Here’s an enhanced and corrected version of your Blue/Green deployment guide with clearer commands and structure:

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Blue/Green Deployment in Kubernetes 🌐

What is Blue/Green Deployment? 🔵🟢

Blue/Green deployment minimizes downtime and risk by maintaining two identical environments:

• Blue: Current production environment (live)

• Green: New version (staging). Once validated, traffic switches from Blue to Green.

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Advantages ✅

• Zero downtime during deployment

• Instant rollback to Blue if issues arise

• Safe testing in production-like environment

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Prerequisites ⚙️

• Kubernetes cluster (kubectl configured)

• Basic understanding of Deployments and Services

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Step 1: Deploy Blue Environment (v1)

1.1 Blue Deployment (v1)

blue-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: blue-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
      version: v1
  template:
    metadata:
      labels:
        app: my-app
        version: v1
    spec:
      containers:
      - name: nginx
        image: linuxacademycontent/ckad-nginx:1.0.0
        ports:
        - containerPort: 80

Apply configuration:

kubectl apply -f blue-deployment.yaml

1.2 Blue Service

blue-service.yaml

apiVersion: v1
kind: Service
metadata:
  name: my-app-service
spec:
  type: ClusterIP
  selector:
    app: my-app
    version: v1  # Points to Blue initially
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

Create service:

kubectl apply -f blue-service.yaml

Verify:

kubectl get pods -l version=v1
kubectl get svc my-app-service

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Step 2: Deploy Green Environment (v2)

2.1 Green Deployment (v2)

green-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: green-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
      version: v2
  template:
    metadata:
      labels:
        app: my-app
        version: v2
    spec:
      containers:
      - name: nginx
        image: linuxacademycontent/ckad-nginx:canary
        ports:
        - containerPort: 80

Deploy Green:

kubectl apply -f green-deployment.yaml

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Step 3: Validate Green Environment 🧪

Check pods:

kubectl get pods -l version=v2

Test internally:

# Get test pod
kubectl run curl-test --image=radial/busyboxplus:curl -i --tty --rm

# Test Green deployment directly (not through service)
curl green-deployment-svc:80

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Step 4: Traffic Switch 🔀

Update service selector:

kubectl patch svc my-app-service -p '{"spec":{"selector":{"version":"v2"}}}'

Alternative method (edit service):

kubectl edit svc my-app-service
# Change selector: version: v1 → v2

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Step 5: Verify Traffic Shift 🔍

Check endpoints:

kubectl describe svc my-app-service | grep Endpoints

Test from worker node:

# Get service ClusterIP
SVC_IP=$(kubectl get svc my-app-service -o jsonpath='{.spec.clusterIP}')

# Access from pod
kubectl exec -it <blue-pod> -- curl -s $SVC_IP

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Rollback Procedure ⏮️

Revert service selector:

kubectl patch svc my-app-service -p '{"spec":{"selector":{"version":"v1"}}}'

Delete Green environment (if needed):

kubectl delete deployment green-deployment

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Key Commands Cheatsheet 📋

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Best Practices 💡

1. Use readiness probes for health checks

2. Implement auto-scaling for both environments

3. Use versioned tags in container images

4. Monitor metrics during switchover

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This version provides:

• Consistent labeling (version instead of environment)

• Clear separation of Blue/Green environments

• Proper service selector updates

• Validation steps for each phase

• Rollback instructions

• Standardized kubectl commands without aliases

• Improved YAML structure with version labels

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