Blue-green deployments in Kubernetes - Mini Project: Build & Apply

Blue-green deployments

📖 Scenario: You are managing a web application running on Kubernetes. You want to deploy a new version of your app without downtime by using blue-green deployment strategy.

🎯 Goal: Build a simple blue-green deployment setup in Kubernetes using two deployments and a service that switches traffic between them.

📋 What You'll Learn

Create two deployments named blue-deployment and green-deployment with different app versions

Create a service named app-service that routes traffic to the active deployment

Switch the service selector from blue to green to simulate deployment switch

💡 Why This Matters

🌍 Real World

Blue-green deployments are used in production environments to update applications without downtime by running two identical environments and switching traffic.

💼 Career

Understanding blue-green deployments is essential for DevOps engineers and site reliability engineers to manage safe application rollouts.

1

Create the blue deployment

Create a Kubernetes deployment named blue-deployment with label app: blue and container image nginx:1.19.

Kubernetes

# Your code here

Need a hint?

Use kind: Deployment and set metadata.name to blue-deployment. Use label app: blue in spec.template.metadata.labels. Use container image nginx:1.19.

2

Create the green deployment

Create a Kubernetes deployment named green-deployment with label app: green and container image nginx:1.20.

Kubernetes

apiVersion: apps/v1
kind: Deployment
metadata:
  name: blue-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: blue
  template:
    metadata:
      labels:
        app: blue
    spec:
      containers:
      - name: nginx
        image: nginx:1.19
        ports:
        - containerPort: 80

# Your code here

Need a hint?

Similar to blue deployment, but name it green-deployment, label app: green, and use image nginx:1.20.

3

Create the service routing to blue deployment

Create a Kubernetes service named app-service that routes traffic to pods with label app: blue on port 80.

Kubernetes

apiVersion: apps/v1
kind: Deployment
metadata:
  name: blue-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: blue
  template:
    metadata:
      labels:
        app: blue
    spec:
      containers:
      - name: nginx
        image: nginx:1.19
        ports:
        - containerPort: 80
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: green-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: green
  template:
    metadata:
      labels:
        app: green
    spec:
      containers:
      - name: nginx
        image: nginx:1.20
        ports:
        - containerPort: 80

# Your code here

Need a hint?

Create a Service with metadata.name as app-service. Set spec.selector.app to blue and expose port 80.

4

Switch service to green deployment

Change the app-service selector from app: blue to app: green to route traffic to the green deployment. Then print the selector line to confirm.

Kubernetes

apiVersion: apps/v1
kind: Deployment
metadata:
  name: blue-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: blue
  template:
    metadata:
      labels:
        app: blue
    spec:
      containers:
      - name: nginx
        image: nginx:1.19
        ports:
        - containerPort: 80
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: green-deployment
spec:
  replicas: 2
  selector:
    matchLabels:
      app: green
  template:
    metadata:
      labels:
        app: green
    spec:
      containers:
      - name: nginx
        image: nginx:1.20
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: app-service
spec:
  selector:
    app: blue
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

# Your code here

Need a hint?

Update the spec.selector.app in the service to green. Then print a confirmation message.