https://github.com/hashicorp/terraform/issues/13517

main.tf

resource "aws_cloudformation_stack" "autoscaling_group" {
  name = "${var.name}"
  on_failure = "${var.asg_on_failure}"

  # CloudFormation templates are more verbose and harder to read than Terraform templates, especially when crammed into
  # a Terraform template. Since they are JSON, comments are not supported either. The CloudFormation template below
  # creates just a single resource: an Auto Scaling Group. It configures a CreationPolicy and UpdatePolicy for it and
  # spits out its computed name as an output.
  template_body = <<EOF
{
  "Resources": {
    "${var.name}": {
      "Type": "AWS::AutoScaling::AutoScalingGroup",
      "Properties": {
        "LaunchConfigurationName": "${var.launch_configuration_name}",
        "MinSize": "${var.min_size}",
        "MaxSize": "${var.max_size}",
        "VPCZoneIdentifier": [${join(",", formatlist("\"%s\"", compact(var.vpc_subnet_ids)))}],
        "HealthCheckGracePeriod": ${var.health_check_grace_period},
        "TerminationPolicies": ["OldestLaunchConfiguration", "OldestInstance"],
        "Tags": [{
          "Key": "Name",
          "Value": "${var.name}",
          "PropagateAtLaunch": true
        }]
      },
      "CreationPolicy": {
        "ResourceSignal": {
          "Timeout": "${var.rolling_deploy_pause_time}",
          "Count": ${var.creation_signal_count}
        }
      },
      "UpdatePolicy": {
        "AutoScalingRollingUpdate": {
          "MinInstancesInService": ${var.rolling_deploy_min_instances_in_service},
          "MaxBatchSize": ${var.rolling_deploy_max_batch_size},
          "PauseTime": "${var.rolling_deploy_pause_time}",
          ${module.if_wait_on_resource_signals.result}
        }
      }
    }
  },
  "Outputs": {
    "AsgName": {
      "Description": "The name of the auto scaling group",
       "Value": {"Ref": "${var.name}"}
    }
  }
}
EOF
}


resource "aws_launch_configuration" "launch_configuration" {
  name_prefix = "${var.name}-"
  image_id = "${var.ami}"
  instance_type = "${var.instance_type}"
  iam_instance_profile = "${aws_iam_instance_profile.instance_profile.name}"
  key_name = "${var.keypair_name}"
  security_groups = ["${aws_security_group.lc_security_group.id}"]
  user_data = "${data.template_file.user_data.rendered}"

  lifecycle {
    create_before_destroy = true
  }
}