CKAD-journey

🚀 Simple Web App Canary Deployment Example

5-minute demo of basic Kubernetes canary deployment concepts

🎯 What You’ll Learn

Basic canary deployment with 2 application versions
Traffic routing with Kubernetes Services
Label-based pod selection
Manual traffic migration process

🗺 Architecture

[Users] → [LoadBalancer] → [Service] → [Pods v1.0 + v2.0]
                                      ↑
                                 Label Selector
                                      ↑
                            "app.kubernetes.io/name: webapp"
                         "app.kubernetes.io/version: v1.0 OR v2.0"

🛠 Prerequisites

# Verify cluster access
kubectl cluster-info

# Check kubectl version
kubectl version --client

🚀 Quick Start (5 minutes)

Step 1: Deploy the Application

# Clone the repository (if not already done)
git clone https://github.com/Salwan-Mohamed/CKAD-journey.git
cd CKAD-journey/Master-Canary-Deployments/examples/simple-webapp

# Deploy all resources
kubectl apply -f .

# Verify deployment
kubectl get all -n canary-demo

Expected Output:

NAME                            READY   STATUS    RESTARTS   AGE
pod/webapp-v1-xxxxx-xxxxx      1/1     Running   0          30s
pod/webapp-v1-xxxxx-yyyyy      1/1     Running   0          30s
pod/webapp-v1-xxxxx-zzzzz      1/1     Running   0          30s
pod/webapp-v2-xxxxx-aaaaa      1/1     Running   0          30s

NAME                    TYPE           CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
service/webapp-service  LoadBalancer   10.245.xxx.xxx  <pending>     80:30001/TCP   30s

NAME                        READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/webapp-v1   3/3     3            3           30s
deployment.apps/webapp-v2   1/1     1            1           30s

Step 2: Test Initial Setup (100% v1.0)

# Check current service configuration
kubectl describe service webapp-service -n canary-demo

# Test from inside cluster
kubectl run client --image=curlimages/curl --rm -it --restart=Never --namespace=canary-demo -- sh

# Inside the client pod:
for i in {1..10}; do
  curl -s http://webapp-service.canary-demo.svc.cluster.local | grep -o "Version [0-9.]*"
done

# Expected: All responses show "Version 1.0"
exit

Step 3: Begin Canary Deployment (25% v2.0)

# Update service to route to both versions
kubectl patch service webapp-service -n canary-demo -p='{
  "spec": {
    "selector": {
      "app.kubernetes.io/name": "webapp"
    }
  }
}'

# Verify traffic distribution
kubectl run client --image=curlimages/curl --rm -it --restart=Never --namespace=canary-demo -- sh

# Inside the client pod:
echo "Testing traffic distribution:"
for i in {1..20}; do
  curl -s http://webapp-service.canary-demo.svc.cluster.local | grep -o "Version [0-9.]*"
done | sort | uniq -c

# Expected output (approximately):
#   15 Version 1.0
#    5 Version 2.0
exit

Step 4: Increase Canary Traffic (50% v2.0)

# Scale up v2 to match v1
kubectl scale deployment webapp-v2 --replicas=3 -n canary-demo

# Wait for pods to be ready
kubectl wait --for=condition=ready pod -l app.kubernetes.io/version=v2.0 -n canary-demo --timeout=60s

# Test new distribution
kubectl run client --image=curlimages/curl --rm -it --restart=Never --namespace=canary-demo -- sh

# Inside the client pod:
for i in {1..20}; do
  curl -s http://webapp-service.canary-demo.svc.cluster.local | grep -o "Version [0-9.]*"
done | sort | uniq -c

# Expected output (approximately):
#   10 Version 1.0
#   10 Version 2.0
exit

Step 5: Complete Migration (100% v2.0)

# Route all traffic to v2.0
kubectl patch service webapp-service -n canary-demo -p='{
  "spec": {
    "selector": {
      "app.kubernetes.io/name": "webapp",
      "app.kubernetes.io/version": "v2.0"
    }
  }
}'

# Test final state
kubectl run client --image=curlimages/curl --rm -it --restart=Never --namespace=canary-demo -- sh

# Inside the client pod:
for i in {1..10}; do
  curl -s http://webapp-service.canary-demo.svc.cluster.local | grep -o "Version [0-9.]*"
done

