provider/aws: Support Attachment of ALB Target Groups to Autoscaling Groups (#12855)

Fixes: #12563

```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAwsAutoscalingAttachment_'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/03/18 21:04:31 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAwsAutoscalingAttachment_ -timeout 120m
=== RUN   TestAccAwsAutoscalingAttachment_elb
--- PASS: TestAccAwsAutoscalingAttachment_elb (168.21s)
=== RUN   TestAccAwsAutoscalingAttachment_albTargetGroup
--- PASS: TestAccAwsAutoscalingAttachment_albTargetGroup (363.10s)
PASS
ok  	github.com/hashicorp/terraform/builtin/providers/aws	531.334s
```

builtin/providers/aws/resource_aws_autoscaling_attachment.go

@@ -18,16 +18,22 @@ func resourceAwsAutoscalingAttachment() *schema.Resource {
 		Delete: resourceAwsAutoscalingAttachmentDelete,
 
 		Schema: map[string]*schema.Schema{
-			"autoscaling_group_name": &schema.Schema{
+			"autoscaling_group_name": {
 				Type:     schema.TypeString,
 				ForceNew: true,
 				Required: true,
 			},
 
-			"elb": &schema.Schema{
+			"elb": {
 				Type:     schema.TypeString,
 				ForceNew: true,
-				Required: true,
+				Optional: true,
+			},
+
+			"alb_target_group_arn": {
+				Type:     schema.TypeString,
+				ForceNew: true,
+				Optional: true,
 			},
 		},
 	}
@@ -36,17 +42,31 @@ func resourceAwsAutoscalingAttachment() *schema.Resource {
 func resourceAwsAutoscalingAttachmentCreate(d *schema.ResourceData, meta interface{}) error {
 	asgconn := meta.(*AWSClient).autoscalingconn
 	asgName := d.Get("autoscaling_group_name").(string)
-	elbName := d.Get("elb").(string)
 
-	attachElbInput := &autoscaling.AttachLoadBalancersInput{
+	if v, ok := d.GetOk("elb"); ok {
+		attachOpts := &autoscaling.AttachLoadBalancersInput{
 			AutoScalingGroupName: aws.String(asgName),
-		LoadBalancerNames:    []*string{aws.String(elbName)},
+			LoadBalancerNames:    []*string{aws.String(v.(string))},
 		}
 
-	log.Printf("[INFO] registering asg %s with ELBs %s", asgName, elbName)
+		log.Printf("[INFO] registering asg %s with ELBs %s", asgName, v.(string))
 
-	if _, err := asgconn.AttachLoadBalancers(attachElbInput); err != nil {
+		if _, err := asgconn.AttachLoadBalancers(attachOpts); err != nil {
-		return errwrap.Wrapf(fmt.Sprintf("Failure attaching AutoScaling Group %s with Elastic Load Balancer: %s: {{err}}", asgName, elbName), err)
+			return errwrap.Wrapf(fmt.Sprintf("Failure attaching AutoScaling Group %s with Elastic Load Balancer: %s: {{err}}", asgName, v.(string)), err)
+		}
+	}
+
+	if v, ok := d.GetOk("alb_target_group_arn"); ok {
+		attachOpts := &autoscaling.AttachLoadBalancerTargetGroupsInput{
+			AutoScalingGroupName: aws.String(asgName),
+			TargetGroupARNs:      []*string{aws.String(v.(string))},
+		}
+
+		log.Printf("[INFO] registering asg %s with ALB Target Group %s", asgName, v.(string))
+
+		if _, err := asgconn.AttachLoadBalancerTargetGroups(attachOpts); err != nil {
+			return errwrap.Wrapf(fmt.Sprintf("Failure attaching AutoScaling Group %s with ALB Target Group: %s: {{err}}", asgName, v.(string)), err)
+		}
 	}
 
 	d.SetId(resource.PrefixedUniqueId(fmt.Sprintf("%s-", asgName)))
@@ -57,7 +77,6 @@ func resourceAwsAutoscalingAttachmentCreate(d *schema.ResourceData, meta interfa
 func resourceAwsAutoscalingAttachmentRead(d *schema.ResourceData, meta interface{}) error {
 	asgconn := meta.(*AWSClient).autoscalingconn
 	asgName := d.Get("autoscaling_group_name").(string)
-	elbName := d.Get("elb").(string)
 
