resource/aws_docdb_cluster: Allow adding/modifying serverless_v2_scaling_configuration without replacement

.changelog/45049.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_docdb_cluster: Allow adding and modifying `serverless_v2_scaling_configuration` without forcing cluster replacement
+```

internal/service/docdb/cluster.go

@@ -17,7 +17,6 @@ import (
 	"github.com/hashicorp/aws-sdk-go-base/v2/tfawserr"
 	"github.com/hashicorp/go-cty/cty"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
-	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/customdiff"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/retry"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/validation"
@@ -303,9 +302,10 @@ func resourceCluster() *schema.Resource {
 				},
 			},
 			"serverless_v2_scaling_configuration": {
-				Type:     schema.TypeList,
-				Optional: true,
-				MaxItems: 1,
+				Type:             schema.TypeList,
+				Optional:         true,
+				MaxItems:         1,
+				DiffSuppressFunc: verify.SuppressMissingOptionalConfigurationBlock,
 				Elem: &schema.Resource{
 					Schema: map[string]*schema.Schema{
 						names.AttrMaxCapacity: {
@@ -315,6 +315,15 @@ func resourceCluster() *schema.Resource {
 								validation.FloatBetween(1.0, 256.0),
 								validateServerlessCapacity,
 							),
+							DiffSuppressFunc: func(k, old, new string, d *schema.ResourceData) bool {
+								config := d.GetRawConfig()
+								raw := config.GetAttr("serverless_v2_scaling_configuration")
+
+								if raw.LengthInt() == 0 && (old != "0" && old != "") && (new == "0" || new == "") {
+									return true
+								}
+								return false
+							},
 						},
 						"min_capacity": {
 							Type:     schema.TypeFloat,
@@ -323,6 +332,15 @@ func resourceCluster() *schema.Resource {
 								validation.FloatBetween(0.5, 256.0),
 								validateServerlessCapacity,
 							),
+							DiffSuppressFunc: func(k, old, new string, d *schema.ResourceData) bool {
+								config := d.GetRawConfig()
+								raw := config.GetAttr("serverless_v2_scaling_configuration")
+
+								if raw.LengthInt() == 0 && (old != "0" && old != "") && (new == "0" || new == "") {
+									return true
+								}
+								return false
+							},
 						},
 					},
 				},
@@ -372,18 +390,6 @@ func resourceCluster() *schema.Resource {
 				Elem:     &schema.Schema{Type: schema.TypeString},
 			},
 		},
-		CustomizeDiff: customdiff.All(
-			// if serverless_v2_scaling_configuration is newly set or deleted, ForceNew is required
-			customdiff.ForceNewIfChange("serverless_v2_scaling_configuration",
-				func(_ context.Context, old, new, meta any) bool {
-					o := old != nil && len(old.([]any)) > 0
-					n := new != nil && len(new.([]any)) > 0
-					if (o && n) || (!o && !n) {
-						return false
-					}
-					return true
-				}),
-		),
 	}
 }
 

