Kubernetes Ingress

Kubernetes Ingress is a powerful and widely used way to manage external HTTP/HTTPS traffic into your Kubernetes cluster.

What is Kubernetes Ingress?

Ingress is an API object (kind: Ingress) that acts as a smart router for external traffic coming into your cluster. It defines rules for how HTTP and HTTPS requests should be routed to different Services inside Kubernetes.

Think of it as a reverse proxy or Layer 7 load balancer sitting at the edge of your cluster.

Why do we need Ingress?

Method	Layer	Pros	Cons
NodePort	L4	Simple	Port conflicts, not production friendly
LoadBalancer	L4	Cloud-native LB	Expensive (one per service)
Ingress	L7	Single entry point, routing, TLS	Needs an Ingress Controller

Ingress solves the problem of exposing multiple services through one single IP/domain with intelligent routing.

Key Features of Ingress

• Path-based routing (/api → backend1, /web → backend2)
• Host-based routing (app1.example.com → service A, app2.example.com → service B)
• TLS/SSL Termination
• Load balancing
• Name-based virtual hosting
• URL rewriting, redirects, rate limiting (via annotations)

How Ingress Works

1. Ingress Resource — You create a YAML file defining routing rules.
2. Ingress Controller — This is the actual software (like NGINX, Traefik, HAProxy, Istio, etc.) that implements those rules.
3. The controller watches Ingress objects in the cluster and automatically configures itself.

Important: Just creating an Ingress resource does nothing without an Ingress Controller running in the cluster.

Popular Ingress Controllers

• NGINX Ingress Controller (most popular)
• Traefik
• HAProxy
• AWS ALB Ingress Controller
• GCE Ingress Controller
• Contour
• Istio Ingress (when using service mesh)

Basic Example

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  ingressClassName: nginx          # Important in newer Kubernetes
  tls:
  - hosts:
    - example.com
    secretName: example-tls
  rules:
  - host: example.com
    http:
      paths:
      - path: /api
        pathType: Prefix
        backend:
          service:
            name: api-service
            port:
              number: 80

      - path: /
        pathType: Prefix
        backend:
          service:
            name: frontend-service
            port:
              number: 80

Ingress vs Gateway API

Kubernetes is slowly moving from Ingress to the newer Gateway API (more flexible, role-oriented, better CRDs).

Feature	Ingress	Gateway API
Maturity	Stable	Gradually maturing
Flexibility	Good	Excellent
Complexity	Simpler	More powerful
Current Adoption	Very High	Growing rapidly

---

Summary

• Ingress = Set of routing rules
• Ingress Controller = The actual proxy that applies those rules
• Best for exposing multiple HTTP applications under one or few domains with clean routing and TLS management.