Terraform-provider-azurerm: default_node_pool availability_zones changes in "azurerm_kubernetes_cluster" does not apply correctly, it should recreate the cluster

[piraces]

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Terraform (and AzureRM Provider) Version

Terraform v0.12.28
provider.azurerm v2.18.0

Affected Resource(s)

• azurerm_kubernetes_cluster

Terraform Configuration Files

resource "azurerm_kubernetes_cluster" "aks" {
  name                    = local.aks_name
  resource_group_name     = azurerm_resource_group.core.name
  location                = azurerm_resource_group.core.location
  dns_prefix              = "${local.aks_name}-dns"
  kubernetes_version      = var.AKS_VERSION
  sku_tier                = "Free"
  private_cluster_enabled = var.AKS_AS_PRIVATE_CLUSTER

  addon_profile {
    aci_connector_linux {
      enabled = false
    }

    azure_policy {
      enabled = false
    }

    http_application_routing {
      enabled = false
    }

    kube_dashboard {
      enabled = false
    }

    oms_agent {
      enabled = false
    }
  }

  default_node_pool {
    name                 = "default"
    vm_size              = var.AKS_DEFAULT_NODE_POOL_VM_SIZE
    availability_zones   = ["1", "2", "3"]
    orchestrator_version = var.AKS_VERSION

    enable_node_public_ip = false
    enable_auto_scaling   = false
    # Only if enable_auto_scaling = false
    node_count = var.AKS_DEFAULT_NODE_POOL_NODE_COUNT
    # Only if enable_auto_scaling = true
    # max_count           = value
    # min_count           = value
    # node_count          = value

    max_pods       = var.AKS_DEFAULT_NODE_POOL_NODE_MAX_PODS
    type           = "VirtualMachineScaleSets"
    vnet_subnet_id = data.azurerm_subnet.aks-subnet.id
  }

  identity {
    type = "SystemAssigned"
  }

  network_profile {
    dns_service_ip     = var.AKS_NETWORK_DNS_SERVICE_IP
    docker_bridge_cidr = "172.17.0.1/16"
    load_balancer_sku  = "Standard"
    network_plugin     = "azure"
    outbound_type      = "loadBalancer"
    service_cidr       = var.AKS_NETWORK_SERVICE_CIDR
  }

  role_based_access_control {
    enabled = true
    azure_active_directory {
      client_app_id     = var.AKS_RBAC_CLIENT_APP_ID
      server_app_id     = var.AKS_RBAC_SERVER_APP_ID
      server_app_secret = var.AKS_RBAC_SERVER_APP_SECRET
      tenant_id         = var.AZURE_TENANT_ID
    }
  }

  tags = local.common_tags
}

Debug Output

  # azurerm_kubernetes_cluster.aks will be updated in-place
  ~ resource "azurerm_kubernetes_cluster" "aks" {
        api_server_authorized_ip_ranges = []
        dns_prefix                      = "***"
        enable_pod_security_policy      = false
        id                              = "/subscriptions/***/resourcegroups/***/providers/Microsoft.ContainerService/managedClusters/***"
        kube_admin_config               = [
            {
                client_certificate     = "***"
                client_key             = "***"
                cluster_ca_certificate = "***"
                host                   = "https://***.privatelink.northeurope.azmk8s.io:443"
                password               = "***"
                username               = "***"
            },
        ]
        kube_admin_config_raw           = (sensitive value)
        kube_config                     = [
            {
                client_certificate     = ""
                client_key             = ""
                cluster_ca_certificate = "***"
                host                   = "https://***.privatelink.northeurope.azmk8s.io:443"
                password               = ""
                username               = "***"
            },
        ]
        kube_config_raw                 = (sensitive value)
        kubelet_identity                = [
            {
                client_id                 = "***"
                object_id                 = "***"
                user_assigned_identity_id = "/subscriptions/***/resourcegroups/***/providers/Microsoft.ManagedIdentity/userAssignedIdentities/***"
            },
        ]
        kubernetes_version              = "1.17.7"
        location                        = "northeurope"
        name                            = "***"
        node_resource_group             = "***"
        private_cluster_enabled         = true
        private_fqdn                    = "***.privatelink.northeurope.azmk8s.io"
        private_link_enabled            = true
        resource_group_name             = "***"
        sku_tier                        = "Free"
        tags                            = {
            "PROJECT"       = "***"
            "IT" = "***"
        }

        addon_profile {
            aci_connector_linux {
                enabled = false
            }

            azure_policy {
                enabled = false
            }

            http_application_routing {
                enabled = false
            }

            kube_dashboard {
                enabled = false
            }

            oms_agent {
                enabled            = false
                oms_agent_identity = []
            }
        }

    ~ default_node_pool {
          ~ availability_zones    = [
              + "1",
              + "2",
              + "3",
            ]
            enable_auto_scaling   = false
            enable_node_public_ip = false
            max_count             = 0
            max_pods              = 30
            min_count             = 0
            name                  = "default"
            node_count            = 2
            node_labels           = {}
            node_taints           = []
            orchestrator_version  = "1.17.7"
            os_disk_size_gb       = 128
            tags                  = {}
            type                  = "VirtualMachineScaleSets"
            vm_size               = "Standard_DS2_v2"
            vnet_subnet_id        = "/subscriptions/***/resourceGroups/***/providers/Microsoft.Network/virtualNetworks/***/subnets/***"
        }

        identity {
            principal_id = "***"
            tenant_id    = "***"
            type         = "SystemAssigned"
        }

        network_profile {
            dns_service_ip     = "192.168.0.10"
            docker_bridge_cidr = "172.17.0.1/16"
            load_balancer_sku  = "Standard"
            network_plugin     = "azure"
            outbound_type      = "loadBalancer"
            service_cidr       = "192.168.0.0/23"

            load_balancer_profile {
                effective_outbound_ips    = [
                    "/subscriptions/***/resourceGroups/***/providers/Microsoft.Network/publicIPAddresses/***",
                ]
                idle_timeout_in_minutes   = 0
                managed_outbound_ip_count = 1
                outbound_ip_address_ids   = []
                outbound_ip_prefix_ids    = []
                outbound_ports_allocated  = 0
            }
        }

        role_based_access_control {
            enabled = true

            azure_active_directory {
                admin_group_object_ids = []
                client_app_id          = "***"
                managed                = false
                server_app_id          = "***"
                server_app_secret      = (sensitive value)
                tenant_id              = "***"
            }
        }

        windows_profile {
            admin_username = "***"
        }
    }

Panic Output

No panic output.

Expected Behavior

I expect the cluster to be recreated since availability zones cannot be changed without destroying the cluster. It should warn about the cluster recreation and create the new with the availability zones. Azure does not support changing the availability zones of a created cluster.

See limitations in the Availability Zones for AKS documentation of Microsoft here.

Actual Behavior

Terraform detect changes that could be applied to the cluster without recreating it (which is incorrect, regarding the docs).

Due to this incorrect change detection, it attempts to apply impossible changes and it results either in timeout or applying the changes without doing nothing.

Steps to Reproduce

1. terraform apply of the config file attached.
2. It detect changes as the attached output.
3. The apply sometimes results in a timeout or in "changes applied" (but there are no changes), it detect changes in subsequent terraform apply.

Important Factoids

No important Factoids.

References

No references.

[njuCZ]

@piraces thanks for pointing out this issue, I have submit a PR to make this field force new

[hashibot[bot]]

This has been released in version 2.36.0 of the provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading. As an example:

provider "azurerm" {
    version = "~> 2.36.0"
}
# ... other configuration ...

[hashibot[bot]]

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