Kubernetes報錯:MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable

報錯信息

MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable

原因

原因：這個問題的本質原因是，兩個相同的Deployment（一個已部署，一個要部署），但它們選擇器不同。

場景復現

例：
app.yaml

apiVersion: apps/v1                                                                  kind: Deployment
metadata:
  name: my-app
  labels:
    app: my-app
spec:
  replicas: 10
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
        version: v1.0.0
      annotations:
        prometheus.io/scrape: "true"
        prometheus.io/port: "9101"
    spec:
      containers:
      - name: my-app
        image: containersol/k8s-deployment-strategies
        ports:
        - name: http
          containerPort: 8080
        - name: probe
          containerPort: 8086
        env:
        - name: VERSION
          value: v1.0.0
        livenessProbe:
          httpGet:
            path: /live
            port: probe
          initialDelaySeconds: 5
          periodSeconds: 5
        readinessProbe:
          httpGet:
            path: /ready
            port: probe
          periodSeconds: 5

部署完成之後，查看一下結果

$kubectl get deployment
NAME     READY   UP-TO-DATE   AVAILABLE   AGE
my-app   10/10   10           10          84s

接下來，我們修改deployment的選擇器，主要內容如下

spec:
  replicas: 10
  selector:
    matchLabels:
      app: my-app-change
  template:
    metadata:
      labels:
        app: my-app-change
        version: v1.0.0

完成文件如下:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
  labels:
    app: my-app
spec:
  replicas: 10
  selector:
    matchLabels:
      app: my-app-change
  template:
    metadata:
      labels:
        app: my-app-change
        version: v1.0.0
      annotations:
        prometheus.io/scrape: "true"
        prometheus.io/port: "9101"
    spec:
      containers:
      - name: my-app
        image: containersol/k8s-deployment-strategies
        ports:
        - name: http
          containerPort: 8080
        - name: probe
          containerPort: 8086
        env:
        - name: VERSION
          value: v1.0.0
        livenessProbe:
          httpGet:
            path: /live
            port: probe
          initialDelaySeconds: 5
          periodSeconds: 5
        readinessProbe:
          httpGet:
            path: /ready
            port: probe
          periodSeconds: 5

部署的時候，會出現如下報錯：

$kubectl apply -f app.yaml
The Deployment "my-app" is invalid: spec.selector: Invalid value: v1.LabelSelector{MatchLabels:map[string]string{"app":"my-app-change"}, MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable

可以看已經部署的deployment的selector：

$kubectl describe deployment my-app
Name:                   my-app
...
Selector:               app=my-app
...

可以看到deployment名字爲my-app的已經有了選擇器，內容爲app=my-app。而此時，報錯的原因是因爲新部署的deployment名字也爲my-app，但是選擇器的內容是app=my-app-change。

解決方式：

1： 可以將原先的deployment刪除後再部署
2： 修改deployment的名字，不要重名