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https://github.com/cloudposse/terraform-aws-ec2-autoscale-group

Terraform module to provision Auto Scaling Group and Launch Template on AWS
https://github.com/cloudposse/terraform-aws-ec2-autoscale-group
amazon-web-services ami asg autoscaling autoscaling-group autoscaling-policies aws cloudwatch-metric ec2 hcl2 launch template
Last synced: 3 days ago
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Terraform module to provision Auto Scaling Group and Launch Template on AWS
Host: GitHub
URL: https://github.com/cloudposse/terraform-aws-ec2-autoscale-group
Owner: cloudposse
License: apache-2.0
Created: 2018-07-07T04:03:19.000Z (over 6 years ago)
Default Branch: main
Last Pushed: 2025-01-01T03:11:45.000Z (10 days ago)
Last Synced: 2025-01-01T12:04:41.538Z (10 days ago)
Topics: amazon-web-services, ami, asg, autoscaling, autoscaling-group, autoscaling-policies, aws, cloudwatch-metric, ec2, hcl2, launch, template
Language: HCL
Homepage: https://cloudposse.com/accelerate
Size: 4.06 MB
Stars: 137
Watchers: 22
Forks: 144
Open Issues: 7
Metadata Files:
- Readme: README.md
- License: LICENSE
- Codeowners: .github/CODEOWNERS
Awesome Lists containing this project

awesome-starts - cloudposse/terraform-aws-ec2-autoscale-group - Terraform module to provision Auto Scaling Group and Launch Template on AWS (aws)
README

        




    




Terraform module to provision [Auto Scaling Group](https://www.terraform.io/docs/providers/aws/r/autoscaling_group.html) and [Launch Template](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-launch-templates.html) 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](https://github.com/cloudposse/terraform-aws-ec2-autoscale-group/issues/55).

To use a `StepScaling` or `TargetTrackingScaling` policy, create it yourself and then pass it in the `alarm_actions` field of `custom_alarms`.

> [!TIP]

> #### 👽 Use Atmos with Terraform

> Cloud Posse uses [`atmos`](https://atmos.tools) to easily orchestrate multiple environments using Terraform. 


> Works with [Github Actions](https://atmos.tools/integrations/github-actions/), [Atlantis](https://atmos.tools/integrations/atlantis), or [Spacelift](https://atmos.tools/integrations/spacelift).

>

> 

> Watch demo of using Atmos with Terraform

> 


> Example of running atmos to manage infrastructure from our Quick Start tutorial.

> 

## Usage

```hcl

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 :

```hlc

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.

> [!IMPORTANT]

> In Cloud Posse's examples, we avoid pinning modules to specific versions to prevent discrepancies between the documentation

> and the latest released versions. However, for your own projects, we strongly advise pinning each module to the exact version

> you're using. This practice ensures the stability of your infrastructure. Additionally, we recommend implementing a systematic

> approach for updating versions to avoid unexpected changes.

## Makefile Targets

```text

Available targets:

  help                                Help screen

  help/all                            Display help for all targets

  help/short                          This help short screen

  lint                                Lint terraform code

```

## Requirements

| Name | Version |

|------|---------|

|  [terraform](#requirement\_terraform) | >= 1.3 |

|  [aws](#requirement\_aws) | >= 5.16 |

## Providers

| Name | Version |

|------|---------|

|  [aws](#provider\_aws) | >= 5.16 |

## Modules

| Name | Source | Version |

|------|--------|---------|

|  [this](#module\_this) | cloudposse/label/null | 0.25.0 |

## Resources

| Name | Type |

|------|------|

| [aws_autoscaling_group.default](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/autoscaling_group) | resource |

| [aws_autoscaling_policy.scale_down](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/autoscaling_policy) | resource |

| [aws_autoscaling_policy.scale_up](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/autoscaling_policy) | resource |

| [aws_cloudwatch_metric_alarm.all_alarms](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/cloudwatch_metric_alarm) | resource |

| [aws_launch_template.default](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/launch_template) | resource |

| [aws_subnet.this](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/subnet) | data source |

