Ingress vs Load Balancer: Choosing the Right Tool

• Introduction
• Step-by-Step Guide
• Code Example
• Additional Notes
• Summary
• Conclusion
• References

In Kubernetes, both Ingress and Load Balancers play crucial roles in managing network traffic, but they have distinct purposes. Load Balancers act like traffic cops, efficiently distributing incoming requests to different pods within your cluster. While Ingress functions as a receptionist, directing traffic to specific services based on rules like hostnames or paths.

In Kubernetes, both Ingress and Load Balancers help manage network traffic, but they serve different purposes.

Think of a Load Balancer as a traffic cop directing cars (requests) to different parking spots (pods) within a parking lot (cluster).

apiVersion: v1
kind: Service
metadata:
  name: my-loadbalancer
spec:
  type: LoadBalancer
  selector:
    app: my-app
  ports:
  - protocol: TCP
    port: 80
    targetPort: 8080

This code creates a Load Balancer that distributes incoming traffic on port 80 to pods with the label "app: my-app" on port 8080.

An Ingress is like a receptionist in a building, directing visitors (traffic) to specific offices (services) based on their names or departments (hostnames or paths).

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

This code defines an Ingress rule that forwards traffic from "example.com" to the "my-service" service on port 80.

Key Differences:

• Load Balancers operate at the transport layer (TCP/UDP), while Ingress works at the application layer (HTTP/HTTPS).
• Load Balancers expose services externally, often getting their own IP address. Ingress sits behind a Load Balancer or NodePort and routes traffic internally.
• Ingress offers more advanced routing capabilities based on paths, headers, etc., while Load Balancers primarily distribute traffic evenly.

In essence, use a Load Balancer to expose a service externally and an Ingress to manage traffic routing within your cluster based on HTTP/HTTPS rules.

This code demonstrates how to expose two Kubernetes services (frontend and backend) externally using Load Balancers and Ingress. It deploys frontend and backend applications with multiple replicas for redundancy and exposes them using LoadBalancer services. An Ingress resource is then defined to route traffic based on the hostname, directing requests to www.example.com to the frontend service and requests to api.example.com to the backend service. This setup ensures even traffic distribution, external accessibility, and a single entry point for managing external traffic.

This example demonstrates the difference between Load Balancers and Ingress in Kubernetes, using a simple web application scenario.

Scenario:

We have a web application with two services:

• frontend: Serves the website's static content (HTML, CSS, JS).
• backend: Handles API requests.

We want to:

1. Expose both services externally using different subdomains:
   • www.example.com for the frontend.
   • api.example.com for the backend.
2. Distribute incoming traffic to multiple instances of each service for redundancy and scalability.

Solution:

We'll use a combination of Load Balancers and Ingress:

1. Load Balancers:

   • Create a Load Balancer for the frontend service, exposing it on port 80.
   • Create a Load Balancer for the backend service, exposing it on port 80.

2. Ingress:

   • Configure an Ingress rule to route traffic from www.example.com to the frontend service.
   • Configure another Ingress rule to route traffic from api.example.com to the backend service.

Code:

1. Deployments and Services:

# frontend deployment
apiVersion: apps/v1
kind: Deployment
metadata:
  name: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      app: frontend
  template:
    metadata:
      labels:
        app: frontend
    spec:
      containers:
      - name: frontend
        image: nginx:latest
        ports:
        - containerPort: 80

# frontend service
apiVersion: v1
kind: Service
metadata:
  name: frontend-service
spec:
  type: LoadBalancer
  selector:
    app: frontend
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

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

# backend service
apiVersion: v1
kind: Service
metadata:
  name: backend-service
spec:
  type: LoadBalancer
  selector:
    app: backend
  ports:
  - protocol: TCP
    port: 80
    targetPort: 80

2. Ingress:

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

Explanation:

• We define deployments for both frontend and backend services, each with multiple replicas for redundancy.
• We create LoadBalancer services for both deployments, exposing them on port 80. This allows external access to the services.
• We define an Ingress resource with two rules:
  • The first rule routes traffic from www.example.com to the frontend-service.
  • The second rule routes traffic from api.example.com to the backend-service.

This setup ensures that:

• Traffic is distributed evenly among the replicas of each service by the Load Balancers.
• External users can access the frontend and backend services using their respective subdomains.
• The Ingress resource acts as a single entry point for external traffic and routes it internally based on the hostnames.

This is a basic example, and you can further customize Ingress rules with path-based routing, SSL termination, and more.

