EKS Ingress with Single ALB, multiple namespaces, and External DNS

I was able to make it work using only one ALB, @YYashwanth, Using Nginx was my fallback plan, I'm trying to make the configuration as simple as possible, maybe in the future when we will try to deploy our solution in other cloud providers we will use nginx ingress controller.

1- To start the service type should be node port, use loadbalancer will create a classic LB.

apiVersion: v1
kind: Service
metadata:
  name: sentinel-srv
  annotations:
    external-dns.alpha.kubernetes.io/hostname: operatorv2.dev.sentinel.mysite.io
  namespace: operatorv2-dev
  labels:
    run: jsflow-sentinel
spec:
  ports:
    - port: 80
      targetPort: 80
      name: ps1
      protocol: TCP
  selector:
    app: sentinel-app
  type: NodePort

2- Second we need to configure group.name, for the ingress controller to merge all ingress configurations using the annotation alb.ingress.kubernetes.io/group.name

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  annotations:
    alb.ingress.kubernetes.io/healthcheck-interval-seconds: "15"
    alb.ingress.kubernetes.io/healthcheck-path: /
    alb.ingress.kubernetes.io/healthcheck-port: traffic-port
    alb.ingress.kubernetes.io/healthcheck-protocol: HTTP
    alb.ingress.kubernetes.io/healthcheck-timeout-seconds: "5"
    alb.ingress.kubernetes.io/healthy-threshold-count: "2"
    alb.ingress.kubernetes.io/listen-ports: '[{"HTTP": 80} ]'
    alb.ingress.kubernetes.io/scheme: internet-facing
    alb.ingress.kubernetes.io/success-codes: "200"
    alb.ingress.kubernetes.io/tags: createdBy=aws-controller
    alb.ingress.kubernetes.io/target-type: ip
    alb.ingress.kubernetes.io/unhealthy-threshold-count: "2"
    external-dns.alpha.kubernetes.io/hostname: operatorv2.sentinel.mysite.io
    kubernetes.io/ingress.class: alb
    alb.ingress.kubernetes.io/group.name: sentinel-group
  name: dev-operatorv2-sentinel-ingress-controller
  namespace: operatorv2-dev
spec:
  rules:
    - host: operatorv2.dev.sentinel.mysite.io
      http:
        paths:
          - path: /*
            backend:
              servicePort: 80
              serviceName: sentinel-srv

A feature that was pushed out around November 2021 through the AWS ALB Ingress Controller ~v2.0 allows you to create just a single ALB for multiple Ingresses across multiple namespaces - if required by using the annotation alb.ingress.kubernetes.io/group.name: [InsertValue]

All ingress resources created with the same group.name will have the same ALB.

Unfortunately the tool being used for your usecase is wrong. AWS Load Balancer Controller will create a new load balancer for every ingress resource and I think, it makes a network load balancer for every service resource.

For your use-case, the best option is to use nginx ingress controller. You can deploy the nginx ingress controller in any 1 namespace and then create ingress resources throughout your cluster and you can have path/hostname based routing across your cluster.

In case you have many teams/projects/applications and you want to avoid a single point of failure where all your apps depend on 1 ELB, you can deploy more than 1 nginx ingress controller in your k8s cluster.

You just need to define a ingress-class variable in your nginx ingress controller deployment and add that ingress-class annotation on your applications. This way, applications having ingress-class:nginxA annotation will be clustered with the nginx ingress controller that has ingress-class=nginxA in its deployment.