What is a Kubernetes Ingress Controller — Explained Simply

You've heard about Ingress, Ingress Controllers, and LoadBalancers. They all sound similar and the Kubernetes docs don't make it easier.

Let me explain this simply.

The Problem Ingress Solves

Without Ingress, exposing apps in Kubernetes looks like this:

User → Load Balancer ($$$) → Service → Pod

Every app needs its OWN load balancer. 5 apps = 5 load balancers = 5 cloud bills.

With Ingress:

User → ONE Load Balancer → Ingress Controller → Service A (app1.com)
                                              → Service B (app2.com)
                                              → Service C (app.com/api)

One load balancer routes traffic to many services based on hostname or URL path.

What is Ingress (the object)?

An Ingress is a Kubernetes resource that defines routing rules:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-ingress
spec:
  rules:
    - host: app1.devopsboys.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: app1-service
                port:
                  number: 80
    - host: app2.devopsboys.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: app2-service
                port:
                  number: 80

This YAML says: traffic for app1.devopsboys.com goes to app1-service, traffic for app2.devopsboys.com goes to app2-service.

But here's the thing — this YAML does nothing on its own.

What is an Ingress Controller?

The Ingress object is just a config file. The Ingress Controller is the actual software that reads those rules and routes traffic.

Think of it like this:

• Ingress = the menu at a restaurant (rules)
• Ingress Controller = the waiter who actually serves food (executes rules)

Without an Ingress Controller, your Ingress objects are ignored.

Popular Ingress Controllers

Nginx Ingress Controller

Most widely used. Open source, battle-tested.

helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx
helm install ingress-nginx ingress-nginx/ingress-nginx

Traefik

Popular for its auto-discovery and dashboard. Built-in Let's Encrypt support.

helm repo add traefik https://helm.traefik.io/traefik
helm install traefik traefik/traefik

AWS ALB Ingress Controller (AWS Load Balancer Controller)

On AWS/EKS, creates real AWS Application Load Balancers for each Ingress.

Kong

API gateway features built in — rate limiting, auth, plugins.

How it Works End-to-End

1. You apply an Ingress YAML to Kubernetes
2. Ingress Controller (e.g., Nginx) watches for Ingress objects
3. Nginx config is automatically updated with the new routing rules
4. Traffic comes in → Nginx routes to the correct Service → Pod responds

When you deploy the Nginx Ingress Controller, it creates a LoadBalancer Service:

kubectl get svc -n ingress-nginx
# NAME                    TYPE           EXTERNAL-IP
# ingress-nginx-controller LoadBalancer  52.x.x.x

That external IP is your single entry point. All domain names point to it. The controller handles the rest.

TLS/HTTPS with Ingress

Add TLS to your Ingress using cert-manager (free Let's Encrypt certs):

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-ingress
  annotations:
    cert-manager.io/cluster-issuer: "letsencrypt-prod"
spec:
  tls:
    - hosts:
        - app.devopsboys.com
      secretName: app-tls-cert   # cert-manager creates this
  rules:
    - host: app.devopsboys.com
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: app-service
                port:
                  number: 80

Ingress vs LoadBalancer vs NodePort

In production, you almost always want Ingress for HTTP/HTTPS apps.

Common Beginner Mistakes

Creating Ingress without an Ingress Controller installed — rules are silently ignored, nothing works.

Forgetting to add DNS records — your Ingress rule says app.example.com but DNS still points nowhere.

Wrong pathType — Exact vs Prefix matters:

• Exact: /api only matches /api
• Prefix: /api matches /api, /api/users, /api/v2 etc.

Quick Test: Is My Ingress Controller Working?

# Check controller is running
kubectl get pods -n ingress-nginx
 
# Check it has an external IP
kubectl get svc -n ingress-nginx
 
# Check ingress rules are applied
kubectl describe ingress my-ingress
 
# Test with curl (replace with your IP)
curl -H "Host: app.devopsboys.com" http://52.x.x.x

Ingress Controllers are one of the most used components in any Kubernetes cluster. Once you understand the separation between the Ingress object (rules) and the Controller (executor), everything clicks.

Learn Kubernetes networking hands-on at KodeKloud — their K8s labs have dedicated exercises for Ingress, Services, and Network Policies with real clusters.