Load Balancers:

• Cloud Provider Specific: The actual implementation of a Load Balancer depends on your Kubernetes environment (e.g., AWS, Google Cloud, Azure). Each cloud provider offers its own Load Balancer solution that integrates with Kubernetes.
• Cost: Load Balancers typically incur costs depending on your cloud provider's pricing model.
• External IPs: When you create a LoadBalancer service, Kubernetes requests an external IP address from your cloud provider. This IP address becomes the entry point for external traffic.

Ingress:

• Requires Ingress Controller: Ingress itself is just a set of rules. You need an Ingress Controller, like Nginx Ingress or Traefik, to listen for Ingress resources and handle the actual traffic routing.
• Flexibility: Ingress offers a wide range of features beyond basic host-based routing, including:
  • Path-based routing
  • URL rewrites
  • SSL termination
  • Traffic splitting (A/B testing, canary deployments)
• Multiple Ingress Resources: You can have multiple Ingress resources in your cluster, each managing traffic for different services or parts of your application.

General:

• NodePort vs. LoadBalancer: NodePort is another way to expose services externally, but it's less sophisticated than LoadBalancer. NodePort exposes your service on a fixed port across all nodes in your cluster, while LoadBalancer provides a dedicated external IP.
• Security: Always consider security best practices when exposing services externally. Use strong authentication, authorization, and encryption (HTTPS) to protect your applications.
• Monitoring and Logging: Monitor the health and performance of your Load Balancers and Ingress controllers to ensure smooth traffic flow and identify potential issues.

Choosing the Right Approach:

• Simple Exposure: If you just need to expose a single service externally on a static IP, a LoadBalancer service might be sufficient.
• Advanced Routing: If you need more control over traffic routing, such as path-based routing or SSL termination, Ingress is the way to go.
• Cost Optimization: Consider the cost implications of using Load Balancers, especially if you have many services to expose. Ingress can be a more cost-effective solution for managing traffic to multiple services behind a single Load Balancer.

In short: Use a Load Balancer to make your service accessible externally. Use Ingress to intelligently route traffic within your cluster based on HTTP/HTTPS criteria.

In conclusion, while both Load Balancers and Ingress manage network traffic in Kubernetes, they do so at different levels and with distinct purposes. Load Balancers handle external traffic distribution to expose services, acting as a gateway to your cluster. Ingress, on the other hand, manages internal traffic routing based on HTTP/HTTPS rules, directing requests to the appropriate services within your cluster. Choosing the right approach depends on your specific needs, with Load Balancers suitable for simple service exposure and Ingress offering more advanced routing capabilities for complex applications. Understanding the differences between these two components is crucial for designing and deploying scalable and efficient applications in Kubernetes.

• Ingress vs. Load Balancer in Kubernetes | Baeldung on Ops | Learn about different mechanisms to help manage network traffic and ensure requests get to their desired destination inside a cluster
• LoadBalancer Service and Ingress : r/kubernetes | Posted by u/pdd99 - 23 votes and 17 comments
• What is Kubernetes Ingress? Concepts and Examples | Kong Inc. | Discover Kubernetes Ingress basics and efficient ways to manage external traffic routing to services in a K8s cluster. Explore load balancing, SSL termination, and much more. Learn More!
• kubernetes - Ingress vs Load Balancer - DevOps Stack Exchange | Dec 13, 2021 ... In order to have a simple DNS zone management, you need to expose all your cluster nodes in some way and that way is with an external LoadBalancer.
• Difference Between Kubernetes Ingress And Loadbalancer ... | A Computer Science portal for geeks. It contains well written, well thought and well explained computer science and programming articles, quizzes and practice/competitive programming/company interview Questions.
• What is Ingress Load Balancer Kubernetes? | VMware | Learn the definition of Ingress Load Balancer Kubernetes and get answers to FAQs regarding: Kubernetes ingress vs load balancer and more.
• Differences between Kubernetes Ingress vs. load balancer ... | For external traffic management, IT orgs must evaluate Kubernetes Ingress vs. load balancers. Factors like traffic source and type must weigh in.
• Kubernetes NodePort vs LoadBalancer vs Ingress? When should I ... | Recently, someone asked me what the difference between NodePorts, LoadBalancers, and Ingress were. They are all different ways to get…
• Ingress | Kubernetes | Make your HTTP (or HTTPS) network service available using a protocol-aware configuration mechanism, that understands web concepts like URIs, hostnames, paths, and more. The Ingress concept lets you map traffic to different backends based on rules you define via the Kubernetes API.