 	// Retrieve the ASG properites to get list of associated ELBs
 	asg, err := getAwsAutoscalingGroup(asgName, asgconn)
@@ -71,19 +90,37 @@ func resourceAwsAutoscalingAttachmentRead(d *schema.ResourceData, meta interface
 		return nil
 	}
 
+	if v, ok := d.GetOk("elb"); ok {
 		found := false
 		for _, i := range asg.LoadBalancerNames {
-		if elbName == *i {
+			if v.(string) == *i {
-			d.Set("elb", elbName)
+				d.Set("elb", v.(string))
 				found = true
 				break
 			}
 		}
 
 		if !found {
-		log.Printf("[WARN] Association for %s was not found in ASG assocation", elbName)
+			log.Printf("[WARN] Association for %s was not found in ASG assocation", v.(string))
 			d.SetId("")
 		}
+	}
+
+	if v, ok := d.GetOk("alb_target_group_arn"); ok {
+		found := false
+		for _, i := range asg.TargetGroupARNs {
+			if v.(string) == *i {
+				d.Set("alb_target_group_arn", v.(string))
+				found = true
+				break
+			}
+		}
+
+		if !found {
+			log.Printf("[WARN] Association for %s was not found in ASG assocation", v.(string))
+			d.SetId("")
+		}
+	}
 
 	return nil
 }
@@ -91,17 +128,29 @@ func resourceAwsAutoscalingAttachmentRead(d *schema.ResourceData, meta interface
 func resourceAwsAutoscalingAttachmentDelete(d *schema.ResourceData, meta interface{}) error {
 	asgconn := meta.(*AWSClient).autoscalingconn
 	asgName := d.Get("autoscaling_group_name").(string)
-	elbName := d.Get("elb").(string)
-
-	log.Printf("[INFO] Deleting ELB %s association from: %s", elbName, asgName)
 
+	if v, ok := d.GetOk("elb"); ok {
 		detachOpts := &autoscaling.DetachLoadBalancersInput{
 			AutoScalingGroupName: aws.String(asgName),
-		LoadBalancerNames:    []*string{aws.String(elbName)},
+			LoadBalancerNames:    []*string{aws.String(v.(string))},
 		}
 
+		log.Printf("[INFO] Deleting ELB %s association from: %s", v.(string), asgName)
 		if _, err := asgconn.DetachLoadBalancers(detachOpts); err != nil {
-		return errwrap.Wrapf(fmt.Sprintf("Failure detaching AutoScaling Group %s with Elastic Load Balancer: %s: {{err}}", asgName, elbName), err)
+			return errwrap.Wrapf(fmt.Sprintf("Failure detaching AutoScaling Group %s with Elastic Load Balancer: %s: {{err}}", asgName, v.(string)), err)
+		}
+	}
+
+	if v, ok := d.GetOk("alb_target_group_arn"); ok {
+		detachOpts := &autoscaling.DetachLoadBalancerTargetGroupsInput{
+			AutoScalingGroupName: aws.String(asgName),
+			TargetGroupARNs:      []*string{aws.String(v.(string))},
+		}
+
+		log.Printf("[INFO] Deleting ALB Target Group %s association from: %s", v.(string), asgName)
+		if _, err := asgconn.DetachLoadBalancerTargetGroups(detachOpts); err != nil {
+			return errwrap.Wrapf(fmt.Sprintf("Failure detaching AutoScaling Group %s with ALB Target Group: %s: {{err}}", asgName, v.(string)), err)
+		}
 	}
 
 	return nil

builtin/providers/aws/resource_aws_autoscaling_attachment_test.go

@@ -11,7 +11,7 @@ import (
 	"github.com/hashicorp/terraform/terraform"
 )
 
-func TestAccAwsAutoscalingAttachment_basic(t *testing.T) {
+func TestAccAwsAutoscalingAttachment_elb(t *testing.T) {
 
 	rInt := acctest.RandInt()
 
