kubernetes - kubectl应用-奇怪的空运行

Question

我面临着kubectl和--dry-run的怪异行为。

为简化起见，假设我具有以下yaml文件:

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  labels:
    run: nginx
  name: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      run: nginx
  strategy:
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
    type: RollingUpdate
  template:
    metadata:
      creationTimestamp: null
      labels:
        run: nginx
    spec:
      containers:
      - image: nginxsdf
        imagePullPolicy: Always
        name: nginx

修改例如图像或副本数:

kubectl apply -f Deployment.yaml -o yaml --dry-run向我输出具有 OLD 规范

的资源

kubectl apply -f Deployment.yaml -o yaml向我输出具有新规范

的资源

根据文档:

--dry-run=false: If true, only print the object that would be sent, without sending it.

但是，打印的对象是旧对象，而不是将被发送到ApiServer的对象。

在minikube，gke v1.10.0上测试

同时，我为此打开了一个新的gitHub问题:

https://github.com/kubernetes/kubernetes/issues/72644

Answer 1

我在kubernetes问题页面上得到了以下答案:

When updating existing objects, kubectl apply doesn't send an entire object, just a patch. It is not exactly correct to print either the existing object or the new object in dry-run mode... the outcome of the merge is what should be printed.

For kubectl to be able to accurately reflect the result of the apply, it would need to have the server-side apply logic clientside, which is a non-goal.

Current efforts are directed at moving apply logic to the server. As part of that, the ability to dry-run server-side has been added. kubectl apply --server-dry-run will do what you want, printing the result of the apply merge, without actually persisting it.

@apelisse we should probably update the flag help for apply and possibly print a warning when using --dry-run when updating an object via apply to document the limitations of --dry-run and direct people to use --server-dry-run