azurerm_kubernetes_cluster - fix validation logic for dns_prefix

internal/services/containers/kubernetes_cluster_resource_test.go

@@ -245,6 +245,24 @@ func (KubernetesClusterResource) updateDefaultNodePoolAgentCount(nodeCount int)
 	}
 }
 
+func TestAccKubernetesCluster_dnsPrefix(t *testing.T) {
+	// regression test case for issue #20806
+	data := acceptance.BuildTestData(t, "azurerm_kubernetes_cluster", "test")
+	dnsPrefix := fmt.Sprintf("1stCluster%d", data.RandomInteger)
+
+	r := KubernetesClusterResource{}
+
+	data.ResourceTest(t, r, []acceptance.TestStep{
+		{
+			Config: r.dnsPrefix(data, currentKubernetesVersion),
+			Check: acceptance.ComposeTestCheckFunc(
+				check.That(data.ResourceName).ExistsInAzure(r),
+				check.That(data.ResourceName).Key("dns_prefix").HasValue(dnsPrefix),
+			),
+		},
+	})
+}
+
 func (KubernetesClusterResource) hostEncryption(data acceptance.TestData, controlPlaneVersion string) string {
 	return fmt.Sprintf(`
 provider "azurerm" {
@@ -652,3 +670,35 @@ resource "azurerm_kubernetes_cluster" "test" {
 }
   `, data.RandomInteger, data.Locations.Primary, data.RandomInteger, data.RandomInteger, controlPlaneVersion)
 }
+
+func (KubernetesClusterResource) dnsPrefix(data acceptance.TestData, controlPlaneVersion string) string {
+	return fmt.Sprintf(`
+provider "azurerm" {
+  features {}
+}
+
+resource "azurerm_resource_group" "test" {
+  name     = "acctestRG-aks-%d"
+  location = "%s"
+}
+
+resource "azurerm_kubernetes_cluster" "test" {
+  name                = "acctestaks%d"
+  location            = azurerm_resource_group.test.location
+  resource_group_name = azurerm_resource_group.test.name
+  dns_prefix          = "1stCluster%d"
+  kubernetes_version  = %q
+
+  default_node_pool {
+    name                   = "default"
+    node_count             = 1
+    vm_size                = "Standard_DS2_v2"
+    enable_host_encryption = true
+  }
+
+  identity {
+    type = "SystemAssigned"
+  }
+}
+  `, data.RandomInteger, data.Locations.Primary, data.RandomInteger, data.RandomInteger, controlPlaneVersion)
+}

internal/services/containers/validate/kubernetes.go

@@ -6,33 +6,51 @@ import (
 )
 
 func KubernetesAdminUserName(i interface{}, k string) (warnings []string, errors []error) {
-	adminUserName := i.(string)
+	adminUserName, ok := i.(string)
+	if !ok {
+		return nil, []error{fmt.Errorf("expected type of %q to be string", k)}
+	}
 
-	re := regexp.MustCompile(`^[A-Za-z][-A-Za-z0-9_]*$`)
+	re := regexp.MustCompile(`^[A-Za-z][-A-Za-z\d_]*$`)
 	if re != nil && !re.MatchString(adminUserName) {
-		errors = append(errors, fmt.Errorf("%s must start with alphabet and/or continue with alphanumeric characters, underscores, hyphens. Got %q.", k, adminUserName))
+		errors = append(errors, fmt.Errorf("the %q must begin with a letter, contain only letters, numbers, underscores and hyphens, got %q", k, adminUserName))
 	}
 
 	return warnings, errors
 }
 
 func KubernetesAgentPoolName(i interface{}, k string) (warnings []string, errors []error) {
-	agentPoolName := i.(string)
+	agentPoolName, ok := i.(string)
+	if !ok {
+		return nil, []error{fmt.Errorf("expected type of %q to be string", k)}
+	}
 
