Google cloud Kubernetes deployment error: Field is immutable

Question

After fixing the problem from this topic Can't use Google Cloud Kubernetes substitutions (yaml files are all there, to not copy-paste them once again) I got a new problem. Making a new topic because there is the correct answer for the previous one.

Step #2: Running: kubectl apply -f deployment.yaml
Step #2: Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply
Step #2: The Deployment "myproject" is invalid: spec.selector: Invalid value: v1.LabelSelector{MatchLabels:map[string]string{"app":"myproject", "run":"myproject"}, MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable

I've checked similar issues but hasn't been able to find anything related.

Also, is that possible that this error related to upgrading App Engine -> Docker -> Kubernetes? I created valid configuration on each step. Maybe there are some things that were created and immutable now? What should I do in this case?

One more note, maybe that matters, it says "kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply" (you can see above), but executing

kubectl create deployment myproject --image=gcr.io/myproject/myproject

gives me this

Error from server (AlreadyExists): deployments.apps "myproject" already exists

which is actually expected, but, at the same time, controversial with warning above (at least from my prospective)

Any idea?

Output of kubectl version

Client Version: version.Info{Major:"1", Minor:"14", GitVersion:"v1.14.7", GitCommit:"8fca2ec50a6133511b771a11559e24191b1aa2b4", GitTreeState:"clean", BuildDate:"2019-09-18T14:47:22Z", GoVersion:"go1.12.9", Compiler:"gc", Platform:"darwin/amd64"}
Server Version: version.Info{Major:"1", Minor:"13+", GitVersion:"v1.13.11-gke.14", GitCommit:"56d89863d1033f9668ddd6e1c1aea81cd846ef88", GitTreeState:"clean", BuildDate:"2019-11-07T19:12:22Z", GoVersion:"go1.12.11b4", Compiler:"gc", Platform:"linux/amd64"}

Current YAML file:

steps:
  - name: 'gcr.io/cloud-builders/docker'
    entrypoint: 'bash'
    args: [
      '-c',
      'docker pull gcr.io/$PROJECT_ID/myproject:latest || exit 0'
    ]
  - name: 'gcr.io/cloud-builders/docker'
    args: [
      'build',
      '-t',
      'gcr.io/$PROJECT_ID/myproject:$BRANCH_NAME-$COMMIT_SHA',
      '-t',
      'gcr.io/$PROJECT_ID/myproject:latest',
      '.'
    ]
  - name: 'gcr.io/cloud-builders/kubectl'
    args: [ 'apply', '-f', 'deployment.yaml' ]
    env:
      - 'CLOUDSDK_COMPUTE_ZONE=<region>'
      - 'CLOUDSDK_CONTAINER_CLUSTER=myproject'
  - name: 'gcr.io/cloud-builders/kubectl'
    args: [
      'set',
      'image',
      'deployment',
      'myproject',
      'myproject=gcr.io/$PROJECT_ID/myproject:$BRANCH_NAME-$COMMIT_SHA'
    ]
    env:
      - 'CLOUDSDK_COMPUTE_ZONE=<region>'
      - 'CLOUDSDK_CONTAINER_CLUSTER=myproject'
      - 'DB_PORT=5432'
      - 'DB_SCHEMA=public'
      - 'TYPEORM_CONNECTION=postgres'
      - 'FE=myproject'
      - 'V=1'
      - 'CLEAR_DB=true'
      - 'BUCKET_NAME=myproject'
      - 'BUCKET_TYPE=google'
      - 'KMS_KEY_NAME=storagekey'
timeout: 1600s
images:
  - 'gcr.io/$PROJECT_ID/myproject:$BRANCH_NAME-$COMMIT_SHA'
  - 'gcr.io/$PROJECT_ID/myproject:latest

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myproject
spec:
  replicas: 1
  selector:
    matchLabels:
      app: myproject
  template:
    metadata:
      labels:
        app: myproject
    spec:
      containers:
        - name: myproject
          image: gcr.io/myproject/github.com/weekendman/{{repo name here}}:latest
          ports:
            - containerPort: 80

Answer 1

From apps/v1 on, a Deployment’s label selector is immutable after it gets created.

excerpt from Kubernetes's document:

Note: In API version apps/v1, a Deployment’s label selector is immutable after it gets created.

So, you can delete this deployment first, then apply it.

Answer 2

The MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable because it is different from your previous deployment.

Try looking at the existing deployment with kubectl get deployment -o yaml. I suspect the existing yaml has a different matchLables stanza.

Specifically your file has:

    matchLabels:
      app: myproject

my guess is the output of kubectl get deployment -o yaml while have something different, like:

    matchLabels:
      app: old-project-name

or

    matchLabels:
      app: myproject
      version: alpha

The new deployment cannot change the matchLabels stanza because, well, because it is immutable. That stanza in the new deployment must match the old. If you want to change it, you need to delete the old deployment with kubectl delete deployment myproject.

Note: if you do that in production your app will be unavailable for a while. (A much longer discussion about how to do this in production is not useful here.)