kubernetes ReplicaSet的簡單使用

建立ReplicaSet

ReplicaSet的配置以下

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: myapp
  namespace: default
spec:
  replicas: 2
  selector: 
    matchLabels:
      app: myapp
      release: canary
  template:
    metadata:
      name: myapp-pod
      labels: 
        app: myapp
        release: canary
        environment: qa
    spec:
      containers:
      - name: myapp-container
        image: ikubernetes/myapp:v1
        ports:
        - name: http
          containerPort: 80

在這個ReplicaSet中，咱們設置了兩個label，app=myapp, release=canary , 建立rs後，查看

[root@master manifests]# kubectl create -f rs-demo.yaml --dry-run
replicaset.apps/myapp created (dry run)
[root@master manifests]# kubectl create -f rs-demo.yaml 
replicaset.apps/myapp created
[root@master manifests]# kubectl get pods
NAME          READY     STATUS    RESTARTS   AGE
myapp-bj795   1/1       Running   0          18s
myapp-blmx8   1/1       Running   0          18s
[root@master manifests]# vim rs-demo.yaml 
[root@master manifests]# kubectl get pods --show-labels
NAME          READY     STATUS        RESTARTS   AGE       LABELS
myapp-b8sb5   1/1       Running       0          5m        app=myapp,environment=qa,release=canary
myapp-blmx8   1/1       Running       0          8m        app=myapp,environment=qa,release=canary
[root@master manifests]# kubectl get rs
NAME      DESIRED   CURRENT   READY     AGE
myapp     2         2         2         39s

實驗

ReplicaSet會經過label app=myapp, release=canary 來篩選Pod，而且設定的符合該label的Pod副本應該爲2個。

pod-demo.yaml文件的內容以下:

apiVersion: v1
kind: Pod
metadata:
  name: pod-demo
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    - name: https
      containerPort: 443
  - name: busybox
    image: busybox:latest
    #ImagePullPolicy: IfNotPresent
    command: 
    - "/bin/sh"
    - "-c"
    - "sleep 3600"

此時，咱們建立另外一個pod

[root@master manifests]# kubectl create -f pod-demo.yaml 
pod/pod-demo created
[root@master manifests]# kubectl get pods --show-labels
NAME          READY     STATUS    RESTARTS   AGE       LABELS
myapp-b8sb5   1/1       Running   0          5m        app=myapp,environment=qa,release=canary
myapp-blmx8   1/1       Running   0          7m        app=myapp,environment=qa,release=canary
pod-demo      2/2       Running   0          11s       app=myapp,tier=frontend

能夠看到，pod-demo的label爲 app=myapp,tier=frontend ，咱們嘗試給pod-demo添加一個label release=canary ，看下會出現什麼效果。

[root@master manifests]# kubectl label pods pod-demo release=canary
pod/pod-demo labeled
[root@master manifests]# kubectl get pods --show-labels
NAME          READY     STATUS        RESTARTS   AGE       LABELS
myapp-b8sb5   1/1       Running       0          5m        app=myapp,environment=qa,release=canary
myapp-blmx8   1/1       Running       0          8m        app=myapp,environment=qa,release=canary
pod-demo      2/2       Terminating   0          34s       app=myapp,release=canary,tier=frontend

能夠發現： pod-demo的狀態已經爲 Terminating。 說明ReplicaSet經過標籤選擇器獲取到了三個副本，而後預期的副本數被設定爲2，它隨機殺掉了一個。

應該是隨機的， 不過，我測試了幾回，都是把新建的pod-demo殺掉了。