# Expected: All responses show "Version 2.0"
exit

Step 6: Cleanup Old Version

# Scale down v1 deployment
kubectl scale deployment webapp-v1 --replicas=0 -n canary-demo

# Verify final state
kubectl get pods -n canary-demo

# Optional: Delete v1 deployment entirely
# kubectl delete deployment webapp-v1 -n canary-demo

🔍 Monitoring and Verification

Check Pod Distribution

# View all pods with labels
kubectl get pods -n canary-demo --show-labels

# Count pods by version
echo "V1 Pods:"
kubectl get pods -n canary-demo -l app.kubernetes.io/version=v1.0 --no-headers | wc -l

echo "V2 Pods:"
kubectl get pods -n canary-demo -l app.kubernetes.io/version=v2.0 --no-headers | wc -l

Service Endpoint Analysis

# Check which pods are serving traffic
kubectl get endpoints webapp-service -n canary-demo -o yaml

# Describe service for detailed info
kubectl describe service webapp-service -n canary-demo

Real-time Traffic Monitoring

# Monitor traffic in real-time
kubectl run traffic-monitor --image=curlimages/curl --rm -it --restart=Never --namespace=canary-demo -- sh -c '
v1_count=0
v2_count=0
echo "Starting traffic monitoring... (Press Ctrl+C to stop)"
while true; do
  response=$(curl -s http://webapp-service.canary-demo.svc.cluster.local | grep -o "Version [0-9.]*")
  if echo "$response" | grep -q "Version 1.0"; then
    v1_count=$((v1_count + 1))
    echo "$(date +%H:%M:%S) - V1.0 | Total: v1=$v1_count, v2=$v2_count"
  elif echo "$response" | grep -q "Version 2.0"; then
    v2_count=$((v2_count + 1))
    echo "$(date +%H:%M:%S) - V2.0 | Total: v1=$v1_count, v2=$v2_count"
  fi
  sleep 1
done'

🚨 Rollback Procedure

If you need to rollback to v1.0:

# Emergency rollback to v1.0
kubectl patch service webapp-service -n canary-demo -p='{
  "spec": {
    "selector": {
      "app.kubernetes.io/name": "webapp",
      "app.kubernetes.io/version": "v1.0"
    }
  }
}'

# Scale up v1 if needed
kubectl scale deployment webapp-v1 --replicas=3 -n canary-demo

# Scale down v2
kubectl scale deployment webapp-v2 --replicas=0 -n canary-demo

echo "Rollback completed - all traffic routed to v1.0"

🐛 Troubleshooting

Issue: Pods Not Starting

# Check pod status
kubectl describe pods -n canary-demo

# Check events
kubectl get events -n canary-demo --sort-by='.lastTimestamp'

# Check resource usage
kubectl top nodes

Issue: No Traffic to Canary

# Verify service selector
kubectl get service webapp-service -n canary-demo -o yaml | grep -A 10 selector

# Check pod labels
kubectl get pods -n canary-demo --show-labels

# Test direct pod access
POD_IP=$(kubectl get pod -l app.kubernetes.io/version=v2.0 -n canary-demo -o jsonpath='{.items[0].status.podIP}')
kubectl run test --image=curlimages/curl --rm -it --restart=Never -- curl $POD_IP

Issue: External Access Not Working

# Check LoadBalancer status
kubectl get service webapp-service -n canary-demo

# If using cloud provider, check external IP assignment
kubectl describe service webapp-service -n canary-demo

# Alternative: Use port forwarding for testing
kubectl port-forward service/webapp-service 8080:80 -n canary-demo
# Then access http://localhost:8080

🔄 Cleanup

# Delete all resources
kubectl delete namespace canary-demo

# Or delete individual resources
kubectl delete -f . --namespace=canary-demo

🎓 Key Learning Points

Label Selectors: Services use label selectors to route traffic to specific pods
Gradual Migration: Change replica counts to adjust traffic distribution
Zero Downtime: Both versions run simultaneously during migration
Easy Rollback: Simply change service selector back to stable version
Monitoring: Always verify traffic distribution during deployment

🚀 Next Steps

After completing this example:

Advanced Examples - More complex scenarios
Istio Integration - Service mesh traffic management
Monitoring Setup - Add observability
CI/CD Integration - Automate deployments

🎉 Congratulations! You’ve successfully completed your first Kubernetes canary deployment!

This example provides the foundation for understanding more advanced canary deployment patterns.