Blue-Green Deployment

Blue-Green deployment involves maintaining two separate environments: Blue (the current production environment) and Green (the new version of the application). The key steps in a Blue-Green deployment are:

1. Prepare the Green Environment: Deploy the new version of the application to the Green environment while the Blue environment is still serving traffic.
2. Switch Traffic: Once the Green environment is ready and tested, switch the traffic from Blue to Green. This can be done by updating the service to point to the Green environment.
3. Monitor and Rollback: Monitor the Green environment for any issues. If problems arise, you can quickly switch back to the Blue environment, minimizing downtime and impact on users.
4. Clean Up: After a successful deployment and monitoring period, you can clean up the Blue environment or prepare it for the next deployment.

Example of Blue-Green Deployment

# myapp-blue.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-blue
  labels:
    app: myapp
    version: front-end
spec:
  template:
    metadata:
      name: myapp-pod
      labels:
        version: v1
    spec:
      containers:
      - name: app-container
        image: myapp-image:1.0
  replicas: 5
  selector:
    matchLabels:
      version: v1

# service-definition.yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  selector:
    version: v1

# myapp-green.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-green
  labels:
    app: myapp
    version: front-end
spec:
  template:
    metadata:
      name: myapp-pod
      labels:
        version: v2
    spec:
      containers:
      - name: app-container
        image: myapp-image:2.0
  replicas: 5
  selector:
    matchLabels:
      version: v2

Switching Traffic

To switch traffic from the Blue environment to the Green environment, you can update the service selector:

# Update service to point to the Green environment
apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  selector:
    version: v2

kubectl apply -f service-definition.yaml