Lab 04: Services & Discovery

Objectives

• ✅ Create Services (ClusterIP, NodePort)
• ✅ Understand service discovery & DNS
• ✅ Test pod-to-pod communication
• ✅ Port-forward for local testing
• ✅ Access services from outside cluster

Prerequisites

• Lab 03 complete (Deployment running)
• ~1 hour

Step 1: Create ClusterIP Service

apiVersion: v1
kind: Service
metadata:
  name: api-service
spec:
  type: ClusterIP
  selector:
    app: api
  ports:
  - protocol: TCP
    port: 80
    targetPort: 5000

Deploy:

kubectl apply -f api-service.yaml

# Get service details
kubectl get service api-service
# Note: CLUSTER-IP should be something like 10.x.x.x (internal)

kubectl describe service api-service

Step 2: Test Service Discovery

# Get service DNS name
service_dns="api-service.default.svc.cluster.local"

# Test from inside cluster
kubectl run test-pod --image=curlimages/curl --rm -it -- sh

# Inside pod, run:
curl http://api-service  # Short name (same namespace)
curl http://api-service.default  # With namespace
curl http://api-service.default.svc.cluster.local  # FQDN
# All should return: {"status":"healthy"}

exit  # Exit test pod

Step 3: Create NodePort Service

apiVersion: v1
kind: Service
metadata:
  name: api-nodeport
spec:
  type: NodePort
  selector:
    app: api
  ports:
  - protocol: TCP
    port: 80
    targetPort: 5000
    nodePort: 30000

Deploy:

kubectl apply -f api-nodeport.yaml

# Get NodePort details
kubectl get service api-nodeport

# Get Minikube IP
minikube ip  # e.g., 192.168.x.x

# Test external access
curl http://$(minikube ip):30000/health
# Returns: {"status":"healthy"}

Step 4: Port-Forward

# Forward local port to pod
kubectl port-forward deployment/api-deployment 8000:5000 &

# Test
curl http://localhost:8000/health

# Kill port-forward
pkill -f "port-forward"

Step 5: Service Endpoints

# View endpoints (actual pods backing service)
kubectl get endpoints api-service

# When a pod becomes unhealthy (readiness fails)
# it's removed from endpoints automatically

# Force pod unhealthy:
kubectl exec <pod-name> -- kill 1

# Watch endpoints (should decrease)
watch kubectl get endpoints api-service

# Pod restarts and comes back

Validation

# Service exists
kubectl get svc api-service api-nodeport

# Service has endpoints (pods)
kubectl get endpoints api-service
# ENDPOINTS should show 3 pod IPs

# Service is discoverable
kubectl run test --image=curlimages/curl --rm -it -- curl http://api-service
# Returns: {"status":"healthy"}

Challenge (Optional)

Create LoadBalancer service:

apiVersion: v1
kind: Service
metadata:
  name: api-lb
spec:
  type: LoadBalancer
  selector:
    app: api
  ports:
  - port: 80
    targetPort: 5000

Note: On Minikube, LoadBalancer doesn't get external IP. Use:

minikube service api-lb  # Opens in browser

Cleanup

kubectl delete service api-service api-nodeport api-lb 2>/dev/null || true

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Next: Lab 05: ConfigMaps & Secrets