Ingress vs LoadBalancer in Kubernetes

In Kubernetes, Ingress and LoadBalancer are both ways to expose services to external traffic, but they work differently and serve distinct purposes.

1. Ingress

• Definition: Ingress is an API object in Kubernetes that manages external access to services inside the cluster, typically HTTP and HTTPS routes.
• Purpose: It allows for more complex routing rules, like URL-based routing, SSL termination, and load balancing across multiple services.
• Use Cases:
  • When you need to expose multiple services using a single external IP.
  • When you need advanced routing, like path-based or host-based routing (e.g., example.com/api routes to one service, example.com/app routes to another).
  • When you need SSL termination to offload TLS/SSL from the application.
• How It Works: Ingress typically works in conjunction with an Ingress Controller (e.g., NGINX, Traefik). The Ingress Controller is responsible for managing traffic based on the Ingress rules defined in the cluster.
• Example:
  apiVersion: networking.k8s.io/v1
  kind: Ingress
  metadata:
    name: example-ingress
  spec:
    rules:
    - host: example.com
      http:
        paths:
        - path: /api
          pathType: Prefix
          backend:
            service:
              name: api-service
              port:
                number: 80
        - path: /app
          pathType: Prefix
          backend:
            service:
              name: app-service
              port:
                number: 80
  
• Advantages:
  • Single external IP to manage multiple services.
  • Advanced routing options (path-based, host-based).
  • SSL/TLS support via certificate management.

2. LoadBalancer

• Definition: A type of Kubernetes service that automatically provisions an external load balancer from the cloud provider to expose your application to external traffic.
• Purpose: Used to expose a single service externally using a public IP. The cloud provider's load balancer routes traffic to the Kubernetes service.
• Use Cases:
  • When you have a single service that needs external access.
  • Useful for simple use cases where one service needs a public-facing endpoint.
  • Best when you are using cloud providers (e.g., AWS, GCP, Azure) that support automatic load balancer creation.
• How It Works: When a LoadBalancer service is created, Kubernetes interacts with the cloud provider to create an external load balancer that directs traffic to the service’s pods.
• Example:
  apiVersion: v1
  kind: Service
  metadata:
    name: example-loadbalancer
  spec:
    type: LoadBalancer
    selector:
      app: my-app
    ports:
    - protocol: TCP
      port: 80
      targetPort: 8080
  
• Advantages:
  • Easy to set up for a single service.
  • Automatically provisions an external load balancer with a public IP.
  • Directly integrated with cloud providers.

Key Differences

When to Use Ingress vs LoadBalancer

• Use Ingress when:
  • You need to expose multiple services via a single external IP.
  • You need advanced routing (e.g., path-based or host-based routing).
  • You need SSL/TLS termination in Kubernetes.
• Use LoadBalancer when:
  • You want to expose a single service to the outside world.
  • You are working in a cloud environment that supports external load balancers.

In summary, Ingress provides a flexible and powerful way to manage external access to multiple services with advanced routing features, while LoadBalancer is simpler, suited for exposing a single service directly to the internet via a cloud provider's load balancing service.