-	re := regexp.MustCompile(`^[a-z]{1}[a-z0-9]{0,11}$`)
+	re := regexp.MustCompile(`^[a-z]{1}[a-z\d]{0,11}$`)
 	if re != nil && !re.MatchString(agentPoolName) {
-		errors = append(errors, fmt.Errorf("%s must start with a lowercase letter, have max length of 12, and only have characters a-z0-9. Got %q.", k, agentPoolName))
+		errors = append(errors, fmt.Errorf("the %q must begin with a lowercase letter, contain only lowercase letters and numbers and be between 1 and 12 characters in length, got %q", k, agentPoolName))
 	}
 
 	return warnings, errors
 }
 
 func KubernetesDNSPrefix(i interface{}, k string) (warnings []string, errors []error) {
-	dnsPrefix := i.(string)
+	dnsPrefix, ok := i.(string)
+	if !ok {
+		return nil, []error{fmt.Errorf("expected type of %q to be string", k)}
+	}
 
-	re := regexp.MustCompile(`^[a-zA-Z][-a-zA-Z0-9]{0,43}[a-zA-Z0-9]$`)
-	if re != nil && !re.MatchString(dnsPrefix) {
-		errors = append(errors, fmt.Errorf("%s must contain between 2 and 45 characters. The name can contain only letters, numbers, and hyphens. The name must start with a letter and must end with an alphanumeric character.. Got %q.", k, dnsPrefix))
+	errMsg := fmt.Sprintf("the %q must begin and end with an letter or number, contain only letters, numbers, and hyphens and be between 1 and 54 characters in length, got", k)
+
+	if len(dnsPrefix) < 2 {
+		re := regexp.MustCompile(`^[a-zA-Z\d]`)
+		if re != nil && !re.MatchString(dnsPrefix) {
+			errors = append(errors, fmt.Errorf("%s %q", errMsg, dnsPrefix))
+		}
+	} else {
+		re := regexp.MustCompile(`^[a-zA-Z\d][-a-zA-Z\d]{0,52}[a-zA-Z\d]$`)
+		if re != nil && !re.MatchString(dnsPrefix) {
+			errors = append(errors, fmt.Errorf("%s %q", errMsg, dnsPrefix))
+		}
 	}
 
 	return warnings, errors

internal/services/containers/validate/kubernetes_test.go

@@ -114,13 +114,41 @@ func TestKubernetesDNSPrefix(t *testing.T) {
 			Errors:    1,
 		},
 		{
-			DNSPrefix: "a",
+			DNSPrefix: "aBc-123ab-",
+			Errors:    1,
+		},
+		{
+			DNSPrefix: "-aBc-123abc",
 			Errors:    1,
 		},
+		{
+			DNSPrefix: "a",
+			Errors:    0,
+		},
 		{
 			DNSPrefix: "aBc-123abc",
 			Errors:    0,
 		},
+		{
+			DNSPrefix: "ThisIsAKubernetesDNSPrefixThatIsExactlyFiftyFourCharac",
+			Errors:    0,
+		},
+		{
+			DNSPrefix: "ThisIsAKubernetesDNSPrefixThatIsNotExactlyFiftyFourChar",
+			Errors:    1,
+		},
+		{
+			DNSPrefix: "2",
+			Errors:    0,
+		},
+		{
+			DNSPrefix: "2ndCluster",
+			Errors:    0,
+		},
+		{
+			DNSPrefix: "aBc-123abc2",
+			Errors:    0,
+		},
 	}
 
 	for _, tc := range cases {

website/docs/r/kubernetes_cluster.html.markdown

@@ -71,13 +71,11 @@ The following arguments are supported:
 
 * `default_node_pool` - (Required) A `default_node_pool` block as defined below.
 
-* `dns_prefix` - (Optional) DNS prefix specified when creating the managed cluster. Changing this forces a new resource to be created.
+* `dns_prefix` - (Optional) DNS prefix specified when creating the managed cluster. Possible values must begin and end with an letter or number, contain only letters, numbers, and hyphens and be between 1 and 54 characters in length. Changing this forces a new resource to be created.
 
 * `dns_prefix_private_cluster` - (Optional) Specifies the DNS prefix to use with private clusters. Changing this forces a new resource to be created.
 
--> **Note:** One of `dns_prefix` or `dns_prefix_private_cluster` must be specified.
-
--> **Note:** The `dns_prefix` must contain between 3 and 45 characters, and can contain only letters, numbers, and hyphens. It must start with a letter and must end with a letter or a number.
+-> **Note:** You must define either a `dns_prefix` or a `dns_prefix_private_cluster` field.
 