@@ -19,45 +19,83 @@ func TestAccAwsAutoscalingAttachment_basic(t *testing.T) {
 		PreCheck:  func() { testAccPreCheck(t) },
 		Providers: testAccProviders,
 		Steps: []resource.TestStep{
-			resource.TestStep{
+			{
-				Config: testAccAWSAutoscalingAttachment_basic(rInt),
+				Config: testAccAWSAutoscalingAttachment_elb(rInt),
 				Check: resource.ComposeTestCheckFunc(
-					testAccCheckAWSAutocalingAttachmentExists("aws_autoscaling_group.asg", 0),
+					testAccCheckAWSAutocalingElbAttachmentExists("aws_autoscaling_group.asg", 0),
 				),
 			},
-			// Add in one association
+			{
-			resource.TestStep{
+				Config: testAccAWSAutoscalingAttachment_elb_associated(rInt),
-				Config: testAccAWSAutoscalingAttachment_associated(rInt),
 				Check: resource.ComposeTestCheckFunc(
-					testAccCheckAWSAutocalingAttachmentExists("aws_autoscaling_group.asg", 1),
+					testAccCheckAWSAutocalingElbAttachmentExists("aws_autoscaling_group.asg", 1),
 				),
 			},
-			// Test adding a 2nd
+			{
-			resource.TestStep{
+				Config: testAccAWSAutoscalingAttachment_elb_double_associated(rInt),
-				Config: testAccAWSAutoscalingAttachment_double_associated(rInt),
 				Check: resource.ComposeTestCheckFunc(
-					testAccCheckAWSAutocalingAttachmentExists("aws_autoscaling_group.asg", 2),
+					testAccCheckAWSAutocalingElbAttachmentExists("aws_autoscaling_group.asg", 2),
 				),
 			},
-			// Now remove that newest one
+			{
-			resource.TestStep{
+				Config: testAccAWSAutoscalingAttachment_elb_associated(rInt),
-				Config: testAccAWSAutoscalingAttachment_associated(rInt),
 				Check: resource.ComposeTestCheckFunc(
-					testAccCheckAWSAutocalingAttachmentExists("aws_autoscaling_group.asg", 1),
+					testAccCheckAWSAutocalingElbAttachmentExists("aws_autoscaling_group.asg", 1),
 				),
 			},
-			// Now remove them both
+			{
-			resource.TestStep{
+				Config: testAccAWSAutoscalingAttachment_elb(rInt),
-				Config: testAccAWSAutoscalingAttachment_basic(rInt),
 				Check: resource.ComposeTestCheckFunc(
-					testAccCheckAWSAutocalingAttachmentExists("aws_autoscaling_group.asg", 0),
+					testAccCheckAWSAutocalingElbAttachmentExists("aws_autoscaling_group.asg", 0),
 				),
 			},
 		},
 	})
 }
 
-func testAccCheckAWSAutocalingAttachmentExists(asgname string, loadBalancerCount int) resource.TestCheckFunc {
+func TestAccAwsAutoscalingAttachment_albTargetGroup(t *testing.T) {
+
+	rInt := acctest.RandInt()
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:  func() { testAccPreCheck(t) },
+		Providers: testAccProviders,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccAWSAutoscalingAttachment_alb(rInt),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSAutocalingAlbAttachmentExists("aws_autoscaling_group.asg", 0),
+				),
+			},
+			{
+				Config: testAccAWSAutoscalingAttachment_alb_associated(rInt),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSAutocalingAlbAttachmentExists("aws_autoscaling_group.asg", 1),
+				),
+			},
+			{
+				Config: testAccAWSAutoscalingAttachment_alb_double_associated(rInt),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSAutocalingAlbAttachmentExists("aws_autoscaling_group.asg", 2),
+				),
+			},
+			{
+				Config: testAccAWSAutoscalingAttachment_alb_associated(rInt),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSAutocalingAlbAttachmentExists("aws_autoscaling_group.asg", 1),
+				),
+			},
+			{
+				Config: testAccAWSAutoscalingAttachment_alb(rInt),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckAWSAutocalingAlbAttachmentExists("aws_autoscaling_group.asg", 0),
+				),
+			},
+		},
+	})
+}
+
+func testAccCheckAWSAutocalingElbAttachmentExists(asgname string, loadBalancerCount int) resource.TestCheckFunc {
 	return func(s *terraform.State) error {
 		rs, ok := s.RootModule().Resources[asgname]
 		if !ok {
@@ -83,7 +121,126 @@ func testAccCheckAWSAutocalingAttachmentExists(asgname string, loadBalancerCount
 	}
 }
 
