Understanding Ingress in Kubernetes

In the realm of Kubernetes networking, Ingress plays a pivotal role in managing external access to services running within a cluster. In this blog post, we will delve into what Ingress is, why it is used, how it differs from other networking resources like Services, provide a basic code example, and conclude with its significance.

What is Ingress?

Ingress is a Kubernetes resource that enables external access to services within a Kubernetes cluster. It acts as a layer 7 (application layer) load balancer, routing incoming traffic to different services based on defined rules. Ingress provides features like SSL termination, virtual hosting, and path-based routing, making it a powerful tool for managing incoming traffic to your applications.

Why Use Ingress?

Ingress offers several advantages for managing external access to services:

1. Single Entry Point: Ingress provides a single entry point for external traffic into the cluster, simplifying the management of incoming connections.

2. Path-Based Routing: Ingress allows you to route traffic based on the path of the incoming request. This enables you to host multiple services on the same domain or IP address, differentiated by their paths.

3. TLS Termination: Ingress supports SSL termination, allowing you to terminate SSL/TLS connections at the edge of the cluster, offloading the decryption workload from individual services.

Difference from Services

While both Ingress and Services are Kubernetes resources for managing network traffic, they serve different purposes:

• Services: Used for internal communication between Pods within a cluster. Services provide a stable endpoint for accessing a set of Pods, typically through ClusterIP, NodePort, or LoadBalancer types.

• Ingress: Used for managing external access to services from outside the cluster. Ingress routes incoming traffic to services based on defined rules, providing features like path-based routing, SSL termination, and virtual hosting.

Basic Code Example

Here's a basic example of an Ingress manifest for routing traffic to a service:

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

This manifest defines an Ingress named my-ingress that routes traffic with the host example.com/app to the service named my-service.

Path Types in Ingress

In Kubernetes Ingress, there are three types of path matching:

1. Exact: Matches the URL path exactly.
2. Prefix: Matches based on the prefix of the URL path.
3. Implementation-Specific: Allows the Ingress controller to define its own path matching behavior. In the provided example, pathType: Prefix indicates that requests with paths starting with /app will match the rule.

Ingress Controllers and Traefik

In Kubernetes, an Ingress controller is responsible for implementing the Ingress specification and managing incoming traffic. Traefik is one such Ingress controller, known for its ease of use and rich feature set.

When using Traefik as the Ingress controller, you would typically deploy it in your cluster and configure it to watch for Ingress resources. Traefik then dynamically configures itself based on the Ingress rules defined in your Kubernetes cluster.

The IngressClassName field, introduced in Kubernetes 1.18, allows you to specify which Ingress controller should handle the Ingress resources. This helps in scenarios where multiple Ingress controllers are deployed in the cluster. For example, you could specify IngressClassName: traefik to indicate that the Traefik Ingress controller should handle the my-ingress resource.

Conclusion

Ingress is a crucial component in Kubernetes for managing external access to services within a cluster. It provides a flexible and powerful way to route incoming traffic, enabling features like path-based routing, SSL termination, and virtual hosting. By leveraging Ingress, you can efficiently manage and expose your applications to the outside world in a secure and controlled manner.