Pinter Computing

In the previous post, Learn Kubernetes part 2 – NGINX Ingress Controller, we have deployed a web application and exposed it via the kubernetes/ingress-nginx ingress controller.

In this exercise we will use Traefik, another popular proxy server. Traefik is widely used for multiple reasons: it is easier to configure, can automatically generate and renew SSL certificates using Let’s Encrypt. We will also use most of the scripts from the prior exercise.

Create the Traefik Role Based Access Control with ClusterRoleBinding. This will allow Traefik to serve all namespaces of the cluster. To restrict the Traefik to one namespace only, use the “namespace-specific RoleBindings”.

traefik-rbac.yaml (Based on https://docs.traefik.io/user-guide/kubernetes/)

---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: traefik-ingress-controller
rules:
  - apiGroups:
      - ""
    resources:
      - services
      - endpoints
      - secrets
    verbs:
      - get
      - list
      - watch
  - apiGroups:
      - extensions
    resources:
      - ingresses
    verbs:
      - get
      - list
      - watch
  - apiGroups:
    - extensions
    resources:
    - ingresses/status
    verbs:
    - update
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: traefik-ingress-controller
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: traefik-ingress-controller
subjects:
- kind: ServiceAccount
  name: traefik-ingress-controller
  namespace: kube-system

Deploy Traefik with a deployment. This introduces a few more network hops, but follows the Kubernetes best practices guidelines and provides more flexibility.

traefik-deployment.yaml (Based on https://docs.traefik.io/user-guide/kubernetes/)

---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: traefik-ingress-controller
  namespace: kube-system
---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: traefik-ingress-controller
  namespace: kube-system
  labels:
    k8s-app: traefik-ingress-lb
spec:
  replicas: 1
  selector:
    matchLabels:
      k8s-app: traefik-ingress-lb
  template:
    metadata:
      labels:
        k8s-app: traefik-ingress-lb
        name: traefik-ingress-lb
    spec:
      serviceAccountName: traefik-ingress-controller
      terminationGracePeriodSeconds: 60
      containers:
      - image: traefik
        name: traefik-ingress-lb
        ports:
        - name: http
          containerPort: 80
        - name: admin
          containerPort: 8080
        args:
        - --api
        - --kubernetes
        - --logLevel=INFO
---
kind: Service
apiVersion: v1
metadata:
  name: traefik-ingress-service
  namespace: kube-system
spec:
  selector:
    k8s-app: traefik-ingress-lb
  ports:
    - protocol: TCP
      port: 80
      name: web
    - protocol: TCP
      port: 8080
      name: admin
  type: NodePort

Create the resources

Launch the scripted resources

kubectl apply -f .

Check the Traefik pods. List the pods in the kube-system namespace, and make sure the “traefik-ingress-controller” is running.

kubectl --namespace=kube-system get pods

Expose the Traefik Web UI with a service

To be able to access the Traefik Web UI we will create a service and an ingress to expose it outside of the cluster.

ui.yaml (Based on https://docs.traefik.io/user-guide/kubernetes/)

---
apiVersion: v1
kind: Service
metadata:
  name: traefik-web-ui
  namespace: kube-system
spec:
  selector:
    k8s-app: traefik-ingress-lb
  ports:
  - name: web
    port: 80
    targetPort: 8080
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: traefik-web-ui
  namespace: kube-system
spec:
  rules:
  - host: traefik-ui.minikube
    http:
      paths:
      - path: /
        backend:
          serviceName: traefik-web-ui
          servicePort: web

Create the resources

Launch the scripted resources

kubectl apply -f .

Check the ingress

List the cluster ingresses

kubectl get ingress --all-namespaces

NAMESPACE     NAME             HOSTS                 ADDRESS   PORTS   AGE
kube-system   traefik-web-ui   traefik-ui.minikube             80      53s

Access the Kubernetes cluster via Traefik

To be able to access the traefik-ui.minikube host we need to modify the /etc/hosts file. Add the host to the file with the localhost IP address.

echo "127.0.0.1 traefik-ui.minikube" | sudo tee -a /etc/hosts

==================================

app1-frontend-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: app1-frontend-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: app1-frontend-template-label
  template:
    metadata:
      labels:
        app: app1-frontend-template-label
    spec:
      containers:
        - name: app1-frontend-container-label
          image: nginx:1.7.9
          ports:
          - containerPort: 80

app1-frontend-service.yaml

apiVersion: v1
kind: Service
metadata:
  name: app1-frontend-service
spec:
  selector:
    app: app1-frontend-template-label
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 80

Large organizations need to control the incoming traffic to the Kubernetes cluster. The most secure way is to use an ingress controller and create an ingress to channel all incoming traffic to the cluster.

