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Ingress vs Service

Hands-on example​

Assume:

  • A working Kubernetes cluster
  • An Ingress controller is installed
  • kubectl is configured

Initial state​

No Deployments, Services, or Ingresses exist.

kubectl get deployments
kubectl get svc
kubectl get ingress
No resources found in default namespace.
No resources found in default namespace.
No resources found in default namespace.

Step 1: Create a Deployment​

kubectl create deployment web --image=nginx
deployment.apps/web created

Verify.

kubectl get pods
web-6f7c8d9f6b-abcde   1/1   Running   0   5s

Step 2: Expose it with a Service​

kubectl expose deployment web --port=80
service/web exposed

Check the Service.

kubectl get svc web
NAME   TYPE        CLUSTER-IP     PORT(S)
web    ClusterIP   10.96.55.12    80/TCP

What changed:

  • Service provides a stable virtual IP

What did not change:

  • No HTTP routing exists

Step 3: Create an Ingress​

kubectl apply -f - <<EOF
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: web-ingress
spec:
  rules:
  - host: web.local
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: web
            port:
              number: 80
EOF
ingress.networking.k8s.io/web-ingress created

Check Ingress.

kubectl get ingress web-ingress
NAME          CLASS   HOSTS       ADDRESS        PORTS   AGE
web-ingress   nginx   web.local   192.168.49.2   80      10s

Step 4: Access through Ingress​

From your machine, map the host.

sudo sh -c 'echo "192.168.49.2 web.local" >> /etc/hosts'

Send a request.

curl http://web.local
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
...

What changed:

  • HTTP traffic is routed by host

What did not change:

  • Service and Pod configuration stayed the same

Key observation​

  • Services expose endpoints
  • Ingress controls HTTP routing on top of Services