AWS Auto Scaling Group (ASG) Terraform module

Terraform module which creates Auto Scaling resources on AWS.

These types of resources are supported:

• Launch Configuration
• Auto Scaling Group

Usage

module "asg" {
  source = "life360/autoscaling/aws"

  name = "service"

  # Launch configuration
  lc_name = "example-lc"

  image_id        = "ami-ebd02392"
  instance_type   = "t2.micro"
  security_groups = ["sg-12345678"]

  ebs_block_device = [
    {
      device_name           = "/dev/xvdz"
      volume_type           = "gp2"
      volume_size           = "50"
      delete_on_termination = true
    },
  ]

  root_block_device = [
    {
      volume_size = "50"
      volume_type = "gp2"
    },
  ]

  # Auto scaling group
  asg_name                  = "example-asg"
  vpc_zone_identifier       = ["subnet-1235678", "subnet-87654321"]
  health_check_type         = "EC2"
  min_size                  = 0
  max_size                  = 1
  desired_capacity          = 1
  wait_for_capacity_timeout = 0

  tags = [
    {
      key                 = "Environment"
      value               = "dev"
      propagate_at_launch = true
    },
    {
      key                 = "Project"
      value               = "megasecret"
      propagate_at_launch = true
    },
  ]

  tags_as_map = {
    extra_tag1 = "extra_value1"
    extra_tag2 = "extra_value2"
  }
}

Conditional creation

Normally this module creates both Auto Scaling Group (ASG) and Launch Configuration (LC), and connect them together. It is possible to customize this behaviour passing different parameters to this module:

1. To create ASG, but not LC. Associate ASG with an existing LC:

create_lc = false
launch_configuration = "existing-launch-configuration"

1. To create LC, but not ASG. Outputs may produce errors.

create_asg = false

1. To create ASG with initial lifecycle hook

create_asg_with_initial_lifecycle_hook = true

initial_lifecycle_hook_name                  = "NameOfLifeCycleHook"
initial_lifecycle_hook_lifecycle_transition  = "autoscaling:EC2_INSTANCE_TERMINATING"
initial_lifecycle_hook_notification_metadata =<<EOF
{
  "foo": "bar"
}
EOF

1. To disable creation of both resources (LC and ASG) you can specify both arguments create_lc = false and create_asg = false. Sometimes you need to use this way to create resources in modules conditionally but Terraform does not allow to use count inside module block.

Tags

There are two ways to specify tags for auto-scaling group in this module - tags and tags_as_map. See examples/asg_ec2/main.tf for example.

Examples

• Auto Scaling Group without ELB
• Auto Scaling Group with ELB
• Auto Scaling Group with external Launch Configuration