## Inputs

| Name | Description | Type | Default | Required |

|------|-------------|------|---------|:--------:|

|  [additional\_tag\_map](#input\_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](#input\_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](#input\_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](#input\_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](#input\_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](#input\_capacity\_rebalance) | Indicates whether capacity rebalance is enabled. Otherwise, capacity rebalance is disabled. | `bool` | `false` | no |

|  [context](#input\_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](#input\_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](#input\_cpu\_utilization\_high\_period\_seconds) | The period in seconds over which the specified statistic is applied | `number` | `300` | no |

|  [cpu\_utilization\_high\_statistic](#input\_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](#input\_cpu\_utilization\_high\_threshold\_percent) | The value against which the specified statistic is compared | `number` | `90` | no |

|  [cpu\_utilization\_low\_evaluation\_periods](#input\_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](#input\_cpu\_utilization\_low\_period\_seconds) | The period in seconds over which the specified statistic is applied | `number` | `300` | no |

|  [cpu\_utilization\_low\_statistic](#input\_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](#input\_cpu\_utilization\_low\_threshold\_percent) | The value against which the specified statistic is compared | `number` | `10` | no |

|  [credit\_specification](#input\_credit\_specification) | Customize the credit specification of the instances | object({
    cpu_credits = string
  }) | `null` | no |

|  [custom\_alarms](#input\_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](#input\_default\_alarms\_enabled) | Enable or disable cpu and memory Cloudwatch alarms | `bool` | `true` | no |

|  [default\_cooldown](#input\_default\_cooldown) | The amount of time, in seconds, after a scaling activity completes before another scaling activity can start | `number` | `300` | no |

|  [delimiter](#input\_delimiter) | Delimiter to be used between ID elements.
Defaults to `-` (hyphen). Set to `""` to use no delimiter at all. | `string` | `null` | no |

|  [descriptor\_formats](#input\_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
`{
   format = string
   labels = list(string)
}`
(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](#input\_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](#input\_disable\_api\_termination) | If `true`, enables EC2 Instance Termination Protection | `bool` | `false` | no |

|  [ebs\_optimized](#input\_ebs\_optimized) | If true, the launched EC2 instance will be EBS-optimized | `bool` | `false` | no |

|  [elastic\_gpu\_specifications](#input\_elastic\_gpu\_specifications) | Specifications of Elastic GPU to attach to the instances | object({
    type = string
  }) | `null` | no |

|  [enable\_monitoring](#input\_enable\_monitoring) | Enable/disable detailed monitoring | `bool` | `true` | no |

|  [enabled](#input\_enabled) | Set to false to prevent the module from creating any resources | `bool` | `null` | no |

|  [enabled\_metrics](#input\_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](#input\_environment) | ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT' | `string` | `null` | no |

|  [force\_delete](#input\_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](#input\_health\_check\_grace\_period) | Time (in seconds) after instance comes into service before checking health | `number` | `300` | no |

|  [health\_check\_type](#input\_health\_check\_type) | Controls how health checking is done. Valid values are `EC2` or `ELB` | `string` | `"EC2"` | no |

|  [iam\_instance\_profile\_name](#input\_iam\_instance\_profile\_name) | The IAM instance profile name to associate with launched instances | `string` | `""` | no |

|  [id\_length\_limit](#input\_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](#input\_image\_id) | The EC2 image ID to launch | `string` | `""` | no |

|  [instance\_initiated\_shutdown\_behavior](#input\_instance\_initiated\_shutdown\_behavior) | Shutdown behavior for the instances. Can be `stop` or `terminate` | `string` | `"terminate"` | no |

|  [instance\_market\_options](#input\_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](#input\_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](#input\_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](#input\_instance\_type) | Instance type to launch | `string` | n/a | yes |

|  [key\_name](#input\_key\_name) | The SSH key name that should be used for the instance | `string` | `""` | no |

|  [label\_key\_case](#input\_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](#input\_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](#input\_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](#input\_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](#input\_launch\_template\_version) | Launch template version. Can be version number, `$Latest` or `$Default` | `string` | `"$Latest"` | no |

|  [load\_balancers](#input\_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](#input\_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](#input\_max\_size) | The maximum size of the autoscale group | `number` | n/a | yes |

|  [metadata\_http\_endpoint\_enabled](#input\_metadata\_http\_endpoint\_enabled) | Set false to disable the Instance Metadata Service. | `bool` | `true` | no |

|  [metadata\_http\_protocol\_ipv6\_enabled](#input\_metadata\_http\_protocol\_ipv6\_enabled) | Set true to enable IPv6 in the launch template. | `bool` | `false` | no |

|  [metadata\_http\_put\_response\_hop\_limit](#input\_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](#input\_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](#input\_metadata\_instance\_metadata\_tags\_enabled) | Set true to enable metadata tags in the launch template. | `bool` | `false` | no |

