deployment标签（labels）匹配相关知识：spec.selector.matchLables与spec.template.metadata.lables

Posted 2022-09-03 Locutus

1. spec.selector.matchLables实验

1.1 正确的Deployment书写方式，是要让spec.selector.matchLabels值和spec.template.metadata.lables值完全匹配，这样才不会报错。

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-nginx
spec:
  selector:
    matchLabels:
      app: my-nginx
  replicas: 2
  template:
    metadata:
      labels:
        app: my-nginx
    spec:
      containers:
      - name: my-nginx
        image: nginx
        ports:
        - containerPort: 80

创建pod成功

# kubectl get pods

NAME                      READY   STATUS    RESTARTS   AGE
my-nginx-9b44d8f5-d6n8z   1/1     Running   0          3s
my-nginx-9b44d8f5-zzv52   1/1     Running   0          3s

1.2 如果不写spec.selector.matchLabels字段的内容，直接创建则会报错：缺少必要字段selector

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-nginx
spec:
  replicas: 2
  template:
    metadata:
      labels:
        app: my-nginx
    spec:
      containers:
      - name: my-nginx
        image: nginx
        ports:
        - containerPort: 80

# kubectl create -f test_pod_svc.yaml

error: error validating "test_pod_svc.yaml": error validating data: ValidationError(Deployment.spec): missing required field "selector" in io.k8s.api.apps.v1.DeploymentSpec; if you choose to ignore these errors, turn validation off with --validate=false

1.3 当spec.selector.matchLabels匹配的键值，与spec.template.metadata.lables键值不相对应，也会直接报错：选择的和模板标签不匹配

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-nginx
spec:
  selector:
    matchLabels:
      app: my-nginx-add
  replicas: 2
  template:
    metadata:
      labels:
        app: my-nginx
    spec:
      containers:
      - name: my-nginx
        image: nginx:1.14
        ports:
        - containerPort: 80

# kubectl create -f test_pod_svc.yaml

The Deployment "my-nginx" is invalid: spec.template.metadata.labels: Invalid value: map[string]string"app":"my-nginx": `selector` does not match template `labels`

1.4 查看帮助手册

# kubectl explain Deployment.spec 

selector  <Object>
Label selector for pods. Existing ReplicaSets whose pods are selected by this will be the ones affected by this deployment.

pod的标签选择器。 由此选择其pod的现有ReplicaSet(副本集)将受此部署影响的副本。

2. 总结

• 在deployment.yaml中必须写spec.selector.matchLabels

• 在定义pod模板时，必须定义spec.template.metadata.lables，因为spec.selector.matchLabels是必须字段，而它又必须和spec.template.metadata.lables的键值一致。

• spec.template.metadata.lables里面定义的内容，会应用到spec.template.spec下定义的所有pod副本中，在spec.template.spec.containers里面不能定义labels标签

3. 参考文章

https://cloud.tencent.com/developer/article/1394657