Understanding AWS ALB Ingress Controller In Kubernetes: End-to-End Request Flow

The AWS ALB Ingress Controller is a critical component for managing external access to applications running on Amazon Elastic Kubernetes Service (EKS). It automates the creation and configuration of Application Load Balancers (ALBs) to route traffic to Kubernetes services based on Ingress resource definitions.

How AWS ALB Ingress Controller Works

Ingress Resource Definition: You define routing rules in a Kubernetes Ingress manifest (e.g., host-based or path-based routing).
ALB Provisioning: The controller detects the Ingress resource and automatically provisions an ALB.
Target Group Binding: The controller registers Kubernetes pods as targets in ALB target groups.
Request Handling: External traffic hits the ALB, which routes requests to the appropriate Kubernetes service based on the Ingress rules.

You Should Know:

1. Deploying the AWS ALB Ingress Controller


<h1>Install the AWS Load Balancer Controller</h1>

kubectl apply -k "github.com/aws/eks-charts/stable/aws-load-balancer-controller/crds?ref=master"

<h1>Add the EKS Helm repo</h1>

helm repo add eks https://aws.github.io/eks-charts

<h1>Install the controller</h1>

helm install aws-load-balancer-controller eks/aws-load-balancer-controller \ 
--set clusterName=<your-cluster-name> \ 
--set serviceAccount.create=false \ 
--set serviceAccount.name=aws-load-balancer-controller \ 
-n kube-system

2. Example Ingress Manifest

apiVersion: networking.k8s.io/v1 
kind: Ingress 
metadata: 
name: sample-ingress 
annotations: 
kubernetes.io/ingress.class: alb 
alb.ingress.kubernetes.io/scheme: internet-facing 
alb.ingress.kubernetes.io/target-type: ip 
spec: 
rules: 
- host: myapp.example.com 
http: 
paths: 
- path: / 
pathType: Prefix 
backend: 
service: 
name: my-service 
port: 
number: 80

3. Verifying ALB Creation


<h1>Check Ingress status</h1>

kubectl get ingress

<h1>Describe ALB details</h1>

kubectl describe ingress sample-ingress

<h1>List ALBs via AWS CLI</h1>

aws elbv2 describe-load-balancers --query "LoadBalancers[?contains(LoadBalancerName, 'k8s')].DNSName"

4. Troubleshooting Common Issues

Missing IAM Permissions: Ensure the controller has `elasticloadbalancing` permissions.
Pod Readiness: Verify pods are in `READY` state and registered as ALB targets.
Security Groups: Check if the ALB security group allows traffic on required ports.

What Undercode Say

The AWS ALB Ingress Controller simplifies Kubernetes external traffic management by automating ALB setup. Key takeaways:
– Use Helm for easy deployment.
– Annotate Ingress resources correctly (kubernetes.io/ingress.class: alb).
– Monitor ALB target health and security group rules.
– For advanced routing, explore annotations like `alb.ingress.kubernetes.io/actions` for weighted routing.