provider/aws: Add "no_device" support to ephemeral block devices (#10547)

Fixes #8455, #5390

This add a new `no_device` attribute to `ephemeral_block_device` block,
which allows users omit ephemeral devices from AMI's predefined block
device mappings, which is useful for EBS-only instance types.

builtin/providers/aws/resource_aws_instance.go

@@ -268,7 +268,12 @@ func resourceAwsInstance() *schema.Resource {
 
 						"virtual_name": &schema.Schema{
 							Type:     schema.TypeString,
-							Required: true,
+							Optional: true,
+						},
+
+						"no_device": &schema.Schema{
+							Type:     schema.TypeBool,
+							Optional: true,
 						},
 					},
 				},
@@ -277,6 +282,9 @@ func resourceAwsInstance() *schema.Resource {
 					m := v.(map[string]interface{})
 					buf.WriteString(fmt.Sprintf("%s-", m["device_name"].(string)))
 					buf.WriteString(fmt.Sprintf("%s-", m["virtual_name"].(string)))
+					if v, ok := m["no_device"].(bool); ok && v {
+						buf.WriteString(fmt.Sprintf("%t-", v))
+					}
 					return hashcode.String(buf.String())
 				},
 			},
@@ -936,10 +944,21 @@ func readBlockDeviceMappingsFromConfig(
 		vL := v.(*schema.Set).List()
 		for _, v := range vL {
 			bd := v.(map[string]interface{})
-			blockDevices = append(blockDevices, &ec2.BlockDeviceMapping{
+			bdm := &ec2.BlockDeviceMapping{
 				DeviceName:  aws.String(bd["device_name"].(string)),
 				VirtualName: aws.String(bd["virtual_name"].(string)),
-			})
+			}
+			if v, ok := bd["no_device"].(bool); ok && v {
+				bdm.NoDevice = aws.String("")
+				// When NoDevice is true, just ignore VirtualName since it's not needed
+				bdm.VirtualName = nil
+			}
+
+			if bdm.NoDevice == nil && aws.StringValue(bdm.VirtualName) == "" {
+				return nil, fmt.Errorf("virtual_name cannot be empty when no_device is false or undefined.")
+			}
+
+			blockDevices = append(blockDevices, bdm)
 		}
 	}
 

builtin/providers/aws/resource_aws_instance_test.go

@@ -285,6 +285,99 @@ func TestAccAWSInstance_rootInstanceStore(t *testing.T) {
 	})
 }
 
+func TestAcctABSInstance_noAMIEphemeralDevices(t *testing.T) {
+	var v ec2.Instance
+
+	testCheck := func() resource.TestCheckFunc {
+		return func(*terraform.State) error {
+
+			// Map out the block devices by name, which should be unique.
+			blockDevices := make(map[string]*ec2.InstanceBlockDeviceMapping)
+			for _, blockDevice := range v.BlockDeviceMappings {
+				blockDevices[*blockDevice.DeviceName] = blockDevice
+			}
+
+			// Check if the root block device exists.
+			if _, ok := blockDevices["/dev/sda1"]; !ok {
+				return fmt.Errorf("block device doesn't exist: /dev/sda1")
+			}
+
+			// Check if the secondary block not exists.
+			if _, ok := blockDevices["/dev/sdb"]; ok {
+				return fmt.Errorf("block device exist: /dev/sdb")
+			}
+
+			// Check if the third block device not exists.
+			if _, ok := blockDevices["/dev/sdc"]; ok {
+				return fmt.Errorf("block device exist: /dev/sdc")
+			}
+			return nil
+		}
+	}
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:      func() { testAccPreCheck(t) },
+		IDRefreshName: "aws_instance.foo",
+		IDRefreshIgnore: []string{
+			"ephemeral_block_device", "security_groups", "vpc_security_groups"},
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckInstanceDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: `
+					resource "aws_instance" "foo" {
+						# us-west-2
+						ami = "ami-01f05461"  // This AMI (Ubuntu) contains two ephemerals
+
+						instance_type = "c3.large"
+
+						root_block_device {
+							volume_type = "gp2"
+							volume_size = 11
+						}
+						ephemeral_block_device {
+							device_name = "/dev/sdb"
+							no_device = true
+						}
+						ephemeral_block_device {
+							device_name = "/dev/sdc"
+							no_device = true
+						}
+					}`,
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckInstanceExists(
+						"aws_instance.foo", &v),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "ami", "ami-01f05461"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "ebs_optimized", "false"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "instance_type", "c3.large"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "root_block_device.#", "1"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "root_block_device.0.volume_size", "11"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "root_block_device.0.volume_type", "gp2"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "ebs_block_device.#", "0"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "ephemeral_block_device.#", "2"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "ephemeral_block_device.172787947.device_name", "/dev/sdb"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "ephemeral_block_device.172787947.no_device", "true"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "ephemeral_block_device.3336996981.device_name", "/dev/sdc"),
+					resource.TestCheckResourceAttr(
+						"aws_instance.foo", "ephemeral_block_device.3336996981.no_device", "true"),
+					testCheck(),
+				),
+			},
+		},
+	})
+}
+
 func TestAccAWSInstance_sourceDestCheck(t *testing.T) {
 	var v ec2.Instance
 

website/source/docs/providers/aws/r/instance.html.markdown

@@ -126,9 +126,10 @@ Modifying any `ebs_block_device` currently requires resource replacement.
 Each `ephemeral_block_device` supports the following:
 
 * `device_name` - The name of the block device to mount on the instance.
-* `virtual_name` - The [Instance Store Device
+* `virtual_name` - (Optional) The [Instance Store Device
   Name](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/InstanceStorage.html#InstanceStoreDeviceNames)
-  (e.g. `"ephemeral0"`)
+  (e.g. `"ephemeral0"`).
+* `no_device` - (Optional) Suppresses the specified device included in the AMI's block device mapping.
 
 Each AWS Instance type has a different set of Instance Store block devices
 available for attachment. AWS [publishes a