Traefik is a load balancer with dynamic configuration reload that can be plugged with various backend to enable routing automatically and it work with Kubernetes.

Traefik is installed by default on k3s clusters so we could use it.

Accessing dashboard

Traefik dashboard is not exposed through the exterior of the cluster by default. We need to add a IngressRoute configuration to enable it.

apiVersion: traefik.containo.us/v1alpha1
kind: IngressRoute
metadata:
  name: traefik-external-dashboard
  namespace: kube-system
spec:
  entryPoints:
  - web
  routes:
  - kind: Rule
    match: PathPrefix(`/dashboard`) || PathPrefix(`/api`)
    services:
    - kind: TraefikService
      name: api@internal

Apply this ressource in your cluster and then test to access the Traefik dashboard on http://10.0.0.11/dashboard/#/.
You should access the traefik dashboard.

Expose a service

Let’s first create a deployment with multiple replicas.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: whoami-deployment
  labels:
    app: whoami
spec:
  replicas: 3
  selector:
    matchLabels:
      app: whoami
  template:
    metadata:
      labels:
        app: whoami
    spec:
      containers:
      - name: whoami
        image: containous/whoami:v1.5.0
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 80

Check the deployment and that all the pods are healthy.

Now that we have our application deployed, let’s create a kubernetes Service to provide an entrypoint in the server for our application.

apiVersion: v1
kind: Service
metadata:
  name: whoami-service
spec:
  selector:
    app: whoami
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80

At this point, it’s standard Kubernetes ressoucres. We created an application deployment with 3 replicas and a service to be able to communicate in the cluster with this application.
Now let’s create a specific traefik IngressRoute to expose our Service to the external world.

apiVersion: traefik.containo.us/v1alpha1
kind: IngressRoute
metadata:
  name: whoami-ingress
spec:
  entryPoints:
    - web
  routes:
  - match: PathPrefix(`/whoami`)
    kind: Rule
    services:
    - name: whoami-service
      namespace: default
      port: 80

As you can see in the apiVersion this ressources is not a standard Kubernetes one, it’s a Traefik specific one.
Kubernetes allow third party system to create and manage ressources in the cluster with a mecanism named Custom Ressource Definition. We will not cover this in this course, but you could look about it by yourself.

This ressource create a descriptor for an IngressRoute as in route for incoming traffic to define some rule and send them to a target service.
Here we defined that all request atching a path starting with /whoami should be sent to whoami-service.

We could check that our application is availble from the outside of our cluster : http://10.0.0.11/whoami
Check also the Treafik dashboard to look on how it’s configured inside Traefik.

Conclusion

We just have used a solution of Ingress controller that is available on Kubernetes. There are other solutions avaiables like NGinx, HAProxy, … You can find a more exhaustive list on the official documentation

To find more information on Traefik, please look at the official website