k8s基本使用入门-了解ReplicaSet

现在，再去了解一个新的定义方式。
了解之前，先将刚刚的 pod 删除

[root@kube-node01 yaml]$ kubectl delete -f rc_nginx.yml
replicationcontroller "nginx" deleted

[root@kube-node01 yaml]$ kubectl get pods
NAME          READY     STATUS        RESTARTS   AGE
nginx-99nns   0/1       Terminating   0          6m
nginx-c5nk4   0/1       Terminating   0          49m
nginx-fjnrn   0/1       Terminating   0          6m
nginx-r2zcm   0/1       Terminating   0          49m

[root@kube-node01 yaml]$ kubectl get pods
NAME          READY     STATUS        RESTARTS   AGE
nginx-fjnrn   0/1       Terminating   0          6m

[root@kube-node01 yaml]$ kubectl get pods
No resources found.

可以看到 pod 会慢慢的消失掉，有点淡入淡出的那种感觉哈。

那么新的定义类型叫做ReplicaSet。

其实这个定义方式与上边介绍的ReplicationController非常像，官网这样介绍：

ReplicaSet 是下一代复制控制器。现在 ReplicaSet 和 Replication Controller 之间的唯一区别是选择器支持。ReplicaSet 支持标签用户指南中描述的新的基于集合的选择器要求， 而 Replication Controller 仅支持基于等同的选择器要求。

同样是定义一个 yaml 文件，如下：

[root@kube-node01 yaml]$ cat rs_nginx.yml
apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: nginx
  labels:
    tier: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      tier: frontend
  template:
    metadata:
      name: nginx
      labels:
        tier: frontend
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80

创建 pod:

[root@kube-node01 yaml]$ kubectl create -f rs_nginx.yml
replicaset.apps "nginx" created

[root@kube-node01 yaml]$ kubectl get pods
NAME          READY     STATUS              RESTARTS   AGE
nginx-4vp95   1/1       Running             0          8s
nginx-9xxp6   0/1       ContainerCreating   0          8s
nginx-f8vfg   1/1       Running             0          8s

[root@kube-node01 yaml]$ kubectl get rs
NAME      DESIRED   CURRENT   READY     AGE
nginx     3         3         1         4s

关于扩展等，与上边的一样

[root@kube-node01 yaml]$ kubectl scale rs nginx --replicas=2
replicaset.extensions "nginx" scaled

[root@kube-node01 yaml]$ kubectl get pods
NAME          READY     STATUS        RESTARTS   AGE
nginx-4vp95   1/1       Running       0          1m
nginx-9xxp6   0/1       Terminating   0          1m
nginx-f8vfg   1/1       Running       0          1m

[root@kube-node01 yaml]$ kubectl get rs
NAME      DESIRED   CURRENT   READY     AGE
nginx     2         2         2         1m
 
[root@kube-node01 yaml]$ kubectl scale rs nginx --replicas=5
replicaset.extensions "nginx" scaled

[root@kube-node01 yaml]$ kubectl get pods
NAME          READY     STATUS              RESTARTS   AGE
nginx-4vp95   1/1       Running             0          2m
nginx-bbxpk   0/1       ContainerCreating   0          2s
nginx-cg8ts   0/1       ContainerCreating   0          2s
nginx-f8vfg   1/1       Running             0          2m
nginx-sgvpd   0/1       ContainerCreating   0          2s

[root@kube-node01 yaml]$ kubectl get rs
NAME      DESIRED   CURRENT   READY     AGE
nginx     5         5         3         2m

[root@kube-node01 yaml]$ kubectl get rs
NAME      DESIRED   CURRENT   READY     AGE
nginx     5         5         4         2m

[root@master replicas-set]$kubectl get rs
NAME      DESIRED   CURRENT   READY     AGE
nginx     5         5         5         2m

这个知识点就到这里，可以根据以上的一些小实践，理解其工作方式