 In addition, one of either `identity` or `service_principal` blocks must be specified.
 
@@ -219,9 +217,9 @@ resource "azurerm_kubernetes_cluster" "example" {
 
 * `workload_identity_enabled` - (Optional) Specifies whether Azure AD Workload Identity should be enabled for the Cluster. Defaults to `false`.
 
--> **Note** To enable Azure AD Workload Identity `oidc_issuer_enabled` must be set to `true`.
+-> **Note:** To enable Azure AD Workload Identity `oidc_issuer_enabled` must be set to `true`.
 
--> **Note** This requires that the Preview Feature `Microsoft.ContainerService/EnableWorkloadIdentityPreview` is enabled and the Resource Provider is re-registered, see [the documentation](https://learn.microsoft.com/en-us/azure/aks/workload-identity-deploy-cluster#register-the-enableworkloadidentitypreview-feature-flag) for more information.
+-> **Note:** This requires that the Preview Feature `Microsoft.ContainerService/EnableWorkloadIdentityPreview` is enabled and the Resource Provider is re-registered, see [the documentation](https://learn.microsoft.com/en-us/azure/aks/workload-identity-deploy-cluster#register-the-enableworkloadidentitypreview-feature-flag) for more information.
 
 * `public_network_access_enabled` - (Optional) Whether public network access is allowed for this Kubernetes Cluster. Defaults to `true`. Changing this forces a new resource to be created.
 
@@ -470,7 +468,7 @@ An `identity` block supports the following:
 
 * `identity_ids` - (Optional) Specifies a list of User Assigned Managed Identity IDs to be assigned to this Kubernetes Cluster.
 
-~> **NOTE:** This is required when `type` is set to `UserAssigned`.
+~> **Note:** This is required when `type` is set to `UserAssigned`.
 
 ---
 
@@ -488,7 +486,7 @@ A `key_vault_secrets_provider` block supports the following:
 
 * `secret_rotation_interval` - (Optional) The interval to poll for secret rotation. This attribute is only set when `secret_rotation` is true and defaults to `2m`.
 
--> **NOTE:** To enable`key_vault_secrets_provider` either `secret_rotation_enabled` or `secret_rotation_interval` must be specified.
+-> **Note:** To enable`key_vault_secrets_provider` either `secret_rotation_enabled` or `secret_rotation_interval` must be specified.
 
 ---
 
@@ -524,7 +522,7 @@ The `kubelet_identity` block supports the following:
 
 * `user_assigned_identity_id` - (Optional) The ID of the User Assigned Identity assigned to the Kubelets. If not specified a Managed Identity is created automatically. Changing this forces a new resource to be created.
 
--> **NOTE:** When `kubelet_identity` is enabled - The `type` field in the `identity` block must be set to `UserAssigned` and `identity_ids` must be set.
+-> **Note:** When `kubelet_identity` is enabled - The `type` field in the `identity` block must be set to `UserAssigned` and `identity_ids` must be set.
 
 ---
 
@@ -722,7 +720,7 @@ A `storage_profile` block supports the following:
 
 * `disk_driver_version` - (Optional) Disk CSI Driver version to be used. Possible values are `v1` and `v2`. Defaults to `v1`.
 
--> **NOTE:** `Azure Disk CSI driver v2` is currently in [Public Preview](https://azure.microsoft.com/en-us/updates/public-preview-azure-disk-csi-driver-v2-in-aks/) on an opt-in basis. To use it, the feature `EnableAzureDiskCSIDriverV2` for namespace `Microsoft.ContainerService` must be requested.
+-> **Note:** `Azure Disk CSI driver v2` is currently in [Public Preview](https://azure.microsoft.com/en-us/updates/public-preview-azure-disk-csi-driver-v2-in-aks/) on an opt-in basis. To use it, the feature `EnableAzureDiskCSIDriverV2` for namespace `Microsoft.ContainerService` must be requested.
 
 * `file_driver_enabled` - (Optional) Is the File CSI driver enabled? Defaults to `true`.