Module: ec2-autoscale-group

Terraform module to provision Auto Scaling Group and Launch Template on AWS.

The module also creates AutoScaling Policies and CloudWatch Metric Alarms to monitor CPU utilization on the EC2 instances and scale the number of instance in the AutoScaling Group up or down. If you don't want to use the provided functionality, or want to provide your own policies, disable it by setting the variable autoscaling_policies_enabled to false.

At present, although you can set the created AutoScaling Policy type to any legal value, in practice only SimpleScaling is supported. To use a StepScaling or TargetTrackingScaling policy, create it yourself and then pass it in the alarm_actions field of custom_alarms.

Usage

locals {
  userdata = <<-USERDATA
    #!/bin/bash
    cat <<"__EOF__" > /home/ec2-user/.ssh/config
    Host *
      StrictHostKeyChecking no
    __EOF__
    chmod 600 /home/ec2-user/.ssh/config
    chown ec2-user:ec2-user /home/ec2-user/.ssh/config
  USERDATA
}

module "autoscale_group" {
  source = "cloudposse/ec2-autoscale-group/aws"
  # Cloud Posse recommends pinning every module to a specific version
  # version = "x.x.x"

  namespace   = var.namespace
  stage       = var.stage
  environment = var.environment
  name        = var.name

  image_id                    = "ami-08cab282f9979fc7a"
  instance_type               = "t2.small"
  security_group_ids          = ["sg-xxxxxxxx"]
  subnet_ids                  = ["subnet-xxxxxxxx", "subnet-yyyyyyyy", "subnet-zzzzzzzz"]
  health_check_type           = "EC2"
  min_size                    = 2
  max_size                    = 3
  wait_for_capacity_timeout   = "5m"
  associate_public_ip_address = true
  user_data_base64            = base64encode(local.userdata)

  # All inputs to `block_device_mappings` have to be defined
  block_device_mappings = [
    {
      device_name  = "/dev/sda1"
      no_device    = "false"
      virtual_name = "root"
      ebs = {
        encrypted             = true
        volume_size           = 200
        delete_on_termination = true
        iops                  = null
        kms_key_id            = null
        snapshot_id           = null
        volume_type           = "standard"
      }
    }
  ]

  tags = {
    Tier              = "1"
    KubernetesCluster = "us-west-2.testing.cloudposse.co"
  }

  # Auto-scaling policies and CloudWatch metric alarms
  autoscaling_policies_enabled           = true
  cpu_utilization_high_threshold_percent = "70"
  cpu_utilization_low_threshold_percent  = "20"
}

To enable custom_alerts the map needs to be defined like so :

alarms = {
    alb_scale_up = {
      alarm_name                = "${module.default_label.id}-alb-target-response-time-for-scale-up"
      comparison_operator       = "GreaterThanThreshold"
      evaluation_periods        = var.alb_target_group_alarms_evaluation_periods
      metric_name               = "TargetResponseTime"
      namespace                 = "AWS/ApplicationELB"
      period                    = var.alb_target_group_alarms_period
      statistic                 = "Average"
      threshold                 = var.alb_target_group_alarms_response_time_max_threshold
      dimensions_name           = "LoadBalancer"
      dimensions_target         = data.alb.arn_suffix
      treat_missing_data        = "missing"
      ok_actions                = var.alb_target_group_alarms_ok_actions
      insufficient_data_actions = var.alb_target_group_alarms_insufficient_data_actions
      alarm_description         = "ALB Target response time is over ${var.alb_target_group_alarms_response_time_max_threshold} for more than ${var.alb_target_group_alarms_period}"
      alarm_actions             = [module.autoscaling.scale_up_policy_arn]
    }
}

All those keys are required to be there so if the alarm you are setting does not requiere one or more keys you can just set to empty but do not remove the keys otherwise you could get a weird merge error due to the maps being of different sizes.

Requirements

Name	Version
terraform	>= 1.3
aws	>= 5.16

Providers

Name	Version
aws	>= 5.16

Modules

Name	Source	Version
this	cloudposse/label/null	0.25.0

Resources

Name	Type
aws_autoscaling_group.default	resource
aws_autoscaling_policy.scale_down	resource
aws_autoscaling_policy.scale_up	resource
aws_cloudwatch_metric_alarm.all_alarms	resource
aws_launch_template.default	resource
aws_subnet.this	data source

