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.

Variables

Required Variables

instance_type (string) required: Instance type to launch
max_size (number) required: The maximum size of the autoscale group
min_size (number) required: The minimum size of the autoscale group
subnet_ids (list(string)) required: A list of subnet IDs to launch resources in

Optional Variables

associate_public_ip_address (bool) optional

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).

Default value: false

autoscaling_policies_enabled (bool) optional

Whether to create aws_autoscaling_policy and aws_cloudwatch_metric_alarm resources to control Auto Scaling

Default value: true

block_device_mappings optional

Specify volumes to attach to the instance besides the volumes specified by the AMI

Type:

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)
})
}))

Default value: [ ]

capacity_rebalance (bool) optional

Indicates whether capacity rebalance is enabled. Otherwise, capacity rebalance is disabled.

Default value: false

cpu_utilization_high_evaluation_periods (number) optional

The number of periods over which data is compared to the specified threshold

Default value: 2

cpu_utilization_high_period_seconds (number) optional

The period in seconds over which the specified statistic is applied

Default value: 300

cpu_utilization_high_statistic (string) optional

The statistic to apply to the alarm's associated metric. Either of the following is supported: SampleCount, Average, Sum, Minimum, Maximum

Default value: "Average"

cpu_utilization_high_threshold_percent (number) optional

The value against which the specified statistic is compared

Default value: 90

cpu_utilization_low_evaluation_periods (number) optional

The number of periods over which data is compared to the specified threshold

Default value: 2

cpu_utilization_low_period_seconds (number) optional

The period in seconds over which the specified statistic is applied

Default value: 300

cpu_utilization_low_statistic (string) optional

The statistic to apply to the alarm's associated metric. Either of the following is supported: SampleCount, Average, Sum, Minimum, Maximum

Default value: "Average"

cpu_utilization_low_threshold_percent (number) optional

The value against which the specified statistic is compared

Default value: 10

credit_specification optional

Customize the credit specification of the instances

Type:

object({
cpu_credits = string
})

Default value: null

custom_alarms optional

Map of custom CloudWatch alarms configurations

Type:

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)
}))

Default value: { }

default_alarms_enabled (bool) optional

Enable or disable cpu and memory Cloudwatch alarms

Default value: true

default_cooldown (number) optional

The amount of time, in seconds, after a scaling activity completes before another scaling activity can start

Default value: 300

desired_capacity (number) optional

The number of Amazon EC2 instances that should be running in the group, if not set will use min_size as value

Default value: null

disable_api_termination (bool) optional

If true, enables EC2 Instance Termination Protection

Default value: false

ebs_optimized (bool) optional

If true, the launched EC2 instance will be EBS-optimized

Default value: false

elastic_gpu_specifications optional

Specifications of Elastic GPU to attach to the instances

Type:

object({
type = string
})

Default value: null

enable_monitoring (bool) optional

Enable/disable detailed monitoring

Default value: true

enabled_metrics (list(string)) optional

A list of metrics to collect. The allowed values are GroupMinSize, GroupMaxSize, GroupDesiredCapacity, GroupInServiceInstances, GroupPendingInstances, GroupStandbyInstances, GroupTerminatingInstances, GroupTotalInstances

Default value:

[
  "GroupMinSize",
  "GroupMaxSize",
  "GroupDesiredCapacity",
  "GroupInServiceInstances",
  "GroupPendingInstances",
  "GroupStandbyInstances",
  "GroupTerminatingInstances",
  "GroupTotalInstances"
]

force_delete (bool) optional

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

Default value: false

health_check_grace_period (number) optional

Time (in seconds) after instance comes into service before checking health

Default value: 300

health_check_type (string) optional

Controls how health checking is done. Valid values are EC2 or ELB

Default value: "EC2"

iam_instance_profile_name (string) optional

The IAM instance profile name to associate with launched instances

Default value: ""

image_id (string) optional

The EC2 image ID to launch

Default value: ""

instance_initiated_shutdown_behavior (string) optional

Shutdown behavior for the instances. Can be stop or terminate

Default value: "terminate"

instance_market_options optional

The market (purchasing) option for the instances

Type:

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)
}))
})

Default value: null

instance_refresh optional

The instance refresh definition

Type:

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), [])
})

Default value: null

instance_reuse_policy optional

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.

Type:

object({
reuse_on_scale_in = bool
})

Default value: null

key_name (string) optional

The SSH key name that should be used for the instance

Default value: ""

launch_template_version (string) optional

Launch template version. Can be version number, $Latest or $Default

Default value: "$Latest"

load_balancers (list(string)) optional

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

Default value: [ ]

max_instance_lifetime (number) optional

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

Default value: null

metadata_http_endpoint_enabled (bool) optional

Set false to disable the Instance Metadata Service.

Default value: true

metadata_http_protocol_ipv6_enabled (bool) optional

Set true to enable IPv6 in the launch template.

Default value: false

metadata_http_put_response_hop_limit (number) optional

The desired HTTP PUT response hop limit (between 1 and 64) for Instance Metadata Service requests.
The default is 2 to support containerized workloads.

Default value: 2

metadata_http_tokens_required (bool) optional

Set true to require IMDS session tokens, disabling Instance Metadata Service Version 1.

Default value: true

metadata_instance_metadata_tags_enabled (bool) optional

Set true to enable metadata tags in the launch template.

