How to setup host based routing in eks with ingress controller ?

Of course. To set up host-based routing in EKS, you define an Ingress resource with multiple rules. Each rule specifies a hostname (e.g., app1.example.com) and maps it to a corresponding backend Service. The AWS Load Balancer Controller reads this resource and provisions an Application Load Balancer (ALB) to route traffic based on the Host header of incoming requests.

Here’s a complete guide.

Prerequisites

A running Amazon EKS cluster.

kubectl configured to connect to your cluster.

The AWS Load Balancer Controller installed in your cluster. This is the standard Ingress controller for EKS.

A registered domain name (e.g., your-domain.com) that you can manage.

Step 1: Deploy Sample Applications

First, let's deploy two different applications to route traffic to: a "coffee" app ☕ and a "tea" app 🍵. Each application will have a Deployment and a Service.

Save the following YAML as apps.yaml:

# apps.yaml

# --- Coffee App ---

apiVersion: apps/v1

kind: Deployment

metadata:

  name: coffee-deployment

spec:

  replicas: 2

  selector:

    matchLabels:

      app: coffee

  template:

    metadata:

      labels:

        app: coffee

    spec:

      containers:

      - name: coffee-container

        image: hashicorp/http-echo:latest # A simple echo server

        args:

        - "-text=Welcome to the Coffee Service!"

        ports:

        - containerPort: 5678

---

apiVersion: v1

kind: Service

metadata:

  name: coffee-service

spec:

  type: ClusterIP

  selector:

    app: coffee

  ports:

  - protocol: TCP

    port: 80

    targetPort: 5678

---

# --- Tea App ---

apiVersion: apps/v1

kind: Deployment

metadata:

  name: tea-deployment

spec:

  replicas: 2

  selector:

    matchLabels:

      app: tea

  template:

    metadata:

      labels:

        app: tea

    spec:

      containers:

      - name: tea-container

        image: hashicorp/http-echo:latest

        args:

        - "-text=Welcome to the Tea Service!"

        ports:

        - containerPort: 5678

---

apiVersion: v1

kind: Service

metadata:

  name: tea-service

spec:

  type: ClusterIP

  selector:

    app: tea

  ports:

  - protocol: TCP

    port: 80

    targetPort: 5678

Apply this manifest to your cluster:

kubectl apply -f apps.yaml

Step 2: Create the Ingress Resource

Next, create the Ingress resource. This object defines the routing logic. The spec.rules section is where you map each hostname to its backend service.

Save the following as host-based-ingress.yaml. Remember to replace coffee.your-domain.com and tea.your-domain.com with your actual hostnames.

# host-based-ingress.yaml

apiVersion: networking.k8s.io/v1

kind: Ingress

metadata:

  name: main-ingress

  annotations:

    # This annotation specifies that the ALB should be internet-facing

    alb.ingress.kubernetes.io/scheme: internet-facing

    # This annotation directs the ALB to route traffic directly to pod IPs

    alb.ingress.kubernetes.io/target-type: ip

spec:

  # This field tells Kubernetes that the AWS Load Balancer Controller should manage this Ingress

  ingressClassName: alb

  rules:

    # Rule for requests to the coffee host

    - host: "coffee.your-domain.com"

      http:

        paths:

          - path: /

            pathType: Prefix

            backend:

              service:

                name: coffee-service # Routes traffic to the coffee-service

                port:

                  number: 80

    # Rule for requests to the tea host

    - host: "tea.your-domain.com"

      http:

        paths:

          - path: /

            pathType: Prefix

            backend:

              service:

                name: tea-service # Routes traffic to the tea-service

                port:

                  number: 80

Apply the Ingress manifest:

kubectl apply -f host-based-ingress.yaml

Step 3: Verify the Load Balancer

The AWS Load Balancer Controller will now provision an ALB in your AWS account. This can take a few minutes.

Check Ingress Status: Find the DNS address of the newly created ALB.

kubectl get ingress main-ingress

Wait until the ADDRESS column is populated with a DNS name (e.g., k8s-...-.elb.amazonaws.com).

Test Routing: Before setting up DNS, you can test the routes using curl and specifying the Host header. Let's say your ALB address is YOUR_ALB_ADDRESS.

Test the coffee route:

# Replace YOUR_ALB_ADDRESS with the address from the previous command

curl http://YOUR_ALB_ADDRESS -H "Host: coffee.your-domain.com"

This should return Welcome to the Coffee Service!.

Test the tea route:

curl http://YOUR_ALB_ADDRESS -H "Host: tea.your-domain.com"

This should return Welcome to the Tea Service!.

Step 4: Configure DNS 🌐

The final step is to point your public hostnames to the ALB.

Go to your DNS provider (e.g., Amazon Route 53, GoDaddy, Cloudflare).

Create two CNAME records:

Record 1:

Name: coffee (or coffee.your-domain.com)

Type: CNAME

Value/Target: The ALB address you got from kubectl get ingress.

Record 2:

Name: tea (or tea.your-domain.com)

Type: CNAME

Value/Target: The same ALB address.

Note: If you use Amazon Route 53, it is best practice to create an A record and use the Alias feature to point it directly to the Application Load Balancer.

After the DNS records propagate, you can access your services using their public URLs:

curl http://coffee.your-domain.com

curl http://tea.your-domain.com