internal/service/docdb/cluster_test.go

@@ -1085,17 +1085,76 @@ func TestAccDocDBCluster_serverless(t *testing.T) {
 				),
 			},
 			{
+				// Remove serverless config from Terraform code
+				// DiffSuppressFunc should prevent drift warning
 				Config: testAccClusterConfig_serverlessRemoved(rName),
 				ConfigPlanChecks: resource.ConfigPlanChecks{
 					PreApply: []plancheck.PlanCheck{
-						plancheck.ExpectResourceAction(resourceName, plancheck.ResourceActionDestroyBeforeCreate),
+						plancheck.ExpectResourceAction(resourceName, plancheck.ResourceActionNoop),
+					},
+				},
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckClusterExists(ctx, resourceName, &dbCluster),
+					// AWS still has the serverless config, and DiffSuppressFunc accepts it
+					resource.TestCheckResourceAttr(resourceName, "serverless_v2_scaling_configuration.#", "1"),
+					resource.TestCheckResourceAttr(resourceName, "serverless_v2_scaling_configuration.0.min_capacity", "1"),
+					resource.TestCheckResourceAttr(resourceName, "serverless_v2_scaling_configuration.0.max_capacity", "1.5"),
+				),
+			},
+		},
+	})
+}
+
+func TestAccDocDBCluster_serverlessAddToExisting(t *testing.T) {
+	ctx := acctest.Context(t)
+	var dbCluster awstypes.DBCluster
+	rName := sdkacctest.RandomWithPrefix(acctest.ResourcePrefix)
+	resourceName := "aws_docdb_cluster.test"
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:                 func() { acctest.PreCheck(ctx, t) },
+		ErrorCheck:               acctest.ErrorCheck(t, names.DocDBServiceID),
+		ProtoV5ProviderFactories: acctest.ProtoV5ProviderFactories,
+		CheckDestroy:             testAccCheckClusterDestroy(ctx),
+		Steps: []resource.TestStep{
+			{
+				Config: testAccClusterConfig_serverlessRemoved(rName),
+				ConfigPlanChecks: resource.ConfigPlanChecks{
+					PreApply: []plancheck.PlanCheck{
+						plancheck.ExpectResourceAction(resourceName, plancheck.ResourceActionCreate),
 					},
 				},
 				Check: resource.ComposeTestCheckFunc(
 					testAccCheckClusterExists(ctx, resourceName, &dbCluster),
 					resource.TestCheckResourceAttr(resourceName, "serverless_v2_scaling_configuration.#", "0"),
 				),
 			},
+			{
+				ResourceName:      resourceName,
+				ImportState:       true,
+				ImportStateVerify: true,
+				ImportStateVerifyIgnore: []string{
+					names.AttrAllowMajorVersionUpgrade,
+					names.AttrApplyImmediately,
+					names.AttrFinalSnapshotIdentifier,
+					"master_password",
+					"skip_final_snapshot",
+				},
+			},
+			{
+				Config: testAccClusterConfig_serverless(rName, 0.5, 4.0),
+				ConfigPlanChecks: resource.ConfigPlanChecks{
+					PreApply: []plancheck.PlanCheck{
+						plancheck.ExpectResourceAction(resourceName, plancheck.ResourceActionUpdate),
+					},
+				},
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckClusterExists(ctx, resourceName, &dbCluster),
+					resource.TestCheckResourceAttr(resourceName, "serverless_v2_scaling_configuration.#", "1"),
+					resource.TestCheckResourceAttr(resourceName, "serverless_v2_scaling_configuration.0.min_capacity", "0.5"),
+					resource.TestCheckResourceAttr(resourceName, "serverless_v2_scaling_configuration.0.max_capacity", "4"),
+				),
+			},
 		},
 	})
 }

website/docs/r/docdb_cluster.html.markdown

@@ -100,7 +100,8 @@ The `restore_to_point_in_time` block supports the following arguments:
 ### Serverless V2 Scaling Configuration
 
 The `serverless_v2_scaling_configuration` block supports the following arguments.
-Adding this block (i.e. switching to serverless) or removing it (i.e. switching from serverless) will trigger cluster replacement.
+
+~> **NOTE:** Once configured, the serverless scaling configuration cannot be removed without recreating the cluster. If the configuration block is removed from Terraform, the configuration values will remain and continue to be active.
 
 * `max_capacity` - (Required) Maximum number of Amazon DocumentDB capacity units (DCUs) for an instance in an Amazon DocumentDB Serverless cluster. Valid values are multiples of 0.5 between 1 and 256.
 * `min_capacity` - (Required) Minimum number of Amazon DocumentDB capacity units (DCUs) for an instance in an Amazon DocumentDB Serverless cluster. Valid values are multiples of 0.5 between 0.5 and 256.