kubernetes not applying new service update from docker

Question

I have a node JS app which i am deploying to kubernetes.

I have made changes to node JS app and am redeploying the app to K8s.

However, I notice that the deployment is not making through.

I checked my docker hub and yes the latest image is being deployed. This is my service.yaml file below

apiVersion: v1
kind: Service
metadata:
  name: fourthapp
spec:
  type: LoadBalancer #Exposes the service as a node port
  ports:
  - port: 3000
    protocol: TCP
    targetPort: 3000
  selector:
    app: webapp

and this is my deploy.yaml file

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: fourthapp
spec:
  replicas: 2
  template:
    metadata:
      labels:
        app: webapp
    spec:
      containers:
      - name: webapp
        image: index.docker.io/leexha/nodejsapp:latest
        ports:
        - containerPort: 3000
        resources:
          requests: 
            memory: 500Mi
            cpu: 0.5
          limits:
            memory: 500Mi
            cpu: 0.5
        imagePullPolicy: Always

when i run the service.yaml it reads

C:\Users\adrlee\Desktop\oracle\Web_projects>kubectl apply -f service.yml
service "fourthapp" unchanged

Anything im doing wrong?

Do you want to either change the service or deploy the new docker image? — Giorgio Cerruti
– Giorgio Cerruti, Commented Sep 5, 2018 at 10:56
I managed to resolve it now. I made a slight adjustment in my yml file and it worked by adding in an image tag — Adam
– Adam, Commented Sep 5, 2018 at 15:43

Giorgio Cerruti · Accepted Answer · 2018-09-05 11:31:25Z

2

If I understood the question you should update the Deployment instead. The service is just a kind of LB which dispatch traffic between your pods.

First, you should add imagePullPolicy: Always to the deployment to force k8s to download the newest image.

If you want to update the deployment you can run

kubectl apply -f deploy.yml

or performing a Rolling Update

answered Sep 5, 2018 at 11:31

Giorgio Cerruti

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1 Comment

Adam Over a year ago

I did add an imagePullPolicy: always

David Maze · Accepted Answer · 2018-09-05 10:13:40Z

1

If you don't give every build of your image a distinct name, it's hard to force Kubernetes to restart a Deployment when the underlying image changes: it has no way of knowing that the "latest" tag on Docker Hub now means something else. (imagePullPolicy: Always will at least force it to get a new image if it happens to be restarting anyways.) When your run kubectl apply, it looks at the Deployment you're uploading, sees that it matches what's already running, and does nothing.

Best practice is to not use the "latest" tag and give some sort of unique identifier (timestamp, source control commit ID, ...). Then you can update the image ID in the pod spec, kubectl apply will see that something is different, and Kubernetes will perform a rolling update of the running pod(s) for you. This also has the advantage that, if a build is bad, you can easily go backwards by changing the image tag back to a previous build.

answered Sep 5, 2018 at 10:13

David Maze

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4 Comments

Adam Over a year ago

so i tried to tag a unique tag like 0d4992bcf07932cecedfb462fcace2ef9620d916 to the image . However, it still gives me a service "fourthapp" unchanged

David Maze Over a year ago

And you changed the deployment spec to say image: leexha/nodejsapp:0d4992bcf...916?

Adam Over a year ago

yes i did. apiVersion: extensions/v1beta1 kind: Deployment metadata: name: fourthapp spec: replicas: 2 template: metadata: labels: app: webapp spec: containers: - name: webapp image: index.docker.io/leexha/nodejsapp:0d4992bcf07932cecedfb462fcace2ef9620d916 ports: - containerPort: 3000 resources: requests: memory: 500Mi cpu: 0.5 limits: memory: 500Mi cpu: 0.5 imagePullPolicy: Always

David Maze Over a year ago

As @GiorgioCerruti says in his answer, you need to re-apply the deployment. The service will always be unchanged.

Lauri · Accepted Answer · 2018-09-05 10:30:37Z

1

Kubernetes won't update running pods unless the pod spec is changed. If you want force the deployment you can run after the apply command:

kubectl patch deployment fourthapp -p "{\"spec\":{\"template\":{\"metadata\":{\"annotations\":{\"date\":\"`date +'%s'`\"}}}}}"

It will add/update special date annotation on the pod template and Kubernetes will update running pods.

answered Sep 5, 2018 at 10:30

Lauri

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