-func testAccAWSAutoscalingAttachment_basic(rInt int) string {
+func testAccCheckAWSAutocalingAlbAttachmentExists(asgname string, targetGroupCount int) resource.TestCheckFunc {
+	return func(s *terraform.State) error {
+		rs, ok := s.RootModule().Resources[asgname]
+		if !ok {
+			return fmt.Errorf("Not found: %s", asgname)
+		}
+
+		conn := testAccProvider.Meta().(*AWSClient).autoscalingconn
+		asg := rs.Primary.ID
+
+		actual, err := conn.DescribeAutoScalingGroups(&autoscaling.DescribeAutoScalingGroupsInput{
+			AutoScalingGroupNames: []*string{aws.String(asg)},
+		})
+
+		if err != nil {
+			return fmt.Errorf("Recieved an error when attempting to load %s:  %s", asg, err)
+		}
+
+		if targetGroupCount != len(actual.AutoScalingGroups[0].TargetGroupARNs) {
+			return fmt.Errorf("Error: ASG has the wrong number of Target Groups associated.  Expected [%d] but got [%d]", targetGroupCount, len(actual.AutoScalingGroups[0].TargetGroupARNs))
+		}
+
+		return nil
+	}
+}
+
+func testAccAWSAutoscalingAttachment_alb(rInt int) string {
+	return fmt.Sprintf(`
+resource "aws_alb_target_group" "test" {
+  name = "test-alb-%d"
+  port = 443
+  protocol = "HTTPS"
+  vpc_id = "${aws_vpc.test.id}"
+
+  deregistration_delay = 200
+
+  stickiness {
+    type = "lb_cookie"
+    cookie_duration = 10000
+  }
+
+  health_check {
+    path = "/health"
+    interval = 60
+    port = 8081
+    protocol = "HTTP"
+    timeout = 3
+    healthy_threshold = 3
+    unhealthy_threshold = 3
+    matcher = "200-299"
+  }
+
+  tags {
+    TestName = "TestAccAWSALBTargetGroup_basic"
+  }
+}
+
+resource "aws_alb_target_group" "another_test" {
+  name = "atest-alb-%d"
+  port = 443
+  protocol = "HTTPS"
+  vpc_id = "${aws_vpc.test.id}"
+
+  deregistration_delay = 200
+
+  stickiness {
+    type = "lb_cookie"
+    cookie_duration = 10000
+  }
+
+  health_check {
+    path = "/health"
+    interval = 60
+    port = 8081
+    protocol = "HTTP"
+    timeout = 3
+    healthy_threshold = 3
+    unhealthy_threshold = 3
+    matcher = "200-299"
+  }
+
+  tags {
+    TestName = "TestAccAWSALBTargetGroup_basic"
+  }
+}
+
+resource "aws_autoscaling_group" "asg" {
+  availability_zones = ["us-west-2a", "us-west-2b", "us-west-2c"]
+  name = "asg-lb-assoc-terraform-test_%d"
+  max_size = 1
+  min_size = 0
+  desired_capacity = 0
+  health_check_grace_period = 300
+  force_delete = true
+  launch_configuration = "${aws_launch_configuration.as_conf.name}"
+
+  tag {
+    key = "Name"
+    value = "terraform-asg-lg-assoc-test"
+    propagate_at_launch = true
+  }
+}
+
+resource "aws_launch_configuration" "as_conf" {
+    name = "test_config_%d"
+    image_id = "ami-f34032c3"
+    instance_type = "t1.micro"
+}
+
+resource "aws_vpc" "test" {
+  cidr_block = "10.0.0.0/16"
+
+  tags {
+    TestName = "TestAccAWSALBTargetGroup_basic"
+  }
+}
+`, rInt, rInt, rInt, rInt)
+}
+
+func testAccAWSAutoscalingAttachment_elb(rInt int) string {
 	return fmt.Sprintf(`
 resource "aws_elb" "foo" {
   availability_zones = ["us-west-2a", "us-west-2b", "us-west-2c"]
@@ -131,18 +288,34 @@ resource "aws_autoscaling_group" "asg" {
 }`, rInt, rInt)
 }
 
