What is Kubernetes Ingress?

Kubernetes Ingress is a Kubernetes resource that provides an entry point for external traffic to access services running inside a Kubernetes cluster. It acts as a reverse proxy, routing incoming HTTP and HTTPS traffic to the appropriate services within the cluster based on the incoming request's hostname or path.

Ingress Components

The main components involved in Kubernetes Ingress are:

Ingress Controller: The Ingress Controller is a Kubernetes controller that watches the Ingress resources and configures the load balancer or proxy server accordingly. There are several Ingress Controller implementations available, such as NGINX Ingress Controller, Traefik, and Istio Ingress Gateway.
Ingress Resource: The Ingress resource is a Kubernetes object that defines the rules for routing incoming traffic. It specifies the host names, URL paths, and the corresponding backend services that should handle the traffic.
Backend Services: The backend services are the Kubernetes services that the Ingress routes traffic to. These services can be exposed through a deployment, a stateful set, or any other Kubernetes resource.

graph LR A[External Client] --> B[Ingress Controller] B --> C[Backend Service 1] B --> D[Backend Service 2] B --> E[Backend Service 3]

Benefits of Kubernetes Ingress

Simplified Routing: Ingress simplifies the management of external traffic to your Kubernetes services by providing a single entry point and a set of routing rules.
Load Balancing: Ingress can handle load balancing and distribute incoming traffic across multiple backend services, improving the overall scalability and availability of your application.
SSL/TLS Termination: Ingress can handle SSL/TLS termination, allowing you to manage SSL/TLS certificates centrally and offload the encryption/decryption process from your backend services.
URL Rewriting and Path-based Routing: Ingress supports URL rewriting and path-based routing, enabling you to expose multiple services through a single domain name.
Extensibility: Ingress can be extended with various features, such as authentication, rate limiting, and custom routing logic, through the use of Ingress Controller plugins or annotations.

Example Ingress Configuration

Here's an example Ingress configuration that routes traffic to two different backend services based on the incoming URL path:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  - http:
      paths:
      - path: /api
        pathType: Prefix
        backend:
          service:
            name: api-service
            port:
              number: 80
      - path: /web
        pathType: Prefix
        backend:
          service:
            name: web-service
            port:
              number: 80

In this example, the Ingress routes traffic to the api-service for requests to /api/*, and to the web-service for requests to /web/*.

Conclusion

Kubernetes Ingress provides a powerful and flexible way to manage external traffic to your Kubernetes services. By using Ingress, you can simplify the routing and load balancing of your application, as well as add additional features like SSL/TLS termination and URL rewriting. Understanding Ingress and how to configure it is an essential skill for Kubernetes administrators and developers.