No token file in the metrics adapter pod

[AlexeyRaga]

I have a K8S cluster in Azure that was created with Terraform.
Trying to deploy the metrics adapter according to the instruction, and it gets deployed, but its pod in custom-metrics namespace fails with the following log line:

unable to construct client config: unable to construct lister client config to initialize provider: open /var/run/secrets/kubernetes.io/serviceaccount/token: no such file or directory

My service accounts look like:

$ kubectl describe serviceaccounts
Name:                azure-k8s-metrics-adapter
Namespace:           custom-metrics
Labels:              app=azure-k8s-metrics-adapter
                     chart=azure-k8s-metrics-adapter-0.1.0
                     heritage=Tiller
                     release=azure-k8s-metrics-adapter
Annotations:         kubectl.kubernetes.io/last-applied-configuration:
                       {"apiVersion":"v1","kind":"ServiceAccount","metadata":{"annotations":{},"labels":{"app":"azure-k8s-metrics-adapter","chart":"azure-k8s-met...
Image pull secrets:  <none>
Mountable secrets:   azure-k8s-metrics-adapter-token-hcdq4
Tokens:              azure-k8s-metrics-adapter-token-hcdq4
Events:              <none>


Name:                default
Namespace:           custom-metrics
Labels:              <none>
Annotations:         <none>
Image pull secrets:  <none>
Mountable secrets:   default-token-2pwlk
Tokens:              default-token-2pwlk
Events:              <none>

When I look at Configuration/Secrets I see that azure-k8s-metrics-adapter (Opaque), azure-k8s-metrics-adapter-token-hcdq4 (service-account-token) and default-token-2pwlk are present.

The cluster has been created using the following expression:

resource "azurerm_kubernetes_cluster" "main" {
  name                = "${var.prefix}-cluster"
  location            = azurerm_resource_group.main.location
  resource_group_name = azurerm_resource_group.main.name
  dns_prefix          = var.prefix

  default_node_pool {
    name            = "default"
    node_count      = 1
    vm_size         = "Standard_DS2_v2"
    os_disk_size_gb = 30
    vnet_subnet_id  = azurerm_subnet.aks.id
  }

  network_profile {
    network_plugin = "azure"
  }

  addon_profile {
    aci_connector_linux {
      enabled     = true
      subnet_name = azurerm_subnet.aci.name
    }
  }

  role_based_access_control {
    enabled = true
  }

  service_principal {
    client_id     = azuread_application.main.application_id
    client_secret = azuread_service_principal_password.main.value
  }
}

Did I miss something in configuration? How do I make it work?

Kubernetes version 1.15.10:

• Running on AKS