enable no_ephemeral for spot devices, clean up ranging behavior, update docs

builder/amazon/common/step_run_source_instance.go

@@ -127,10 +127,9 @@ func (s *StepRunSourceInstance) Run(ctx context.Context, state multistep.StateBa
 		// don't clutter up console views and cause confusion.
 		log.Printf("no_ephemeral was set, so creating drives xvdca-xvdcz as empty mappings")
 		DefaultEphemeralDeviceLetters := "abcdefghijklmnopqrstuvwxyz"
-		for i := 0; i < len(DefaultEphemeralDeviceLetters); i++ {
-
+		for _, letter := range DefaultEphemeralDeviceLetters {
 			bd := &ec2.BlockDeviceMapping{
-				DeviceName: aws.String("xvdc" + string(DefaultEphemeralDeviceLetters[i])),
+				DeviceName: aws.String("xvdc" + string(letter)),
 				NoDevice:   aws.String(""),
 			}
 			runOpts.BlockDeviceMappings = append(runOpts.BlockDeviceMappings, bd)

builder/amazon/common/step_run_spot_instance.go

@@ -41,12 +41,32 @@ type StepRunSpotInstance struct {
 	UserData                          string
 	UserDataFile                      string
 	Ctx                               interpolate.Context
+	NoEphemeral                       bool
 
 	instanceId string
 }
 
 func (s *StepRunSpotInstance) CreateTemplateData(userData *string, az string,
 	state multistep.StateBag, marketOptions *ec2.LaunchTemplateInstanceMarketOptionsRequest) *ec2.RequestLaunchTemplateData {
+	blockDeviceMappings := s.LaunchMappings.BuildEC2BlockDeviceMappings()
+	if s.NoEphemeral {
+		// This is only relevant for windows guests. Ephemeral drives by
+		// default are assigned to drive names xvdca-xvdcz.
+		// When vms are launched from the AWS console, they're automatically
+		// removed from the block devices if the user hasn't said to use them,
+		// but the SDK does not perform this cleanup. The following code just
+		// manually removes the ephemeral drives from the mapping so that they
+		// don't clutter up console views and cause confusion.
+		log.Printf("no_ephemeral was set, so creating drives xvdca-xvdcz as empty mappings")
+		DefaultEphemeralDeviceLetters := "abcdefghijklmnopqrstuvwxyz"
+		for _, letter := range DefaultEphemeralDeviceLetters {
+			bd := &ec2.BlockDeviceMapping{
+				DeviceName: aws.String("xvdc" + string(letter)),
+				NoDevice:   aws.String(""),
+			}
+			blockDeviceMappings = append(blockDeviceMappings, bd)
+		}
+	}
 	// Convert the BlockDeviceMapping into a
 	// LaunchTemplateBlockDeviceMappingRequest. These structs are identical,
 	// except for the EBS field -- on one, that field contains a
@@ -55,7 +75,6 @@ func (s *StepRunSpotInstance) CreateTemplateData(userData *string, az string,
 	// LaunchTemplateEbsBlockDeviceRequest structs are themselves
 	// identical except for the struct's name, so you can cast one directly
 	// into the other.
-	blockDeviceMappings := s.LaunchMappings.BuildEC2BlockDeviceMappings()
 	var launchMappingRequests []*ec2.LaunchTemplateBlockDeviceMappingRequest
 	for _, mapping := range blockDeviceMappings {
 		launchRequest := &ec2.LaunchTemplateBlockDeviceMappingRequest{

builder/amazon/ebs/builder.go

@@ -53,11 +53,15 @@ type Config struct {
 	// engine](/docs/templates/engine.html), see [Build template
 	// data](#build-template-data) for more information.
 	VolumeRunTags awscommon.TagMap `mapstructure:"run_volume_tags"`
-	// If you set this flag, we'll add clauses to the
-	// launch_block_device_mappings that make sure ephemeral drives don't show
-	// up in the EC2 console. If you launched from the EC2 console, you'd get
-	// this automatically, but the SDK does not provide this service.
-	// This only applies when you are not running spot instances.
+	// Relevant only to Windows guests: If you set this flag, we'll add clauses
+	// to the launch_block_device_mappings that make sure ephemeral drives
+	// don't show up in the EC2 console. If you launched from the EC2 console,
+	// you'd get this automatically, but the SDK does not provide this service.
+	// For more information, see
+	// https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/InstanceStorage.html.
+	// Because we don't validate the OS type of your guest, it is up to you to
+	// make sure you don't set this for *nix guests; behavior may be
+	// unpredictable.
 	NoEphemeral bool `mapstructure:"no_ephemeral" required:"false"`
 
 	ctx interpolate.Context

website/source/partials/builder/amazon/ebs/_Config-not-required.html.md

@@ -22,9 +22,13 @@
     engine](/docs/templates/engine.html), see [Build template
     data](#build-template-data) for more information.
     
--   `no_ephemeral` (bool) - If you set this flag, we'll add clauses to the
-    launch_block_device_mappings that make sure ephemeral drives don't show
-    up in the EC2 console. If you launched from the EC2 console, you'd get
-    this automatically, but the SDK does not provide this service.
-    This only applies when you are not running spot instances.
+-   `no_ephemeral` (bool) - Relevant only to Windows guests: If you set this flag, we'll add clauses
+    to the launch_block_device_mappings that make sure ephemeral drives
+    don't show up in the EC2 console. If you launched from the EC2 console,
+    you'd get this automatically, but the SDK does not provide this service.
+    For more information, see
+    https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/InstanceStorage.html.
+    Because we don't validate the OS type of your guest, it is up to you to
+    make sure you don't set this for *nix guests; behavior may be
+    unpredictable.