Inputs

Name	Description	Type	Default	Required
additional_tag_map	Additional key-value pairs to add to each map in tags_as_list_of_maps. Not added to tags or id. This is for some rare cases where resources want additional configuration of tags and therefore take a list of maps with tag key, value, and additional configuration.	map(string)	{}	no
associate_public_ip_address	Associate a public IP address with an instance in a VPC. If network_interface_id is specified, this can only be false (see here for more info: https://stackoverflow.com/a/76808361).	bool	false	no
attributes	ID element. Additional attributes (e.g. workers or cluster) to add to id, in the order they appear in the list. New attributes are appended to the end of the list. The elements of the list are joined by the delimiter and treated as a single ID element.	list(string)	[]	no
autoscaling_policies_enabled	Whether to create aws_autoscaling_policy and aws_cloudwatch_metric_alarm resources to control Auto Scaling	bool	true	no
block_device_mappings	Specify volumes to attach to the instance besides the volumes specified by the AMI	list(object({ device_name = optional(string) no_device = optional(bool) virtual_name = optional(string) ebs = object({ delete_on_termination = optional(bool) encrypted = optional(bool) iops = optional(number) throughput = optional(number) kms_key_id = optional(string) snapshot_id = optional(string) volume_size = optional(number) volume_type = optional(string) }) }))	[]	no
capacity_rebalance	Indicates whether capacity rebalance is enabled. Otherwise, capacity rebalance is disabled.	bool	false	no
context	Single object for setting entire context at once. See description of individual variables for details. Leave string and numeric variables as null to use default value. Individual variable settings (non-null) override settings in context object, except for attributes, tags, and additional_tag_map, which are merged.	any	{ "additional_tag_map": {}, "attributes": [], "delimiter": null, "descriptor_formats": {}, "enabled": true, "environment": null, "id_length_limit": null, "label_key_case": null, "label_order": [], "label_value_case": null, "labels_as_tags": [ "unset" ], "name": null, "namespace": null, "regex_replace_chars": null, "stage": null, "tags": {}, "tenant": null }	no
cpu_utilization_high_evaluation_periods	The number of periods over which data is compared to the specified threshold	number	2	no
cpu_utilization_high_period_seconds	The period in seconds over which the specified statistic is applied	number	300	no
cpu_utilization_high_statistic	The statistic to apply to the alarm's associated metric. Either of the following is supported: SampleCount, Average, Sum, Minimum, Maximum	string	"Average"	no
cpu_utilization_high_threshold_percent	The value against which the specified statistic is compared	number	90	no
cpu_utilization_low_evaluation_periods	The number of periods over which data is compared to the specified threshold	number	2	no
cpu_utilization_low_period_seconds	The period in seconds over which the specified statistic is applied	number	300	no
cpu_utilization_low_statistic	The statistic to apply to the alarm's associated metric. Either of the following is supported: SampleCount, Average, Sum, Minimum, Maximum	string	"Average"	no
cpu_utilization_low_threshold_percent	The value against which the specified statistic is compared	number	10	no
credit_specification	Customize the credit specification of the instances	object({ cpu_credits = string })	null	no
custom_alarms	Map of custom CloudWatch alarms configurations	map(object({ alarm_name = string comparison_operator = string evaluation_periods = string metric_name = string namespace = string period = string statistic = string extended_statistic = string threshold = string treat_missing_data = string ok_actions = list(string) insufficient_data_actions = list(string) dimensions_name = string dimensions_target = string alarm_description = string alarm_actions = list(string) }))	{}	no
default_alarms_enabled	Enable or disable cpu and memory Cloudwatch alarms	bool	true	no
default_cooldown	The amount of time, in seconds, after a scaling activity completes before another scaling activity can start	number	300	no
delimiter	Delimiter to be used between ID elements. Defaults to - (hyphen). Set to "" to use no delimiter at all.	string	null	no
descriptor_formats	Describe additional descriptors to be output in the descriptors output map. Map of maps. Keys are names of descriptors. Values are maps of the form {<br/> format = string<br/> labels = list(string)<br/>} (Type is any so the map values can later be enhanced to provide additional options.) format is a Terraform format string to be passed to the format() function. labels is a list of labels, in order, to pass to format() function. Label values will be normalized before being passed to format() so they will be identical to how they appear in id. Default is {} (descriptors output will be empty).	any	{}	no
desired_capacity	The number of Amazon EC2 instances that should be running in the group, if not set will use min_size as value	number	null	no
disable_api_termination	If true, enables EC2 Instance Termination Protection	bool	false	no
ebs_optimized	If true, the launched EC2 instance will be EBS-optimized	bool	false	no
elastic_gpu_specifications	Specifications of Elastic GPU to attach to the instances	object({ type = string })	null	no
enable_monitoring	Enable/disable detailed monitoring	bool	true	no
enabled	Set to false to prevent the module from creating any resources	bool	null	no