Inputs

Name	Description	Type	Default	Required
asg_name	Creates a unique name for autoscaling group beginning with the specified prefix	string	``	no
associate_public_ip_address	Associate a public ip address with an instance in a VPC	string	false	no
create_asg	Whether to create autoscaling group	string	true	no
create_asg_with_initial_lifecycle_hook	Create an ASG with initial lifecycle hook	string	false	no
create_lc	Whether to create launch configuration	string	true	no
default_cooldown	The amount of time, in seconds, after a scaling activity completes before another scaling activity can start	string	300	no
desired_capacity	The number of Amazon EC2 instances that should be running in the group	string	-	yes
ebs_block_device	Additional EBS block devices to attach to the instance	list	<list>	no
ebs_optimized	If true, the launched EC2 instance will be EBS-optimized	string	false	no
enable_monitoring	Enables/disables detailed monitoring. This is enabled by default.	string	true	no
enabled_metrics	A list of metrics to collect. The allowed values are GroupMinSize, GroupMaxSize, GroupDesiredCapacity, GroupInServiceInstances, GroupPendingInstances, GroupStandbyInstances, GroupTerminatingInstances, GroupTotalInstances	list	<list>	no
ephemeral_block_device	Customize Ephemeral (also known as 'Instance Store') volumes on the instance	list	<list>	no
force_delete	Allows deleting the autoscaling group without waiting for all instances in the pool to terminate. You can force an autoscaling group to delete even if it's in the process of scaling a resource. Normally, Terraform drains all the instances before deleting the group. This bypasses that behavior and potentially leaves resources dangling	string	false	no
health_check_grace_period	Time (in seconds) after instance comes into service before checking health	string	300	no
health_check_type	Controls how health checking is done. Values are - EC2 and ELB	string	-	yes
iam_instance_profile	The IAM instance profile to associate with launched instances	string	``	no
image_id	The EC2 image ID to launch	string	``	no
initial_lifecycle_hook_default_result	Defines the action the Auto Scaling group should take when the lifecycle hook timeout elapses or if an unexpected failure occurs. The value for this parameter can be either CONTINUE or ABANDON	string	ABANDON	no
initial_lifecycle_hook_heartbeat_timeout	Defines the amount of time, in seconds, that can elapse before the lifecycle hook times out. When the lifecycle hook times out, Auto Scaling performs the action defined in the DefaultResult parameter	string	60	no
initial_lifecycle_hook_lifecycle_transition	The instance state to which you want to attach the initial lifecycle hook	string	``	no
initial_lifecycle_hook_name	The name of initial lifecycle hook	string	``	no
initial_lifecycle_hook_notification_metadata	Contains additional information that you want to include any time Auto Scaling sends a message to the notification target	string	``	no
initial_lifecycle_hook_notification_target_arn	The ARN of the notification target that Auto Scaling will use to notify you when an instance is in the transition state for the lifecycle hook. This ARN target can be either an SQS queue or an SNS topic	string	``	no
initial_lifecycle_hook_role_arn	The ARN of the IAM role that allows the Auto Scaling group to publish to the specified notification target	string	``	no
instance_type	The size of instance to launch	string	``	no
key_name	The key name that should be used for the instance	string	``	no
launch_configuration	The name of the launch configuration to use (if it is created outside of this module)	string	``	no
lc_name	Creates a unique name for launch configuration beginning with the specified prefix	string	``	no
load_balancers	A list of elastic load balancer names to add to the autoscaling group names	list	<list>	no
max_size	The maximum size of the auto scale group	string	-	yes
metrics_granularity	The granularity to associate with the metrics to collect. The only valid value is 1Minute	string	1Minute	no
min_elb_capacity	Setting this causes Terraform to wait for this number of instances to show up healthy in the ELB only on creation. Updates will not wait on ELB instance number changes	string	0	no
min_size	The minimum size of the auto scale group	string	-	yes
name	Creates a unique name beginning with the specified prefix	string	-	yes
placement_group	The name of the placement group into which you'll launch your instances, if any	string	``	no
placement_tenancy	The tenancy of the instance. Valid values are 'default' or 'dedicated'	string	default	no
protect_from_scale_in	Allows setting instance protection. The autoscaling group will not select instances with this setting for termination during scale in events.	string	false	no
recreate_asg_when_lc_changes	Whether to recreate an autoscaling group when launch configuration changes	string	false	no
root_block_device	Customize details about the root block device of the instance	list	<list>	no
security_groups	A list of security group IDs to assign to the launch configuration	list	<list>	no
spot_price	The price to use for reserving spot instances	string	``	no
suspended_processes	A list of processes to suspend for the AutoScaling Group. The allowed values are Launch, Terminate, HealthCheck, ReplaceUnhealthy, AZRebalance, AlarmNotification, ScheduledActions, AddToLoadBalancer. Note that if you suspend either the Launch or Terminate process types, it can prevent your autoscaling group from functioning properly.	list	<list>	no
tags	A list of tag blocks. Each element should have keys named key, value, and propagate_at_launch.	list	<list>	no
tags_as_map	A map of tags and values in the same format as other resources accept. This will be converted into the non-standard format that the aws_autoscaling_group requires.	map	<map>	no
target_group_arns	A list of aws_alb_target_group ARNs, for use with Application Load Balancing	list	<list>	no
termination_policies	A list of policies to decide how the instances in the auto scale group should be terminated. The allowed values are OldestInstance, NewestInstance, OldestLaunchConfiguration, ClosestToNextInstanceHour, Default	list	<list>	no
user_data	The user data to provide when launching the instance	string		no
vpc_zone_identifier	A list of subnet IDs to launch resources in	list	-	yes
wait_for_capacity_timeout	A maximum duration that Terraform should wait for ASG instances to be healthy before timing out. (See also Waiting for Capacity below.) Setting this to '0' causes Terraform to skip all Capacity Waiting behavior.	string	10m	no
wait_for_elb_capacity	Setting this will cause Terraform to wait for exactly this number of healthy instances in all attached load balancers on both create and update operations. Takes precedence over min_elb_capacity behavior.	string	false	no

Outputs

Name	Description
this_autoscaling_group_arn	The ARN for this AutoScaling Group
this_autoscaling_group_default_cooldown	Time between a scaling activity and the succeeding scaling activity
this_autoscaling_group_desired_capacity	The number of Amazon EC2 instances that should be running in the group
this_autoscaling_group_health_check_grace_period	Time after instance comes into service before checking health
this_autoscaling_group_health_check_type	EC2 or ELB. Controls how health checking is done
this_autoscaling_group_id	The autoscaling group id
this_autoscaling_group_max_size	The maximum size of the autoscale group
this_autoscaling_group_min_size	The minimum size of the autoscale group
this_autoscaling_group_name	The autoscaling group name
this_launch_configuration_id	The ID of the launch configuration
this_launch_configuration_name	The name of the launch configuration

Authors

Module managed by Anton Babenko.

Thanks to Jamie-BitFlight who added possibility to specify unlimited numbers of tags.

License

Apache 2 Licensed. See LICENSE for full details.