Chapter 4 got traffic in with NodePort: one high port per Service. Real clusters publish many apps on one address, by name. That is Ingress.

Two parts

The controller is a Deployment like any other, in kube-system, with a Service in front of it. It watches Ingress objects and reconfigures itself. Without a controller, an Ingress is a routing table nobody reads.

kubectl get ingressclass
kubectl get svc -n kube-system traefik

An Ingress

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: market
spec:
  ingressClassName: traefik
  rules:
    - host: market.example
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: market-web
                port:
                  number: 80

Or in one line: kubectl create ingress market --class=traefik --rule="market.example/*=market-web:80".

Requests arriving with Host: market.example go to the market-web Service on port 80. The Service must exist in the same namespace as the Ingress, and the controller forwards to its endpoints directly.

Testing without DNS

Nothing resolves market.example yet. Send the Host header yourself:

curl -H "Host: market.example" http://10.0.0.10/
curl -H "Host: nope.example" http://10.0.0.10/

<h1>Monster Market</h1>
404 page not found

The second is Traefik's own answer: no rule matched the host.

Reading it

kubectl get ingress
kubectl describe ingress market

NAME     CLASS     HOSTS            ADDRESS     PORTS   AGE
market   traefik   market.example   10.0.0.10   80      20s

ADDRESS is where the controller listens. describe shows each rule with the backend and its current endpoint IPs; <error: services "x" not found> there is the classic typo.