels can be applied automatically
  6.   # from the labels in the pod template if not set
  7.   # labels:
  8.     # app: guestbook
  9.     # tier: frontend
  10. spec:
  11.   # this replicas value is default
  12.   # modify it according to your case
  13.   replicas: 3
  14.   # selector can be applied automatically
  15.   # from the labels in the pod template if not set,
  16.   # but we are specifying the selector here to
  17.   # demonstrate its usage.
  18.   selector:
  19.     matchLabels:
  20.       tier: frontend
  21.     matchExpressions:
  22.       - {key: tier, operator: In, values: [frontend]}
  23.   template:
  24.     metadata:
  25.       labels:
  26.         app: guestbook
  27.         tier: frontend
  28.     spec:
  29.       containers:
  30.       - name: php-redis
  31.         image: gcr.io/google_samples/gb-frontend:v3
  32.         resources:
  33.           requests:
  34.             cpu: 100m
  35.             memory: 100Mi
  36.         env:
  37.         - name: GET_HOSTS_FROM
  38.           value: dns
  39.           # If your cluster config does not include a dns service, then to
  40.           # instead access environment variables to find service host
  41.           # info, comment out the 'value: dns' line above, and uncomment the
  42.           # line below.
  43.           # value: env
  44.         ports:
  45.         - containerPort: 80
  1. # 通过create创建好后可以查看pod信息
  2. $ kubectl describe rs/frontend
  3. Name:          frontend
  4. Namespace:     default
  5. Image(s):      gcr.io/google_samples/gb-frontend:v3
  6. Selector:      tier=frontend,tier in (frontend)
  7. Labels:        app=guestbook,tier=frontend
  8. Replicas:      3 current / 3 desired
  9. Pods Status:   3 Running / 0 Waiting / 0 Succeeded / 0 Failed
  10. No volumes.
  11. Events:
  12.   FirstSeen    LastSeen    Count    From                SubobjectPath    Type        Reason            Message
  13.   ---------    --------    -----    ----                -------------    --------    ------            -------
  14.   1m           1m          1        {replicaset-controller }             Normal      SuccessfulCreate  Created pod: frontend-qhloh
  15.   1m           1m          1        {replicaset-controller }             Normal      SuccessfulCreate  Created pod: frontend-dnjpy
  16.   1m           1m          1        {replicaset-controller }             Normal      SuccessfulCreate  Created pod: frontend-9si5l
  18. $ kubectl get pods
  19. NAME             READY     STATUS    RESTARTS   AGE
  20. frontend-9si5l   1/1       Running   0          1m
  21. frontend-dnjpy   1/1       Running   0          1m
  22. frontend-qhloh   1/1       Running   0          1m