Fix for ER bandwidth reduction issue #3983

Reduction in bandwidth forces new resource, utilizing CustomizeDiff

azurerm/internal/services/network/express_route_circuit_resource.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/Azure/azure-sdk-for-go/services/network/mgmt/2019-09-01/network"
+	"github.com/hashicorp/terraform-plugin-sdk/helper/customdiff"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/schema"
 	"github.com/hashicorp/terraform-plugin-sdk/helper/validation"
 	"github.com/terraform-providers/terraform-provider-azurerm/azurerm/helpers/azure"
@@ -31,6 +32,13 @@ func resourceArmExpressRouteCircuit() *schema.Resource {
 			State: schema.ImportStatePassthrough,
 		},
 
+		CustomizeDiff: customdiff.Sequence(
+			// If bandwidth is reduced force a new resource
+			customdiff.ForceNewIfChange("bandwidth_in_mbps", func(old, new, meta interface{}) bool {
+				return new.(int) < old.(int)
+			}),
+		),
+
 		Timeouts: &schema.ResourceTimeout{
 			Create: schema.DefaultTimeout(30 * time.Minute),
 			Read:   schema.DefaultTimeout(5 * time.Minute),

azurerm/internal/services/network/tests/express_route_circuit_resource_test.go

@@ -28,6 +28,7 @@ func TestAccAzureRMExpressRouteCircuit(t *testing.T) {
 			"allowClassicOperationsUpdate": testAccAzureRMExpressRouteCircuit_allowClassicOperationsUpdate,
 			"requiresImport":               testAccAzureRMExpressRouteCircuit_requiresImport,
 			"data_basic":                   testAccDataSourceAzureRMExpressRoute_basicMetered,
+			"bandwidthReduction":           testAccAzureRMExpressRouteCircuit_bandwidthReduction,
 		},
 		"PrivatePeering": {
 			"azurePrivatePeering":           testAccAzureRMExpressRouteCircuitPeering_azurePrivatePeering,
@@ -273,6 +274,33 @@ func testAccAzureRMExpressRouteCircuit_allowClassicOperationsUpdate(t *testing.T
 	})
 }
 
+func testAccAzureRMExpressRouteCircuit_bandwidthReduction(t *testing.T) {
+	data := acceptance.BuildTestData(t, "azurerm_express_route_circuit", "test")
+	var erc network.ExpressRouteCircuit
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { acceptance.PreCheck(t) },
+		Providers:    acceptance.SupportedProviders,
+		CheckDestroy: testCheckAzureRMExpressRouteCircuitDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAzureRMExpressRouteCircuit_bandwidthReductionConfig(data, "100"),
+				Check: resource.ComposeTestCheckFunc(
+					testCheckAzureRMExpressRouteCircuitExists("azurerm_express_route_circuit.test", &erc),
+					resource.TestCheckResourceAttr(data.ResourceName, "bandwidth_in_mbps", "100"),
+				),
+			},
+			{
+				Config: testAccAzureRMExpressRouteCircuit_bandwidthReductionConfig(data, "50"),
+				Check: resource.ComposeTestCheckFunc(
+					testCheckAzureRMExpressRouteCircuitExists("azurerm_express_route_circuit.test", &erc),
+					resource.TestCheckResourceAttr(data.ResourceName, "bandwidth_in_mbps", "50"),
+				),
+			},
+		},
+	})
+}
+
 func testCheckAzureRMExpressRouteCircuitExists(resourceName string, erc *network.ExpressRouteCircuit) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
 		rs, ok := s.RootModule().Resources[resourceName]
@@ -528,3 +556,37 @@ resource "azurerm_express_route_circuit" "test" {
 }
 `, data.RandomInteger, data.Locations.Primary, data.RandomInteger, allowClassicOperations)
 }
+
+func testAccAzureRMExpressRouteCircuit_bandwidthReductionConfig(data acceptance.TestData, bandwidth string) string {
+	return fmt.Sprintf(`
+provider "azurerm" {
+  features {}
+}
+
+resource "azurerm_resource_group" "test" {
+  name     = "acctestRG-%d"
+  location = "%s"
+}
+
+resource "azurerm_express_route_circuit" "test" {
+  name                  = "acctest-erc-%d"
+  location              = azurerm_resource_group.test.location
+  resource_group_name   = azurerm_resource_group.test.name
+  service_provider_name = "Equinix"
+  peering_location      = "Silicon Valley"
+  bandwidth_in_mbps     = %s
+
+  sku {
+    tier   = "Standard"
+    family = "MeteredData"
+  }
+
+  allow_classic_operations = false
+
+  tags = {
+    Environment = "production"
+    Purpose     = "AcceptanceTests"
+  }
+}
+`, data.RandomInteger, data.Locations.Primary, data.RandomInteger, bandwidth)
+}

vendor/modules.txt

@@ -246,6 +246,7 @@ github.com/hashicorp/logutils
 github.com/hashicorp/terraform-config-inspect/tfconfig
 # github.com/hashicorp/terraform-plugin-sdk v1.6.0
 github.com/hashicorp/terraform-plugin-sdk/helper/acctest
+github.com/hashicorp/terraform-plugin-sdk/helper/customdiff
 github.com/hashicorp/terraform-plugin-sdk/helper/hashcode
 github.com/hashicorp/terraform-plugin-sdk/helper/logging
 github.com/hashicorp/terraform-plugin-sdk/helper/mutexkv