Why Azure Load Balancer gets created in AKS even though I have used AppGateway as an Ingress Control-CodePudding

I've created a Kubernetes cluster in Azure using the following Terraform. As you see clearly, I have passed the AppGateway ID to ingress_application_gateway.

# Create the Azure Kubernetes Service (AKS) Cluster
resource "azurerm_kubernetes_cluster" "kubernetes_cluster" {
  count                         = var.enable_kubernetes == true ? 1 : 0
  name                          = "aks-prjx-${var.subscription_type}-${var.environment}-${var.location}-${var.instance_number}"    
  location                      = var.location
  resource_group_name           = module.resource_group_kubernetes_cluster[0].name  # "rg-aks-spoke-dev-westus3-001"
  dns_prefix                    = "dns-aks-prjx-${var.subscription_type}-${var.environment}-${var.location}-${var.instance_number}" #"dns-prjxcluster"
  private_cluster_enabled       = false
  local_account_disabled        = true

  default_node_pool {
    name                        = "npprjx${var.subscription_type}" #"prjxsyspool" # NOTE: "name must start with a lowercase letter, have max length of 12, and only have characters a-z0-9."
    vm_size                     = "Standard_B8ms"
    vnet_subnet_id              = data.azurerm_subnet.aks-subnet.id
    # zones                     = ["1", "2", "3"]
    enable_auto_scaling         = true
    max_count                   = 3
    min_count                   = 1
    # node_count                = 3
    os_disk_size_gb             = 50
    type                        = "VirtualMachineScaleSets"
    enable_node_public_ip       = false
    enable_host_encryption      = false

    node_labels = {
      "node_pool_type"          = "npprjx${var.subscription_type}"
      "node_pool_os"            = "linux"
      "environment"             = "${var.environment}"
      "app"                     = "prjx_${var.subscription_type}_app"
    }
    tags = var.tags
  }

  ingress_application_gateway {
    gateway_id = azurerm_application_gateway.network.id
  }

  # Enabled the cluster configuration to the Azure kubernets with RBAC
  azure_active_directory_role_based_access_control { 
    managed                     = true
    admin_group_object_ids      = var.active_directory_role_based_access_control_admin_group_object_ids
    azure_rbac_enabled          = true #false
  }

  network_profile {
    network_plugin              = "azure"
    network_policy              = "azure"
    outbound_type               = "userDefinedRouting"
  }

  identity {
    type = "SystemAssigned"
  }  

  oms_agent {
    log_analytics_workspace_id  = module.log_analytics_workspace[0].id
  }

  timeouts {
    create = "20m"
    delete = "20m"
  }

  depends_on = [
    azurerm_application_gateway.network
  ]
}

I was thinking that AppGateway will be used as the Ingress Gateway. However, AKS creates the Azure Load Balancer while trying to deploy the Service like mentioned below

apiVersion: v1
kind: Service
metadata:
  name: aks-helloworld 
spec:
  type: LoadBalancer
  ports:
  - port: 80
  selector:
    app: aks-helloworld-two

Is there a reason for this Load Balancer and AppGateway not being used? I would assume that Load balancer is used for type LoadBalancer and App Gateway is used for Ingress

CodePudding user response：

I tried to reproduce the same in my environment to create a Service with Application Gateway Ingress Controller:

Since you mentioned service type: Load balancer in your yaml file, it is creating load balancing service, Inorder to create service with Application Gateway Ingress Controller without an associated Load Balancer, kindly follow the below steps.

1.First, you need to create a deployment for your application with the desired replicas and the desired image.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: test-app
spec:
 replicas: 2
 selector:
  matchLabels:
  app: nginx
template:
 metadata:
   name: test-app
   labels:
     app: nginx
   spec:
     containers:
     - name: nginx
     image: "nginx:latest"
     ports:
     - containerPort: 80

cmd to check the deployed app kubectl get deploy

enter image description here

2 Next, you can create a service for your application with type:ClusterIP.

Note: if you create a service type:LoadBalancer for your application. This service will create with Load Balancer.

apiVersion: v1
kind: Service
metadata:
    name: nginx-service
     labels:
       app: nginx
   spec:
     selector:
       app: nginx
     ports:
       - port: 80
          targetPort: 80
          protocol: TCP

Service created with type: ClusterIP.

cmd to check the service: kubectl get svc

enter image description here

Create an ingress resource for your application to route the traffic to the service

apiVersion: networking.k8s.io/v1
    kind: Ingress
    metadata:
      name: nginxapp
    annotations:
       kubernetes.io/ingress.class: azure/application-gateway
     spec:
        rules:
        - http:
         paths:
        - pathType: Exact
          path: /
          backend:
           service:
             name: nginx-service
           port:
             number: 80

Ingress created successfully.

enter image description here

Once all resources are created Application Gateway Ingress Controller will route the traffic to the service without creating an associated load balancer.

Application is running successfully with application gateway public IP.

enter image description here