In Learn Kubernetes part 1 – Web application in a Kubernetes cluster we have created a simple web application pod and exposed it to the outside world with a service using a load balancer. We will use the files we have created in that exercise with one change. The deployment is the same:

app1-frontend-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: app1-frontend-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: app1-frontend-template-label
  template:
    metadata:
      labels:
        app: app1-frontend-template-label
    spec:
      containers:
        - name: app1-frontend-container-label
          image: nginx:1.7.9
          ports:
          - containerPort: 80

In this exercise we will expose the service via an NGINX ingress controller. Delete type: LoadBalancer in the app1-frontend-service.yaml file, so Kubernetes will use type: ClusterIP, the default value.

app1-frontend-service.yaml

apiVersion: v1
kind: Service
metadata:
  name: app1-frontend-service
spec:
  selector:
    app: app1-frontend-template-label
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 80

Create an ingress controller

In this example we will use the kubernetes/ingress-nginx ingress controller maintained by the Kubernetes community. See kubernetes/ingress-nginx NGINX Ingress Controller Installation Guide to configure the NGINX Ingress Controller in your environment.

To start the kubernetes/ingress-nginx ingress controller in any operating system, execute this command to create the ‘nginx-ingress-controller’ deployment with containers

• k8s_nginx-ingress-controller_nginx-ingress-controller
• k8s_POD_nginx-ingress-controller

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/mandatory.yaml

Based on the operating system, also execute this to create the ‘ingress-nginx’ service

On Macintosh

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/provider/cloud-generic.yaml

Verify the ingress controller installation to make sure it has successfully started

kubectl get pods --all-namespaces -l app.kubernetes.io/name=ingress-nginx --watch

NAMESPACE       NAME                                        READY   STATUS    RESTARTS   AGE
ingress-nginx   nginx-ingress-controller-86449c74bb-rlx6h   1/1     Running   0          2d4h

Script the ingress

Connect the ingress to the service

Set the name of the service in the spec: … backend: serviceName:

ingress_nginx.yaml

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: ingress
spec:
  rules:
  - http:
      paths:
      - path: /
        backend:
          serviceName: app1-frontend-service
          servicePort: 80

Create the resources

To launch the application and configure the resources to expose it outside of the Kubernetes cluster, open a terminal in the directory where you saved the files and execute

 kubectl apply -f .

Verify the ingress

List the ingresses

kubectl get ingress

NAME      HOSTS   ADDRESS     PORTS   AGE
ingress   *       localhost   80      59s

To verify the ingress execute

kubectl describe ingress MY_INGRESS_NAME

Troubleshooting Kubernetes Ingress-Nginx

See Troubleshooting Kubernetes Ingress-Nginx

See Kubernetes Ingress Controllers for more info.

Accessing the application

To access the application through the ingress, open a web browser and access the application via the ADDRESS and PORTS values: http://localhost:80

The browser will display a warning, click the Advanced button

Click the Proceed to localhost (unsafe) link

You should see the NGINX default page

Delete the resources

If you want to delete these resources from the Kubernetes cluster, execute

kubectl delete -f .

Delete the ingress controller service

kubectl delete service ingress-nginx -n ingress-nginx

Delete the deployment

kubectl delete deployment nginx-ingress-controller -n ingress-nginx

Delete the ingress-nginx service

kubectl delete -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/provider/cloud-generic.yaml

Delete the ‘nginx-ingress-controller’ deployment

kubectl delete -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/mandatory.yaml

Check if all ingress pods are deleted

kubectl get pods --all-namespaces -l app.kubernetes.io/name=ingress-nginx --watch

Next: Learn Kubernetes part 3 – Traefik Ingress Controller