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Lesson 4: Ingress Controllers & Traffic Routing

🧠 The Concept (Explain Like I'm 5)

Your Kubernetes cluster is a walled fortress. An Ingress Controller is the fortress gatekeeper. When internet traffic arrives at the gate asking for api.company.com/v1, the gatekeeper reads the map and sends the traffic to the correct internal building (Pod).

🏢 The Enterprise Context

  • AWS Load Balancer Controller: Instead of deploying NGINX inside the cluster, this controller talks to the AWS API and provisions a native AWS Application Load Balancer (ALB) outside the cluster.
  • Ingress vs Gateway API: K8s Ingress is legacy. The new enterprise standard is the Kubernetes Gateway API, which splits routing rules into separate roles (Cluster Operator vs App Developer).

🗺️ Visual Architecture: Traffic Flow (AWS ALB Controller)

flowchart TD
    User["🌍 Internet User"] --> Route53["DNS (Route53)"]
    Route53 --> ALB["AWS ALB<br/>(Managed by K8s Controller)"]

    subgraph K8s ["Kubernetes Cluster"]
        TargetGroup["Target Group / NodePort"]

        subgraph AppA ["Auth Service"]
            PodA1["Pod 1"]
            PodA2["Pod 2"]
        end

        subgraph AppB ["Payment Service"]
            PodB["Pod 1"]
        end
    end

    ALB -->|/auth| PodA1
    ALB -->|/auth| PodA2
    ALB -->|/pay| PodB