Networking with Ingress on Kubernetes

Introduction

In this lab, you will learn how to use Ingress to route external traffic to services running in a Kubernetes cluster.

Kubernetes Ingress is a powerful tool for managing external access to services in a Kubernetes cluster. Ingress acts as a layer 7 load balancer, allowing you to route traffic to different services based on the incoming URL path or hostname.

In this lab, we will create a sample application and expose it to the outside world using Ingress. We will use nginx-ingress as the Ingress controller, which is a popular and widely-used solution for Kubernetes Ingress.

Start the Minikube Cluster

Before creating resources, you need a running Kubernetes cluster. Minikube is a lightweight Kubernetes environment that runs on your local machine.

Navigate to your working directory:

Open the terminal and navigate to the default project folder:
```
cd /home/labex/project
```
Start Minikube:

Start Minikube to initialize a Kubernetes cluster:
```
minikube start
```
- This command sets up a single-node Kubernetes cluster on your local machine.
- Minikube may take a few minutes to start depending on your system's performance.
Verify Minikube is running:

Check the status of the Minikube cluster:
```
minikube status
```
- Look for components like kubelet and apiserver listed as Running.
- If the cluster is not running, rerun minikube start.

If you encounter issues starting Minikube. Use minikube delete to reset the environment if needed.

Install the Nginx Ingress Controller

First, we need to install the nginx-ingress controller in our cluster. We can do this by creating a Deployment and a Service that will be responsible for running the Ingress controller.

Create a namespace for the Ingress controller:

kubectl create namespace ingress-nginx

Install the ingress-nginx chart using kubectl:

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.7.0/deploy/static/provider/cloud/deploy.yaml

Verify that the ingress-nginx controller pods are running:

kubectl get pods -n ingress-nginx

NAME                                        READY   STATUS              RESTARTS   AGE
ingress-nginx-admission-create-zjfqx        0/1     ContainerCreating   0          2s
ingress-nginx-admission-patch-8rvzw         0/1     ContainerCreating   0          2s
ingress-nginx-controller-6bdb654777-qz8fb   0/1     ContainerCreating   0          2s

Create a Sample Application

Next, we will create a sample application that we will expose using Ingress.

Create a Deployment for a sample application:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: sample-app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: sample-app
  template:
    metadata:
      labels:
        app: sample-app
    spec:
      containers:
      - name: sample-app
        image: nginx
        ports:
        - containerPort: 80

The YAML file called sample-app.yaml. Apply the deployment to your cluster with the following command:

kubectl apply -f sample-app.yaml

Create a Service for the sample application:

apiVersion: v1
kind: Service
metadata:
  name: sample-app
spec:
  selector:
    app: sample-app
  ports:
  - name: http
    port: 80
    targetPort: 80

The YAML file called service-sample-app.yaml. Apply the deployment to your cluster with the following command:

kubectl apply -f service-sample-app.yaml

Create an Ingress Resource

Now that we have the Ingress controller set up and a backend service running, we can create the rules for the Ingress resource.

In this example, we will create a simple rule to route traffic for the test.local domain to our backend service:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: test-ingress
  annotations:
    kubernetes.io/ingress.class: nginx
spec:
  rules:
  - host: test.local
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: sample-app
            port:
              name: http

The YAML file called ingress.yaml. Apply the Ingress resource to the cluster:

kubectl apply -f ingress.yaml

Test the Ingress Resource

Finally, we can test the Ingress resource to make sure everything is working correctly.

First, determine the IP address of the node:

kubectl get node -o wide

NAME       STATUS   ROLES           AGE   VERSION   INTERNAL-IP    EXTERNAL-IP   OS-IMAGE             KERNEL-VERSION      CONTAINER-RUNTIME
minikube   Ready    control-plane   93s   v1.26.1   192.168.49.2   <none>        Ubuntu 20.04.5 LTS   5.15.0-56-generic   docker://20.10.23

This command will get the kubernetes node address, The IP address labeled as INTERNAL-IP.

Next, add an entry to your /etc/hosts file to map the test.local domain to the IP address of the node:

echo "<IP_ADDRESS> test.local" | sudo tee -a /etc/hosts

Replace <IP_ADDRESS> with the internal IP address of the node address. For example:

echo "192.168.49.2 test.local" | sudo tee -a /etc/hosts

Then, get service nodeport for ingress-nginx.

kubectl get services -n ingress-nginx

This command will dcurisplay a list of services in the ingress-nginx namespace. Look for the nginx-ingress-controller service and note its NodePort.

NAME                                 TYPE           CLUSTER-IP      EXTERNAL-IP   PORT(S)                      AGE
ingress-nginx-controller             LoadBalancer   10.104.99.158   <pending>     80:32518/TCP,443:31620/TCP   2m45s
ingress-nginx-controller-admission   ClusterIP      10.100.46.109   <none>        443/TCP                      2m45s

Finally, use curl to make an HTTP request to the Ingress endpoint:

curl test.local:NodePort

For example:

curl test.local:32518

Replace <NodePort> with the NodePort of the nginx-ingress-controller service.

If everything is set up correctly, you should see the Nginx welcome page.

You can also test the Ingress by using a web browser to visit test.local:<NodePort>/nginx.

Congratulations, you have successfully set up an Ingress resource in Kubernetes and tested it to ensure that it is working correctly.

Summary

In this lab, we walked through the process of setting up and configuring an Nginx ingress controller in Kubernetes. We also created a sample application and used Ingress to route external traffic to our Nginx service. This is just the beginning of what you can do with Kubernetes networking, and we encourage you to explore further.