03-rolling-updates.md

Replicas and Rolling update

Create Deployment

💡 All files for the exercise are found in the rolling-updates folder.

• Look at the nginx deployment yaml file in rolling-updates/nginx-deployment.yaml
• Look at the service file in rolling-updates/nginx-svc.yaml

Now go ahead and apply the deployment and the service:

• Apply the nginx deployment: $ kubectl apply -f rolling-updates/nginx-deployment.yaml
• Apply the service: $ kubectl apply -f rolling-updates/nginx-svc.yaml

💡 Remember that it might take a few minutes for the cloud infrastructure to deploy the load balancer, i.e. the external IP might be shown as pending

• Note down the loadbalancer IP from the services command: $ kubectl get service
• Increase the replicas to four in the deployment yaml file:

spec:
  replicas: 4

• Apply the service again to increase the replica count of your deployment.

From another terminal check which version is currently running and to see changes when rollout is happening:

$ while true; do  curl --connect-timeout 1 -m 1 -sI <loadbalancerIP>  | grep Server; sleep 0.5; done

Update Deployment

Now we will try to roll out an update to the image.

• Set image tag to 1.9:

    ...
    spec:
      containers:
      - image: nginx:1.9

• Apply the new version of your deployment.

• Check the rollout status: $ kubectl rollout status deployment nginx

• Investigate rollout history: $ kubectl rollout history deployment nginx

• Try rolling out other image version by repeating the commands from above. Suggested image versions are 1.12.2, 1.13.12, 1.14.1, 1.15.2.

• Try also rolling out a version that does not exist:

    spec:
      containers:
      - image: nginx:not-a-version
        name: nginx

What happened - do the curl operation still work?

• Investigate the running pods with: $ kubectl get pods

Undo Update

The rollout above using a non-existing image version caused some pods to be non-functioning. Next, we will undo this faulty deployment.

• Investigate rollout history: kubectl rollout history deployment nginx

• Undo the rollout and restore the previous version: kubectl rollout undo deployment nginx

• Investigate the running pods: kubectl get pods

Clean up

Delete deployments and services as follow:

• kubectl delete deployment nginx
• kubectl delete service nginx