-func testAccAWSAutoscalingAttachment_associated(rInt int) string {
+func testAccAWSAutoscalingAttachment_elb_associated(rInt int) string {
-	return testAccAWSAutoscalingAttachment_basic(rInt) + `
+	return testAccAWSAutoscalingAttachment_elb(rInt) + `
 resource "aws_autoscaling_attachment" "asg_attachment_foo" {
   autoscaling_group_name = "${aws_autoscaling_group.asg.id}"
   elb                    = "${aws_elb.foo.id}"
 }`
 }
 
-func testAccAWSAutoscalingAttachment_double_associated(rInt int) string {
+func testAccAWSAutoscalingAttachment_alb_associated(rInt int) string {
-	return testAccAWSAutoscalingAttachment_associated(rInt) + `
+	return testAccAWSAutoscalingAttachment_alb(rInt) + `
+resource "aws_autoscaling_attachment" "asg_attachment_foo" {
+  autoscaling_group_name = "${aws_autoscaling_group.asg.id}"
+  alb_target_group_arn   = "${aws_alb_target_group.test.arn}"
+}`
+}
+
+func testAccAWSAutoscalingAttachment_elb_double_associated(rInt int) string {
+	return testAccAWSAutoscalingAttachment_elb_associated(rInt) + `
 resource "aws_autoscaling_attachment" "asg_attachment_bar" {
   autoscaling_group_name = "${aws_autoscaling_group.asg.id}"
   elb                    = "${aws_elb.bar.id}"
 }`
 }
+
+func testAccAWSAutoscalingAttachment_alb_double_associated(rInt int) string {
+	return testAccAWSAutoscalingAttachment_alb_associated(rInt) + `
+resource "aws_autoscaling_attachment" "asg_attachment_bar" {
+  autoscaling_group_name = "${aws_autoscaling_group.asg.id}"
+  alb_target_group_arn   = "${aws_alb_target_group.another_test.arn}"
+}`
+}

builtin/providers/aws/resource_aws_autoscaling_group.go

@@ -58,57 +58,57 @@ func resourceAwsAutoscalingGroup() *schema.Resource {
 				},
 			},
 
-			"launch_configuration": &schema.Schema{
+			"launch_configuration": {
 				Type:     schema.TypeString,
 				Required: true,
 			},
 
-			"desired_capacity": &schema.Schema{
+			"desired_capacity": {
 				Type:     schema.TypeInt,
 				Optional: true,
 				Computed: true,
 			},
 
-			"min_elb_capacity": &schema.Schema{
+			"min_elb_capacity": {
 				Type:     schema.TypeInt,
 				Optional: true,
 			},
 
-			"min_size": &schema.Schema{
+			"min_size": {
 				Type:     schema.TypeInt,
 				Required: true,
 			},
 
-			"max_size": &schema.Schema{
+			"max_size": {
 				Type:     schema.TypeInt,
 				Required: true,
 			},
 
-			"default_cooldown": &schema.Schema{
+			"default_cooldown": {
 				Type:     schema.TypeInt,
 				Optional: true,
 				Computed: true,
 			},
 
-			"force_delete": &schema.Schema{
+			"force_delete": {
 				Type:     schema.TypeBool,
 				Optional: true,
 				Default:  false,
 			},
 
-			"health_check_grace_period": &schema.Schema{
+			"health_check_grace_period": {
 				Type:     schema.TypeInt,
 				Optional: true,
 				Default:  300,
 			},
 
-			"health_check_type": &schema.Schema{
+			"health_check_type": {
 				Type:     schema.TypeString,
 				Optional: true,
 				Computed: true,
 			},
 
-			"availability_zones": &schema.Schema{
+			"availability_zones": {
 				Type:     schema.TypeSet,
 				Optional: true,
 				Computed: true,
@@ -116,12 +116,12 @@ func resourceAwsAutoscalingGroup() *schema.Resource {
 				Set:      schema.HashString,
 			},
 
-			"placement_group": &schema.Schema{
+			"placement_group": {
 				Type:     schema.TypeString,
 				Optional: true,
 			},
 
-			"load_balancers": &schema.Schema{
+			"load_balancers": {
 				Type:     schema.TypeSet,
 				Optional: true,
 				Computed: true,
@@ -129,7 +129,7 @@ func resourceAwsAutoscalingGroup() *schema.Resource {
 				Set:      schema.HashString,
 			},
 