Default value: false

metrics_granularity (string) optional

The granularity to associate with the metrics to collect. The only valid value is 1Minute

Default value: "1Minute"

min_elb_capacity (number) optional

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

Default value: 0

mixed_instances_policy optional

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

Type:

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
})))
})

Default value: null

network_interface_id (string) optional

The ID of the network interface to attach. If specified, all the other network_interface block arguments are ignored.

Default value: null

placement optional

The placement specifications of the instances

Type:

object({
affinity          = string
availability_zone = string
group_name        = string
host_id           = string
tenancy           = string
})

Default value: null

placement_group (string) optional

The name of the placement group into which you'll launch your instances, if any

Default value: ""

protect_from_scale_in (bool) optional

Allows setting instance protection. The autoscaling group will not select instances with this setting for terminination during scale in events

Default value: false

scale_down_adjustment_type (string) optional

Specifies whether the adjustment is an absolute number or a percentage of the current capacity. Valid values are ChangeInCapacity, ExactCapacity and PercentChangeInCapacity

Default value: "ChangeInCapacity"

scale_down_cooldown_seconds (number) optional

The amount of time, in seconds, after a scaling activity completes and before the next scaling activity can start

Default value: 300

scale_down_policy_type (string) optional

The scaling policy type. Currently only SimpleScaling is supported

Default value: "SimpleScaling"

scale_down_scaling_adjustment (number) optional

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

Default value: -1

scale_up_adjustment_type (string) optional

Specifies whether the adjustment is an absolute number or a percentage of the current capacity. Valid values are ChangeInCapacity, ExactCapacity and PercentChangeInCapacity

Default value: "ChangeInCapacity"

scale_up_cooldown_seconds (number) optional

The amount of time, in seconds, after a scaling activity completes and before the next scaling activity can start

Default value: 300

scale_up_policy_type (string) optional

The scaling policy type. Currently only SimpleScaling is supported

Default value: "SimpleScaling"

scale_up_scaling_adjustment (number) optional

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

Default value: 1

security_group_ids (list(string)) optional

A list of associated security group IDs

Default value: [ ]

service_linked_role_arn (string) optional

The ARN of the service-linked role that the ASG will use to call other AWS services

Default value: ""

suspended_processes (list(string)) optional

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.

Default value: [ ]

tag_specifications_resource_types (set(string)) optional

List of tag specification resource types to tag. Valid values are instance, volume, elastic-gpu and spot-instances-request.

Default value:

[
  "instance",
  "volume"
]

target_group_arns (list(string)) optional

A list of aws_alb_target_group ARNs, for use with Application Load Balancing

Default value: [ ]

termination_policies (list(string)) optional

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

Default value:

[
  "Default"
]

update_default_version (bool) optional

Whether to update Default version of Launch template each update

Default value: false

user_data_base64 (string) optional

The Base64-encoded user data to provide when launching the instances

Default value: ""

wait_for_capacity_timeout (string) optional

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

Default value: "10m"

wait_for_elb_capacity (number) optional

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

Default value: 0

warm_pool optional

If this block is configured, add a Warm Pool to the specified Auto Scaling group. See warm_pool.

Type:

object({
pool_state                  = string
min_size                    = number
max_group_prepared_capacity = number
})

Default value: null

Context Variables

The following variables are defined in the context.tf file of this module and part of the terraform-null-label pattern.

additional_tag_map (map(string)) optional

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.

Required: No

Default value: { }

attributes (list(string)) optional

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.

Required: No

Default value: [ ]

context (any) optional

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.

Required: No

Default value:

{
  "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
}

delimiter (string) optional

Delimiter to be used between ID elements.
Defaults to - (hyphen). Set to "" to use no delimiter at all.

Required: No

Default value: null

descriptor_formats (any) optional

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).

Required: No

Default value: { }

enabled (bool) optional

Set to false to prevent the module from creating any resources
Required: No

Default value: null

environment (string) optional

ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'
Required: No

Default value: null

id_length_limit (number) optional

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.

Required: No

Default value: null

label_key_case (string) optional

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.

Required: No

Default value: null

label_order (list(string)) optional

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.

Required: No

Default value: null

label_value_case (string) optional

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.

Required: No

Default value: null

labels_as_tags (set(string)) optional

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.

Required: No

Default value:

[
  "default"
]

name (string) optional

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.

Required: No

Default value: null

namespace (string) optional

ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique
Required: No

Default value: null

regex_replace_chars (string) optional

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.

Required: No

Default value: null

stage (string) optional

ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'
Required: No

Default value: null

tags (map(string)) optional

Additional tags (e.g. {'BusinessUnit': 'XYZ'}).
Neither the tag keys nor the tag values will be modified by this module.

Required: No

Default value: { }

tenant (string) optional

ID element (Rarely used, not included by default). A customer identifier, indicating who this instance of a resource is for
Required: No

Default value: null

Outputs

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

Dependencies

Requirements

terraform, version: >= 1.3
aws, version: >= 5.16

Providers

aws, version: >= 5.16

Modules

Name	Version	Source	Description
`this`	0.25.0	`cloudposse/label/null`	n/a

Resources

The following resources are used by this module:

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)

Data Sources

The following data sources are used by this module:

aws_subnet.this (data source)

Module: ec2-autoscale-group

Usage​

Variables​

Required Variables​

Optional Variables​

Context Variables​

Outputs​

Dependencies​

Requirements​

Providers​

Modules​

Resources​

Data Sources​

Module: `ec2-autoscale-group`

Usage

Variables

Required Variables

Optional Variables

Context Variables

Outputs

Dependencies

Requirements

Providers

Modules

Resources

Data Sources