resource/aws_rds_cluster: Properly update master_password during snapshot restore

aws/resource_aws_rds_cluster.go

@@ -489,6 +489,11 @@ func resourceAwsRDSClusterCreate(d *schema.ResourceData, meta interface{}) error
 			opts.KmsKeyId = aws.String(attr.(string))
 		}
 
+		if attr, ok := d.GetOk("master_password"); ok {
+			modifyDbClusterInput.MasterUserPassword = aws.String(attr.(string))
+			requiresModifyDbCluster = true
+		}
+
 		if attr, ok := d.GetOk("option_group_name"); ok {
 			opts.OptionGroupName = aws.String(attr.(string))
 		}

aws/resource_aws_rds_cluster_test.go

@@ -1353,6 +1353,86 @@ func TestAccAWSRDSCluster_SnapshotIdentifier_EngineVersion_Equal(t *testing.T) {
 	})
 }
 
+func TestAccAWSRDSCluster_SnapshotIdentifier_MasterPassword(t *testing.T) {
+	var dbCluster, sourceDbCluster rds.DBCluster
+	var dbClusterSnapshot rds.DBClusterSnapshot
+
+	rName := acctest.RandomWithPrefix("tf-acc-test")
+	sourceDbResourceName := "aws_rds_cluster.source"
+	snapshotResourceName := "aws_db_cluster_snapshot.test"
+	resourceName := "aws_rds_cluster.test"
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckAWSDBInstanceDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSRDSClusterConfig_SnapshotIdentifier_MasterPassword(rName, "password1"),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSClusterExists(sourceDbResourceName, &sourceDbCluster),
+					testAccCheckDbClusterSnapshotExists(snapshotResourceName, &dbClusterSnapshot),
+					testAccCheckAWSClusterExists(resourceName, &dbCluster),
+					resource.TestCheckResourceAttr(resourceName, "master_password", "password1"),
+				),
+			},
+			{
+				ResourceName:      resourceName,
+				ImportState:       true,
+				ImportStateVerify: true,
+				ImportStateVerifyIgnore: []string{
+					"apply_immediately",
+					"cluster_identifier_prefix",
+					"master_password",
+					"skip_final_snapshot",
+					"snapshot_identifier",
+				},
+			},
+		},
+	})
+}
+
+func TestAccAWSRDSCluster_SnapshotIdentifier_MasterUsername(t *testing.T) {
+	var dbCluster, sourceDbCluster rds.DBCluster
+	var dbClusterSnapshot rds.DBClusterSnapshot
+
+	rName := acctest.RandomWithPrefix("tf-acc-test")
+	sourceDbResourceName := "aws_rds_cluster.source"
+	snapshotResourceName := "aws_db_cluster_snapshot.test"
+	resourceName := "aws_rds_cluster.test"
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckAWSDBInstanceDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSRDSClusterConfig_SnapshotIdentifier_MasterUsername(rName, "username1"),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSClusterExists(sourceDbResourceName, &sourceDbCluster),
+					testAccCheckDbClusterSnapshotExists(snapshotResourceName, &dbClusterSnapshot),
+					testAccCheckAWSClusterExists(resourceName, &dbCluster),
+					resource.TestCheckResourceAttr(resourceName, "master_username", "foo"),
+				),
+				// It is not currently possible to update the master username in the RDS API
+				ExpectNonEmptyPlan: true,
+			},
+			{
+				ResourceName:      resourceName,
+				ImportState:       true,
+				ImportStateVerify: true,
+				ImportStateVerifyIgnore: []string{
+					"apply_immediately",
+					"cluster_identifier_prefix",
+					"master_password",
+					"skip_final_snapshot",
+					"snapshot_identifier",
+				},
+			},
+		},
+	})
+}
+
 func TestAccAWSRDSCluster_SnapshotIdentifier_PreferredBackupWindow(t *testing.T) {
 	var dbCluster, sourceDbCluster rds.DBCluster
 	var dbClusterSnapshot rds.DBClusterSnapshot
@@ -2651,6 +2731,52 @@ resource "aws_rds_cluster" "test" {
 `, rName, engine, engineVersionSource, rName, rName, engine, engineVersion)
 }
 
+func testAccAWSRDSClusterConfig_SnapshotIdentifier_MasterPassword(rName, masterPassword string) string {
+	return fmt.Sprintf(`
+resource "aws_rds_cluster" "source" {
+  cluster_identifier  = "%[1]s-source"
+  master_password     = "barbarbarbar"
+  master_username     = "foo"
+  skip_final_snapshot = true
+}
+
+resource "aws_db_cluster_snapshot" "test" {
+  db_cluster_identifier          = "${aws_rds_cluster.source.id}"
+  db_cluster_snapshot_identifier = %[1]q
+}
+
+resource "aws_rds_cluster" "test" {
+  cluster_identifier      = %[1]q
+  master_password         = %[2]q
+  skip_final_snapshot     = true
+  snapshot_identifier     = "${aws_db_cluster_snapshot.test.id}"
+}
+`, rName, masterPassword)
+}
+
+func testAccAWSRDSClusterConfig_SnapshotIdentifier_MasterUsername(rName, masterUsername string) string {
+	return fmt.Sprintf(`
+resource "aws_rds_cluster" "source" {
+  cluster_identifier  = "%[1]s-source"
+  master_password     = "barbarbarbar"
+  master_username     = "foo"
+  skip_final_snapshot = true
+}
+
+resource "aws_db_cluster_snapshot" "test" {
+  db_cluster_identifier          = "${aws_rds_cluster.source.id}"
+  db_cluster_snapshot_identifier = %[1]q
+}
+
+resource "aws_rds_cluster" "test" {
+  cluster_identifier      = %[1]q
+  master_username         = %[2]q
+  skip_final_snapshot     = true
+  snapshot_identifier     = "${aws_db_cluster_snapshot.test.id}"
+}
+`, rName, masterUsername)
+}
+
 func testAccAWSRDSClusterConfig_SnapshotIdentifier_PreferredBackupWindow(rName, preferredBackupWindow string) string {
 	return fmt.Sprintf(`
 resource "aws_rds_cluster" "source" {

website/docs/r/rds_cluster.html.markdown

@@ -89,7 +89,7 @@ The following arguments are supported:
 * `deletion_protection` - (Optional) If the DB instance should have deletion protection enabled. The database can't be deleted when this value is set to `true`. The default is `false`.
 * `master_password` - (Required unless a `snapshot_identifier` or `global_cluster_identifier` is provided) Password for the master DB user. Note that this may
     show up in logs, and it will be stored in the state file. Please refer to the [RDS Naming Constraints][5]
-* `master_username` - (Required unless a `snapshot_identifier` or `global_cluster_identifier` is provided) Username for the master DB user. Please refer to the [RDS Naming Constraints][5]
+* `master_username` - (Required unless a `snapshot_identifier` or `global_cluster_identifier` is provided) Username for the master DB user. Please refer to the [RDS Naming Constraints][5]. This argument does not support in-place updates and cannot be changed during a restore from snapshot.
 * `final_snapshot_identifier` - (Optional) The name of your final DB snapshot
     when this DB cluster is deleted. If omitted, no final snapshot will be
     made.