Exposing Services

1. via Ingress (recommended)

In this example, we will deploy a simple nginx webserver deployment and make it accessible via ingress.
Therefore, we have to create the cluster in a way, that the internal port 80 (where the traefik ingress controller is listening on) is exposed on the host system.

  1. Create a cluster, mapping the ingress port 80 to localhost:8081

    k3d cluster create --api-port 6550 -p "8081:80@loadbalancer" --agents 2

    Good to know

    • --api-port 6550 is not required for the example to work.
      It’s used to have k3s‘s API-Server listening on port 6550 with that port mapped to the host system.
    • the port-mapping construct 8081:80@loadbalancer means:
      “map port 8081 from the host to port 80 on the container which matches the nodefilter loadbalancer“
      • the loadbalancer nodefilter matches only the serverlb that’s deployed in front of a cluster’s server nodes
        • all ports exposed on the serverlb will be proxied to the same ports on all server nodes in the cluster

  2. Get the kubeconfig file (redundant, as k3d cluster create already merges it into your default kubeconfig file)

    export KUBECONFIG="$(k3d kubeconfig write k3s-default)"

  3. Create a nginx deployment

    kubectl create deployment nginx --image=nginx

  4. Create a ClusterIP service for it

    kubectl create service clusterip nginx --tcp=80:80

  5. Create an ingress object for it by copying the following manifest to a file and applying with kubectl apply -f thatfile.yaml

    Note: k3s deploys traefik as the default ingress controller

    1. # apiVersion: networking.k8s.io/v1beta1 # for k3s < v1.19
    2. apiVersion: networking.k8s.io/v1
    3. kind: Ingress
    4. metadata:
    5.   name: nginx
    6.   annotations:
    7.     ingress.kubernetes.io/ssl-redirect: "false"
    8. spec:
    9.   rules:
    10.   - http:
    11.       paths:
    12.       - path: /
    13.         pathType: Prefix
    14.         backend:
    15.           service:
    16.             name: nginx
    17.             port:
    18.               number: 80

  6. Curl it via localhost

    curl localhost:8081/

2. via NodePort

  1. Create a cluster, mapping the port 30080 from agent-0 to localhost:8082

    k3d cluster create mycluster -p "8082:30080@agent:0" --agents 2

    • Note 1: Kubernetes’ default NodePort range is 30000-32767

    • Note 2: You may as well expose the whole NodePort range from the very beginning, e.g. via k3d cluster create mycluster --agents 3 -p "30000-32767:30000-32767@server:0" (See this video from @portainer)

      • Warning: Docker creates iptable entries and a new proxy process per port-mapping, so this may take a very long time or even freeze your system!

      … (Steps 2 and 3 like above) …

  2. Create a NodePort service for it by copying the following manifest to a file and applying it with kubectl apply -f

    1. apiVersion: v1
    2. kind: Service
    3. metadata:
    4.   labels:
    5.     app: nginx
    6.   name: nginx
    7. spec:
    8.   ports:
    9.   - name: 80-80
    10.     nodePort: 30080
    11.     port: 80
    12.     protocol: TCP
    13.     targetPort: 80
    14.   selector:
    15.     app: nginx
    16.   type: NodePort

  3. Curl it via localhost

    curl localhost:8082/

Last update: September 17, 2021