enabled_metrics	A list of metrics to collect. The allowed values are GroupMinSize, GroupMaxSize, GroupDesiredCapacity, GroupInServiceInstances, GroupPendingInstances, GroupStandbyInstances, GroupTerminatingInstances, GroupTotalInstances	list(string)	[ "GroupMinSize", "GroupMaxSize", "GroupDesiredCapacity", "GroupInServiceInstances", "GroupPendingInstances", "GroupStandbyInstances", "GroupTerminatingInstances", "GroupTotalInstances" ]	no
environment	ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'	string	null	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	bool	false	no
health_check_grace_period	Time (in seconds) after instance comes into service before checking health	number	300	no
health_check_type	Controls how health checking is done. Valid values are EC2 or ELB	string	"EC2"	no
iam_instance_profile_name	The IAM instance profile name to associate with launched instances	string	""	no
id_length_limit	Limit id to this many characters (minimum 6). Set to 0 for unlimited length. Set to null for keep the existing setting, which defaults to 0. Does not affect id_full.	number	null	no
image_id	The EC2 image ID to launch	string	""	no
instance_initiated_shutdown_behavior	Shutdown behavior for the instances. Can be stop or terminate	string	"terminate"	no
instance_market_options	The market (purchasing) option for the instances	object({ market_type = string spot_options = optional(object({ block_duration_minutes = optional(number) instance_interruption_behavior = optional(string) max_price = optional(number) spot_instance_type = optional(string) valid_until = optional(string) })) })	null	no
instance_refresh	The instance refresh definition	object({ strategy = string preferences = optional(object({ instance_warmup = optional(number, null) min_healthy_percentage = optional(number, null) skip_matching = optional(bool, null) auto_rollback = optional(bool, null) scale_in_protected_instances = optional(string, null) standby_instances = optional(string, null) }), null) triggers = optional(list(string), []) })	null	no
instance_reuse_policy	If warm pool and this block are configured, instances in the Auto Scaling group can be returned to the warm pool on scale in. The default is to terminate instances in the Auto Scaling group when the group scales in.	object({ reuse_on_scale_in = bool })	null	no
instance_type	Instance type to launch	string	n/a	yes
key_name	The SSH key name that should be used for the instance	string	""	no
label_key_case	Controls the letter case of the tags keys (label names) for tags generated by this module. Does not affect keys of tags passed in via the tags input. Possible values: lower, title, upper. Default value: title.	string	null	no
label_order	The order in which the labels (ID elements) appear in the id. Defaults to ["namespace", "environment", "stage", "name", "attributes"]. You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present.	list(string)	null	no
label_value_case	Controls the letter case of ID elements (labels) as included in id, set as tag values, and output by this module individually. Does not affect values of tags passed in via the tags input. Possible values: lower, title, upper and none (no transformation). Set this to title and set delimiter to "" to yield Pascal Case IDs. Default value: lower.	string	null	no
labels_as_tags	Set of labels (ID elements) to include as tags in the tags output. Default is to include all labels. Tags with empty values will not be included in the tags output. Set to [] to suppress all generated tags. Notes: The value of the name tag, if included, will be the id, not the name. Unlike other null-label inputs, the initial setting of labels_as_tags cannot be changed in later chained modules. Attempts to change it will be silently ignored.	set(string)	[ "default" ]	no
launch_template_version	Launch template version. Can be version number, $Latest or $Default	string	"$Latest"	no
load_balancers	A list of elastic load balancer names to add to the autoscaling group names. Only valid for classic load balancers. For ALBs, use target_group_arns instead	list(string)	[]	no
max_instance_lifetime	The maximum amount of time, in seconds, that an instance can be in service, values must be either equal to 0 or between 604800 and 31536000 seconds	number	null	no
max_size	The maximum size of the autoscale group	number	n/a	yes
metadata_http_endpoint_enabled	Set false to disable the Instance Metadata Service.	bool	true	no
metadata_http_protocol_ipv6_enabled	Set true to enable IPv6 in the launch template.	bool	false	no
metadata_http_put_response_hop_limit	The desired HTTP PUT response hop limit (between 1 and 64) for Instance Metadata Service requests. The default is 2 to support containerized workloads.	number	2	no
metadata_http_tokens_required	Set true to require IMDS session tokens, disabling Instance Metadata Service Version 1.	bool	true	no
metadata_instance_metadata_tags_enabled	Set true to enable metadata tags in the launch template.	bool	false	no
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	number	0	no
min_size	The minimum size of the autoscale group	number	n/a	yes
mixed_instances_policy	policy to used mixed group of on demand/spot of differing types. Launch template is automatically generated. https://www.terraform.io/docs/providers/aws/r/autoscaling_group.html#mixed_instances_policy-1	object({ instances_distribution = optional(object({ on_demand_allocation_strategy = string on_demand_base_capacity = number on_demand_percentage_above_base_capacity = number spot_allocation_strategy = string spot_instance_pools = number spot_max_price = string })) override = optional(list(object({ instance_type = string weighted_capacity = number }))) })	null	no
