Understanding Load Balancer Service vs. Ingress in Kubernetes

Kubernetes offers multiple ways to expose your applications to the outside world, with Load Balancer service types and Ingress being two powerful options. Let's break down their differences, use cases, and limitations in a way that's easy to understand.

Load Balancer Service Type: The Direct Approach

A LoadBalancer service type in Kubernetes is like giving each of your applications its own dedicated front door to the internet.

How Load Balancer Services Work

When you create a LoadBalancer service, Kubernetes automatically provisions an external load balancer from your cloud provider (like AWS, GCP, or Azure). This load balancer gets its own unique IP address and routes external traffic directly to your application pods.

Example of a Load Balancer Service

yamlapiVersion: v1
kind: Service
metadata:
  name: my-webapp
spec:
  type: LoadBalancer
  ports:
    - port: 80
      targetPort: 8080
  selector:
    app: my-webapp

With this configuration:

• An external load balancer is provisioned with a public IP address

• External traffic to this IP on port 80 is routed to port 8080 on your application pods

• The service automatically selects pods with the label app: my-webapp

When to Use Load Balancer Services

• For simple applications that need direct external access

• When you need a dedicated IP address for each service

• When you don't need advanced routing features

• For quick and straightforward setups

Limitations of Load Balancer Service Type in AWS

While Load Balancer services are convenient, they come with several significant limitations when used in AWS:

1. Cost Inefficiency

Each LoadBalancer service creates a separate AWS ELB/NLB, and you pay for each one individually. If you have 10 services exposed this way, you're paying for 10 load balancers!

2. IP Address Limitations

AWS has quotas on how many Elastic IPs and load balancers you can provision per region. For large applications with many microservices, you might hit these limits.

3. Limited Routing Capabilities

AWS load balancers provisioned this way offer basic traffic routing. They don't provide path-based or host-based routing out of the box.

4. SSL/TLS Management Challenges

You'll need to manage SSL certificates separately for each load balancer, which becomes cumbersome as your application grows.

5. No HTTP/HTTPS Integration

Basic AWS load balancers don't offer HTTP-level features like redirects, rewrites, or session affinity without additional configuration.

Ingress: The Smart Traffic Controller

Ingress acts like an intelligent traffic controller sitting in front of multiple services, directing requests to the appropriate backend based on rules you define.

How Ingress Works

An Ingress is not a service type but a higher-level resource that provides HTTP/HTTPS routing, SSL termination, and name-based virtual hosting. It works with an Ingress Controller (like NGINX, Traefik, or AWS ALB Ingress Controller) which is responsible for fulfilling the Ingress rules.

Example of Ingress Configuration

yamlapiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-ingress
  annotations:
    kubernetes.io/ingress.class: "nginx"
spec:
  rules:
  - host: api.myapp.com
    http:
      paths:
      - path: /users
        pathType: Prefix
        backend:
          service:
            name: user-service
            port:
              number: 80
      - path: /products
        pathType: Prefix
        backend:
          service:
            name: product-service
            port:
              number: 80
  - host: store.myapp.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: store-frontend
            port:
              number: 80
  tls:
  - hosts:
      - api.myapp.com
      - store.myapp.com
    secretName: myapp-tls-cert

In this example:

• Traffic to api.myapp.com/users routes to the user-service

• Traffic to api.myapp.com/products routes to the product-service

• Traffic to store.myapp.com routes to the store-frontend service

• TLS termination is handled with a certificate stored in the myapp-tls-cert secret

When to Use Ingress

• When exposing multiple services under the same IP address

• When you need path-based or host-based routing

• When you want centralized SSL/TLS termination

• For production-grade applications with multiple microservices

• When you need advanced HTTP features like rewrites, redirects, or cors

Comparison: Load Balancer vs. Ingress

Best Practices for AWS Kubernetes Deployments

To overcome the limitations of LoadBalancer services in AWS:

1. Use an Ingress Controller with AWS ALB: The AWS ALB Ingress Controller integrates with AWS Application Load Balancers, providing advanced routing while being cloud-native.

2. Implement a Service Mesh: Consider technologies like Istio or Linkerd for complex routing needs, especially for internal service-to-service communication.

3. NodePort + External Load Balancer: For non-HTTP protocols, use NodePort services behind a manually configured AWS load balancer.

4. Leverage AWS Route53 for DNS: Combined with Ingress, this provides flexible routing to your services.

Conclusion

While LoadBalancer services offer simplicity, they can become costly and limiting in AWS environments as your application grows. Ingress provides a more scalable, cost-effective solution for HTTP/HTTPS traffic with advanced routing capabilities.

For most production workloads on AWS, using an Ingress controller with carefully planned routing rules will save costs and provide greater flexibility compared to creating individual LoadBalancer services for each application component.

Choose LoadBalancer services for simple deployments or non-HTTP protocols, and migrate to Ingress as your application grows in complexity.