Install Ingress NGINX Controller

In this section, we'll install Ingress NGINX Controller on our environment and test its functionality.
Ingress NGINX Controller enable us to use NGINX as a reverse proxy and load-balancer on K8S environment. It can receive client's response and route to connected services stably so it's effective for building a Microservice Architecture(MSA).

Download and install Helm chart

There's some other ingress controllers like nginxinc/kubernetes-ingress from NGINX Inc.,
but for here we'll use official Helm chart by Kubernetes.

Download Helm chart from following link:
https://github.com/kubernetes/ingress-nginx/

Then install chart with helm install command.

helm install ingress-nginx -n ingress-nginx ./ingress-nginx --create-namespaces

ingress-nginx-controller service is set to LoadBalancer type by default,
so we can see that external IP is allocated when service is created.

Configure static IP

In values.yaml if we configure controller.service.loadBalancerIP to the IP address that is in range of MetalLB configuration, we can fix our external IP. For example: 192.168.0.222.

Then you can update the setting using helm upgrade command.

helm upgrade ingress-nginx -n ingress-nginx ./ingress-nginx

Testing ingress controller

We'll re-create and expose NGINX application for testing.
However, there's some change: application is deployed on example namespace, and there's no LoadBalancer type on the service.

nginx-sample.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx
  labels:
    env: test
spec:
  containers:
    - name: nginx
      image: nginx
      imagePullPolicy: IfNotPresent
  nodeSelector:
    kubernetes.io/hostname: k3s-worker-2

kubectl create ns example

kubectl apply -f ./nginx-sample.yaml -n example

kubectl expose pod nginx -n example --name=lb-nginx --port=80

Currently lb-nginx service cannot be accessed from external client.
Our goal is to allocate our service to /example endpoint.

To connect lb-nginx service on ingress controller, we need to write new config file for service & ingress.
With ExternalName type we can connect service from other namespace.¹

custom-ingress.yaml

kind: Service
apiVersion: v1
metadata:
  name: example-svc
  namespace: my-ingress
spec:
  type: ExternalName
  externalName: lb-nginx.example.svc.cluster.local
  # service-name.namespace-name.svc.cluster.local
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: custom-ingress
  namespace: my-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  ingressClassName: "nginx"
  rules:
    - http:
        paths:
          - path: /example
            pathType: Prefix
            backend:
              service:
                name: example-svc
                port:
                  number: 80

2 properties highlighted in ingress setting have to be configured correctly.
We passed nginx to spec.ingressClassName because it is a default value for Ingress NGINX Controller.

> k get IngressClass --all-namespaces
NAME      CONTROLLER                      PARAMETERS   AGE
traefik   traefik.io/ingress-controller   <none>       77m
nginx     k8s.io/ingress-nginx            <none>       39m

Then create K8S objects with kubectl.

kubectl create ns my-ingress
kubectl apply -f ./custom-ingress.yaml

Navigate to external IP allocated to ingress-nginx-controller service.
It can be accessed basically, but returns 404 Not Found because we didn't configure any service on the root.

Now when we navigate to /example endpoint, we can see NGINX page like before.

Footnotes

1. https://stackoverflow.com/a/59845018 ↩