name	ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'. This is the only ID element not also included as a tag. The "name" tag is set to the full id string. There is no tag with the value of the name input.	string	null	no
namespace	ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique	string	null	no
network_interface_id	The ID of the network interface to attach. If specified, all the other network_interface block arguments are ignored.	string	null	no
placement	The placement specifications of the instances	object({ affinity = string availability_zone = string group_name = string host_id = string tenancy = string })	null	no
placement_group	The name of the placement group into which you'll launch your instances, if any	string	""	no
protect_from_scale_in	Allows setting instance protection. The autoscaling group will not select instances with this setting for terminination during scale in events	bool	false	no
regex_replace_chars	Terraform regular expression (regex) string. Characters matching the regex will be removed from the ID elements. If not set, "/[^a-zA-Z0-9-]/" is used to remove all characters other than hyphens, letters and digits.	string	null	no
scale_down_adjustment_type	Specifies whether the adjustment is an absolute number or a percentage of the current capacity. Valid values are ChangeInCapacity, ExactCapacity and PercentChangeInCapacity	string	"ChangeInCapacity"	no
scale_down_cooldown_seconds	The amount of time, in seconds, after a scaling activity completes and before the next scaling activity can start	number	300	no
scale_down_policy_type	The scaling policy type. Currently only SimpleScaling is supported	string	"SimpleScaling"	no
scale_down_scaling_adjustment	The number of instances by which to scale. scale_down_scaling_adjustment determines the interpretation of this number (e.g. as an absolute number or as a percentage of the existing Auto Scaling group size). A positive increment adds to the current capacity and a negative value removes from the current capacity	number	-1	no
scale_up_adjustment_type	Specifies whether the adjustment is an absolute number or a percentage of the current capacity. Valid values are ChangeInCapacity, ExactCapacity and PercentChangeInCapacity	string	"ChangeInCapacity"	no
scale_up_cooldown_seconds	The amount of time, in seconds, after a scaling activity completes and before the next scaling activity can start	number	300	no
scale_up_policy_type	The scaling policy type. Currently only SimpleScaling is supported	string	"SimpleScaling"	no
scale_up_scaling_adjustment	The number of instances by which to scale. scale_up_adjustment_type determines the interpretation of this number (e.g. as an absolute number or as a percentage of the existing Auto Scaling group size). A positive increment adds to the current capacity and a negative value removes from the current capacity	number	1	no
security_group_ids	A list of associated security group IDs	list(string)	[]	no
service_linked_role_arn	The ARN of the service-linked role that the ASG will use to call other AWS services	string	""	no
stage	ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'	string	null	no
subnet_ids	A list of subnet IDs to launch resources in	list(string)	n/a	yes
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(string)	[]	no
tag_specifications_resource_types	List of tag specification resource types to tag. Valid values are instance, volume, elastic-gpu and spot-instances-request.	set(string)	[ "instance", "volume" ]	no
tags	Additional tags (e.g. {'BusinessUnit': 'XYZ'}). Neither the tag keys nor the tag values will be modified by this module.	map(string)	{}	no
target_group_arns	A list of aws_alb_target_group ARNs, for use with Application Load Balancing	list(string)	[]	no
tenant	ID element _(Rarely used, not included by default)_. A customer identifier, indicating who this instance of a resource is for	string	null	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(string)	[ "Default" ]	no
update_default_version	Whether to update Default version of Launch template each update	bool	false	no
user_data_base64	The Base64-encoded user data to provide when launching the instances	string	""	no
wait_for_capacity_timeout	A maximum duration that Terraform should wait for ASG instances to be healthy before timing out. 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	number	0	no
warm_pool	If this block is configured, add a Warm Pool to the specified Auto Scaling group. See warm_pool.	object({ pool_state = string min_size = number max_group_prepared_capacity = number })	null	no

Outputs

Name	Description
autoscaling_group_arn	ARN of the AutoScaling Group
autoscaling_group_default_cooldown	Time between a scaling activity and the succeeding scaling activity
autoscaling_group_desired_capacity	The number of Amazon EC2 instances that should be running in the group
autoscaling_group_health_check_grace_period	Time after instance comes into service before checking health
autoscaling_group_health_check_type	EC2 or ELB. Controls how health checking is done
autoscaling_group_id	The AutoScaling Group id
autoscaling_group_max_size	The maximum size of the autoscale group
autoscaling_group_min_size	The minimum size of the autoscale group
autoscaling_group_name	The AutoScaling Group name
autoscaling_group_tags	A list of tag settings associated with the AutoScaling Group
autoscaling_policy_scale_down_arn	ARN of the AutoScaling policy scale down
autoscaling_policy_scale_up_arn	ARN of the AutoScaling policy scale up
launch_template_arn	The ARN of the launch template
launch_template_id	The ID of the launch template