-			"vpc_zone_identifier": &schema.Schema{
+			"vpc_zone_identifier": {
 				Type:     schema.TypeSet,
 				Optional: true,
 				Computed: true,
@@ -137,13 +137,13 @@ func resourceAwsAutoscalingGroup() *schema.Resource {
 				Set:      schema.HashString,
 			},
 
-			"termination_policies": &schema.Schema{
+			"termination_policies": {
 				Type:     schema.TypeList,
 				Optional: true,
 				Elem:     &schema.Schema{Type: schema.TypeString},
 			},
 
-			"wait_for_capacity_timeout": &schema.Schema{
+			"wait_for_capacity_timeout": {
 				Type:     schema.TypeString,
 				Optional: true,
 				Default:  "10m",
@@ -162,12 +162,12 @@ func resourceAwsAutoscalingGroup() *schema.Resource {
 				},
 			},
 
-			"wait_for_elb_capacity": &schema.Schema{
+			"wait_for_elb_capacity": {
 				Type:     schema.TypeInt,
 				Optional: true,
 			},
 
-			"enabled_metrics": &schema.Schema{
+			"enabled_metrics": {
 				Type:     schema.TypeSet,
 				Optional: true,
 				Elem:     &schema.Schema{Type: schema.TypeString},
@@ -181,31 +181,32 @@ func resourceAwsAutoscalingGroup() *schema.Resource {
 				Set:      schema.HashString,
 			},
 
-			"metrics_granularity": &schema.Schema{
+			"metrics_granularity": {
 				Type:     schema.TypeString,
 				Optional: true,
 				Default:  "1Minute",
 			},
 
-			"protect_from_scale_in": &schema.Schema{
+			"protect_from_scale_in": {
 				Type:     schema.TypeBool,
 				Optional: true,
 				Default:  false,
 			},
 
-			"target_group_arns": &schema.Schema{
+			"target_group_arns": {
 				Type:     schema.TypeSet,
 				Optional: true,
+				Computed: true,
 				Elem:     &schema.Schema{Type: schema.TypeString},
 				Set:      schema.HashString,
 			},
 
-			"arn": &schema.Schema{
+			"arn": {
 				Type:     schema.TypeString,
 				Computed: true,
 			},
 
-			"initial_lifecycle_hook": &schema.Schema{
+			"initial_lifecycle_hook": {
 				Type:     schema.TypeSet,
 				Optional: true,
 				Elem: &schema.Resource{
@@ -445,6 +446,8 @@ func resourceAwsAutoscalingGroupRead(d *schema.ResourceData, meta interface{}) e
 	d.Set("health_check_type", g.HealthCheckType)
 	d.Set("launch_configuration", g.LaunchConfigurationName)
 	d.Set("load_balancers", flattenStringList(g.LoadBalancerNames))
+	d.Set("target_group_arns", flattenStringList(g.TargetGroupARNs))
+
 	if err := d.Set("suspended_processes", flattenAsgSuspendedProcesses(g.SuspendedProcesses)); err != nil {
 		log.Printf("[WARN] Error setting suspended_processes for %q: %s", d.Id(), err)
 	}

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

@@ -16,6 +16,7 @@ an ELB), and an [AutoScaling Group resource](autoscaling_group.html) with
 `load_balancers` defined in-line. At this time you cannot use an ASG with in-line
 load balancers in conjunction with an ASG Attachment resource. Doing so will cause a
 conflict and will overwrite attachments.
+
 ## Example Usage
 
 ```
@@ -26,10 +27,19 @@ resource "aws_autoscaling_attachment" "asg_attachment_bar" {
 }
 ```
 
+```
+# Create a new ALB Target Group attachment
+resource "aws_autoscaling_attachment" "asg_attachment_bar" {
+  autoscaling_group_name = "${aws_autoscaling_group.asg.id}"
+  alb_target_group_arn   = "${aws_alb_target_group.test.arn}"
+}
+```
+
 ## Argument Reference
 
 The following arguments are supported:
 
 * `autoscaling_group_name` - (Required) Name of ASG to associate with the ELB.
-* `elb` - (Required) The name of the ELB.
+* `elb` - (Optional) The name of the ELB.
+* `alb_target_group_arn` - (Optional) The ARN of an ALB Target Group.