In the Kubernetes ecosystem, managing external access to services in a cluster is crucial for deploying reliable, secure, and scalable applications. Two fundamental components that facilitate this are Nginx Ingress and cloud provider load balancers like the Amazon Load Balancer (ALB). To understand their roles, we must take a deeper dive into how they function and interact in the Kubernetes world.

Understanding Nginx Ingress

What is Nginx Ingress?

Nginx Ingress is a Kubernetes-native method for handling inbound traffic from outside the cluster to Kubernetes services within the cluster. It operates at the application layer (Layer 7 of the OSI model) and provides many features, including:

• URL-based routing
• SSL termination
• Load balancing
• HTTP header manipulation

How Nginx Ingress Works

Nginx Ingress consists of two main components:

1. Ingress Controller: This is the actual implementation of an ingress controller, responsible for monitoring access to Ingress resources created in the cluster. For Nginx, the Nginx Ingress Controller watches for `Ingress` objects and configures its underlying Nginx proxy service accordingly.
2. Ingress Resource: This is a Kubernetes resource that defines rules for routing external HTTP/S traffic to endpoints inside the cluster.

Configuration Example

Here's a simple `Ingress` resource configuration for a domain:

• host: example.com
  • path: /
• High availability
• Automatic scaling
• Security features
• Integration with other cloud services
  • host: myapplication.example.com
    • backend:
  • Layer 7: It works primarily as an application layer load balancer, distributing HTTP/HTTPS traffic based on more sophisticated logic such as headers, paths, and cookies.
  • Flexibility: It provides advanced routing and TLS termination.
  • Not a True Load Balancer in Traditional Sense: While it performs load balancing, it doesn't manage nodes or services' health at the network layer like traditional load balancers.
  • Layer 4/7: Operate at various OSI model layers and often offer more direct integration with cloud infrastructure.
  • True Load Balancer: They balance traffic across multiple instances or containers, handle availability zones, and can integrate natively with auto-scaling features.
  • Broader Integration: Deeper access to cloud-native features not typically available to ingress controllers.