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Introduction

In Kubernetes, an Ingress Controller is a specialized load balancer for managing external access to services within a cluster, typically HTTP and HTTPS traffic. It provides a way to define rules for routing traffic to different services based on the request's host and path.

Key Concepts

Ingress Resource: A collection of rules that allow inbound connections to reach the cluster services.
Ingress Controller: A daemon that watches the Kubernetes API server for updates to Ingress resources and configures the load balancer accordingly.

Why Use Ingress Controllers?

Centralized Management: Manage all external access to services in a single place.
Path-based Routing: Route traffic to different services based on URL paths.
Host-based Routing: Route traffic to different services based on the host header.
SSL Termination: Terminate SSL/TLS at the ingress point, reducing the need for individual services to handle encryption.

Common Ingress Controllers

NGINX Ingress Controller: A popular choice for its robustness and extensive features.
Traefik: Known for its simplicity and dynamic configuration capabilities.
HAProxy: Offers high performance and advanced load balancing features.
Istio: Provides advanced traffic management, security, and observability.

Setting Up an Ingress Controller

Step 1: Install the Ingress Controller

For this example, we'll use the NGINX Ingress Controller.

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/main/deploy/static/provider/cloud/deploy.yaml

Step 2: Verify the Installation

Check that the Ingress Controller pods are running:

kubectl get pods -n ingress-nginx

You should see something like:

NAME                                        READY   STATUS    RESTARTS   AGE
ingress-nginx-controller-5d5b6d5b6d-abcde   1/1     Running   0          2m

Step 3: Create an Ingress Resource

Create a file named ingress.yaml with the following content:

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

Apply the Ingress resource:

kubectl apply -f ingress.yaml

Step 4: Update DNS

Ensure that the DNS for example.com points to the external IP of the Ingress Controller. You can find the external IP by running:

kubectl get services -o wide -w -n ingress-nginx

Practical Example

Let's create a simple web application and expose it using an Ingress resource.

Step 1: Deploy a Sample Application

Create a deployment for a sample web application:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webapp
spec:
  replicas: 2
  selector:
    matchLabels:
      app: webapp
  template:
    metadata:
      labels:
        app: webapp
    spec:
      containers:
      - name: webapp
        image: nginx
        ports:
        - containerPort: 80

Apply the deployment:

kubectl apply -f webapp-deployment.yaml

Create a service to expose the deployment:

apiVersion: v1
kind: Service
metadata:
  name: webapp-service
spec:
  selector:
    app: webapp
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: ClusterIP

Apply the service:

kubectl apply -f webapp-service.yaml

Step 2: Create an Ingress Resource

Create an Ingress resource to expose the web application:

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

Apply the Ingress resource:

kubectl apply -f webapp-ingress.yaml

Step 3: Test the Ingress

Update your local /etc/hosts file to point webapp.example.com to the external IP of the Ingress Controller. Then, open a browser and navigate to http://webapp.example.com. You should see the default NGINX welcome page.

Exercises

Exercise 1: Create an Ingress Resource

Deploy a new application using the following image: httpd:latest.
Create a service to expose the application on port 80.
Create an Ingress resource to expose the application at httpd.example.com.

Solution

Deploy the application:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: httpd
spec:
  replicas: 2
  selector:
    matchLabels:
      app: httpd
  template:
    metadata:
      labels:
        app: httpd
    spec:
      containers:
      - name: httpd
        image: httpd:latest
        ports:
        - containerPort: 80

Apply the deployment:

kubectl apply -f httpd-deployment.yaml

Create the service:

apiVersion: v1
kind: Service
metadata:
  name: httpd-service
spec:
  selector:
    app: httpd
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: ClusterIP

Apply the service:

kubectl apply -f httpd-service.yaml

Create the Ingress resource:

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

Apply the Ingress resource:

kubectl apply -f httpd-ingress.yaml

Conclusion

In this section, we covered the basics of Ingress Controllers in Kubernetes, including their purpose, common types, and how to set one up using the NGINX Ingress Controller. We also walked through a practical example of deploying a web application and exposing it using an Ingress resource. Finally, we provided an exercise to reinforce the concepts learned.

In the next section, we will delve into Network Policies and how they can be used to secure communication within your Kubernetes cluster.

Ingress Controllers

Introduction

Key Concepts

Why Use Ingress Controllers?

Common Ingress Controllers

Setting Up an Ingress Controller

Step 1: Install the Ingress Controller

Step 2: Verify the Installation

Step 3: Create an Ingress Resource

Step 4: Update DNS

Practical Example

Step 1: Deploy a Sample Application

Step 2: Create an Ingress Resource

Step 3: Test the Ingress

Exercises

Exercise 1: Create an Ingress Resource

Solution

Conclusion

Kubernetes Course

Module 1: Introduction to Kubernetes

Module 2: Core Kubernetes Components

Module 3: Configuration and Secrets Management

Module 4: Networking in Kubernetes

Module 5: Storage in Kubernetes

Module 6: Advanced Kubernetes Concepts

Module 7: Monitoring and Logging

Module 8: Security in Kubernetes

Module 9: Scaling and Performance

Module 10: Kubernetes Ecosystem and Tools

Module 11: Case Studies and Real-World Applications

Module 12: Preparing for Kubernetes Certification