Challenge, Easy,  on  Kubernetes

Switch Live Traffic from Blue to Green Using Kubernetes Services

Omkar Shelke
by  Omkar Shelke

Scenario

You are running a live web application web-app-blue in the ios namespace, served by a Service named web-app-service exposed on NodePort 32222. A new version of the application is ready to go live.

Rather than performing a rolling update, the team is using a blue-green deployment strategy — running both versions simultaneously and switching traffic instantly by updating the Service selector.

The web-app-service currently routes all traffic to the blue deployment. Your job is to deploy the green version and cut over traffic with zero downtime.

Task

1. Create a Deployment named web-app-green in the ios namespace using the same structure as the Blue deployment:

  • Image: public.ecr.aws/docker/library/nginx:stable-perl
  • Replicas: 3
  • Labels: app: web-app, color: green
  • Mount the existing ConfigMap web-app-green-config at /usr/share/nginx/html/index.html using subPath

2. Do not route traffic to it yet — wait until all 3 green pods are Running.

3. Switch the Service selector on web-app-service from color: blue to color: green — traffic will instantly shift to the green deployment.

Kubernetes blue green deployment service selector routing switch diagram

Blue-Green Switching: Updating the Service selector from Blue to Green instantly reroutes traffic with zero downtime.

After switching, confirm the green page is served on NodePort 32222:

curl cplane-01:32222
Hint 1

Use the same structure as the blue deployment but with the green image, green labels, and the web-app-green-config ConfigMap:

kubectl get deployment web-app-blue -n ios -o yaml

Once green pods are running, patch the Service selector to point to green.

Use this as a reference to create the green deployment with the updated image and labels:

Test Cases

How to Author Challenges on iximiuz Labs

Instead of providing a subpar online editing experience, iximiuz Labs offers a helper CLI tool called labctl, allowing you to use your favorite text editor (or a full-featured IDE) to write content from the comfort of your local machine.

Install labctl CLI

curl -sf https://labs.iximiuz.com/cli/install.sh | sh

This will download and install the latest version of the labctl CLI. You only need to do this once per workstation.

Authorize labctl

labctl auth login

This will open a browser window asking you to authorize labctl to access your account. You need to do it after a fresh install of labctl and repeat it whenever the auth session expires.

Pull challenge content

labctl content pull challenge switch-live-traffic-from-blue-to-green-using-kubernetes-services-6d85e0c2

This will create a local copy of the challenge content in a directory named switch-live-traffic-from-blue-to-green-using-kubernetes-services-6d85e0c2. You only need to do this once per challenge.

Stream your changes

labctl content push -fw challenge switch-live-traffic-from-blue-to-green-using-kubernetes-services-6d85e0c2

Run this command in a separate terminal to continuously upload your changes to the server while editing the challenge in your favorite text editor or IDE.

You can also use labctl to create, list, and delete your content. Learn more about the available commands: labctl content --help

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