Rolling-Update-Deployment

Rolling Update Deployment Strategy

• A rolling update in Kubernetes is a deployment strategy used to gradually replace the existing set of Pods with a new set of Pods one by one.
• This ensures that there is no downtime during the update process as the application continues to serve requests while the update is in progress.

How it works ?

• Pod Creation: kubernetes creates one new pod of newer version.
• Pod Termination: It terminates existing pods.

Pro's	Con's
Version is slowly released across instances	Rollout/Rollback can take time
Convenient for stateful applications	No control over traffic

Note

This deployment strategy is suitable for UAT,QA environment. For stateful applications suitable on production environment

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Prerequisites to try this:

1. EC2 Instance with Ubuntu OS

2. Docker installed & Configured

3. Kind Installed

4. Kubectl Installed

5. Kind Cluster running(Use kind-config.yml file present in this directory.)

Note

You have to go inside root dir of this repo and create Kind Cluster using command: kind create cluster --config kind-config.yml --name dep-strg

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Steps to implement rolling-update deployment

• Apply all the manifest files present in the current directory.

  kubectl apply -f .

• Run this command to get all resources created in rolling-ns namespace.

  kubectl get all -n rolling-ns

• Forward the svc port to the EC2 instance port 3000

  kubectl port-forward --address 0.0.0.0 svc/rolling-update-service 3000:3000 -n rolling-ns &

• Open the inbound rule for port 3000 in that EC2 Instance and check the application at URL:

  http://<Your_Instance_Public_Ip>:3000

• Open a new tab of terminal and connect your EC2 instance and run the watch command to monitor the deployment

  watch kubectl get pods -n rolling-ns

• You have successfully accessed the online_shop with footer webpage. Now edit the deployment file and change the image from online_shop to online_shop_without_footer and apply.

  kubectl apply -f . 

• or, You can only apply deployment file

  kubectl apply -f rolling-deployment.yml

• Immediately go to second tab where ran watch command and monitor (It will delete all the pods and then create new ones).

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Cleanup

• Deleting Kind Cluster:

  kind delete cluster --name dep-strg

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Note

If you cannot access the web app after the update, check your terminal — you probably encountered an error like:

error: lost connection to pod

Don’t worry! This happens because we’re running the cluster locally (e.g., with Kind), and the kubectl port-forward session breaks when the underlying pod is replaced during deployment (especially with Recreate strategy).

🔁 Just run the kubectl port-forward command again to re-establish the connection and access the app in your browser.

✅ This issue won't occur when deploying on managed Kubernetes services like AWS EKS, GKE, or AKS, because in those environments you usually expose services using NodePort, LoadBalancer, or Ingress — not kubectl port-forward.