Introduction to Kubernetes Ingress

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Dailyk8s
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Introduction

Kubernetes is a popular open-source container orchestration platform that allows developers to deploy and manage containerized applications at scale. Ingress is a Kubernetes feature that allows external traffic to access the applications running within a cluster. In this article, we will delve into the details of Ingress, including its prerequisites, components, and configuration.

Prerequisites

Before we dive into the details of Ingress, it is important to have a basic understanding of Kubernetes and its components. If you are new to Kubernetes, you may want to familiarize yourself with Pods, Services, Deployments etc.

What is Ingress

Ingress is a Kubernetes resource that allows external traffic to access the applications running within a cluster. It acts as a reverse proxy and routes traffic to the appropriate Service based on the incoming request's hostname and path.

Ingress is implemented as a collection of rules that define how external traffic should be routed to the Services within a cluster. These rules are defined using Ingress resources, which are created and managed using the Kubernetes API.

Ingress Resource

An Ingress resource is a collection of rules that define how external traffic should be routed to the Services within a cluster. It consists of the following fields:

  • apiVersion: The API version of the Ingress resource.

  • kind: The kind of resource, which is Ingress in this case.

  • metadata: Metadata about the Ingress resource, including its name and namespace.

  • spec: The specification of the Ingress resource, including the rules for routing traffic.

Here is an example of an Ingress resource that routes traffic to two different Services based on the incoming request's hostname:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
  namespace: default
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
  - host: example.com
    http:
      paths:
      - backend:
          serviceName: service-1
          servicePort: 80
  - host: example.org
    http:
      paths:
      - backend:
          serviceName: service-2
          servicePort: 80

When do you need Ingress

You may need Ingress if you have multiple Services that need to be accessed from the outside world, or if you want to expose your application to the internet using a custom domain name.

For example, if you have a microservice-based application with multiple Services, you can use Ingress to route traffic to the appropriate Service based on the incoming request's hostname and path.

Ingress Controllers

Ingress is implemented as a collection of rules that define how external traffic should be routed to the Services within a cluster. However, these rules need to be enforced by a component called an Ingress controller.

An Ingress controller is a piece of software that reads the Ingress resources and converts them into the configuration required by a specific load balancer. There are several Ingress controllers available today, for example, NGINX, HAProxy, and Traefik.

Default Backend

Ingress resources allow you to specify rules for routing traffic to specific Services based on the incoming request's hostname and path. However, what happens if a request does not match any of the defined rules?

In such cases, you can specify a default backend that will handle all traffic that does not match any of the rules. The default backend is typically a Service that returns a 404 error or a custom error page.

Routing Use Cases

Here are some common use cases for routing traffic using Ingress:

  • Routing traffic to multiple Services based on the incoming request's hostname and path.

  • Exposing multiple Services using a single IP address and DNS name.

  • Enforcing HTTPS for all traffic.

  • Redirecting HTTP traffic to HTTPS.

  • Load balancing traffic between multiple replicas of a Service.

Configuring TLS Certificates

Ingress resources allow you to enforce HTTPS for all traffic by specifying a TLS certificate. To configure a TLS certificate, you need to do the following:

  1. Obtain a TLS certificate from a certificate authority (CA) or generate a self-signed certificate.

  2. Create a Kubernetes Secret that contains the TLS certificate and private key.

  3. Specify the Secret in the Ingress resource's spec.tls field.

Here is an example of an Ingress resource that enforces HTTPS for all traffic using a Secret named example-tls:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
  namespace: default
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  tls:
  - secretName: example-tls
  rules:
  - host: example.com
    http:
      paths:
      - backend:
          serviceName: service-1
          servicePort: 80

Conclusion

In this article, we have covered the basics of Ingress in Kubernetes, including its prerequisites, components, and configuration. We have also discussed some common use cases for routing traffic using Ingress, as well as how to configure TLS certificates for enforcing HTTPS. With this knowledge, you should be able to use Ingress to expose your applications to the outside world and route traffic to the appropriate Services within your cluster.

ingressnetworkingKubernetesTLS