|  [metrics\_granularity](#input\_metrics\_granularity) | The granularity to associate with the metrics to collect. The only valid value is 1Minute | `string` | `"1Minute"` | no |

|  [min\_elb\_capacity](#input\_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](#input\_min\_size) | The minimum size of the autoscale group | `number` | n/a | yes |

|  [mixed\_instances\_policy](#input\_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](#input\_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](#input\_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](#input\_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](#input\_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](#input\_placement\_group) | The name of the placement group into which you'll launch your instances, if any | `string` | `""` | no |

|  [protect\_from\_scale\_in](#input\_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](#input\_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](#input\_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](#input\_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](#input\_scale\_down\_policy\_type) | The scaling policy type. Currently only `SimpleScaling` is supported | `string` | `"SimpleScaling"` | no |

|  [scale\_down\_scaling\_adjustment](#input\_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](#input\_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](#input\_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](#input\_scale\_up\_policy\_type) | The scaling policy type. Currently only `SimpleScaling` is supported | `string` | `"SimpleScaling"` | no |

|  [scale\_up\_scaling\_adjustment](#input\_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](#input\_security\_group\_ids) | A list of associated security group IDs | `list(string)` | `[]` | no |

|  [service\_linked\_role\_arn](#input\_service\_linked\_role\_arn) | The ARN of the service-linked role that the ASG will use to call other AWS services | `string` | `""` | no |

|  [stage](#input\_stage) | ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release' | `string` | `null` | no |

|  [subnet\_ids](#input\_subnet\_ids) | A list of subnet IDs to launch resources in | `list(string)` | n/a | yes |

|  [suspended\_processes](#input\_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](#input\_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](#input\_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](#input\_target\_group\_arns) | A list of aws\_alb\_target\_group ARNs, for use with Application Load Balancing | `list(string)` | `[]` | no |

|  [tenant](#input\_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](#input\_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](#input\_update\_default\_version) | Whether to update Default version of Launch template each update | `bool` | `false` | no |

|  [user\_data\_base64](#input\_user\_data\_base64) | The Base64-encoded user data to provide when launching the instances | `string` | `""` | no |

|  [wait\_for\_capacity\_timeout](#input\_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](#input\_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](#input\_warm\_pool) | If this block is configured, add a Warm Pool to the specified Auto Scaling group. See [warm\_pool](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/autoscaling_group#warm_pool). | object({
    pool_state                  = string
    min_size                    = number
    max_group_prepared_capacity = number
  })
 | `null` | no |

## Outputs

| Name | Description |

|------|-------------|

|  [autoscaling\_group\_arn](#output\_autoscaling\_group\_arn) | ARN of the AutoScaling Group |

|  [autoscaling\_group\_default\_cooldown](#output\_autoscaling\_group\_default\_cooldown) | Time between a scaling activity and the succeeding scaling activity |

|  [autoscaling\_group\_desired\_capacity](#output\_autoscaling\_group\_desired\_capacity) | The number of Amazon EC2 instances that should be running in the group |

|  [autoscaling\_group\_health\_check\_grace\_period](#output\_autoscaling\_group\_health\_check\_grace\_period) | Time after instance comes into service before checking health |

|  [autoscaling\_group\_health\_check\_type](#output\_autoscaling\_group\_health\_check\_type) | `EC2` or `ELB`. Controls how health checking is done |

|  [autoscaling\_group\_id](#output\_autoscaling\_group\_id) | The AutoScaling Group id |

|  [autoscaling\_group\_max\_size](#output\_autoscaling\_group\_max\_size) | The maximum size of the autoscale group |

|  [autoscaling\_group\_min\_size](#output\_autoscaling\_group\_min\_size) | The minimum size of the autoscale group |

|  [autoscaling\_group\_name](#output\_autoscaling\_group\_name) | The AutoScaling Group name |

|  [autoscaling\_group\_tags](#output\_autoscaling\_group\_tags) | A list of tag settings associated with the AutoScaling Group |

|  [autoscaling\_policy\_scale\_down\_arn](#output\_autoscaling\_policy\_scale\_down\_arn) | ARN of the AutoScaling policy scale down |

|  [autoscaling\_policy\_scale\_up\_arn](#output\_autoscaling\_policy\_scale\_up\_arn) | ARN of the AutoScaling policy scale up |

|  [launch\_template\_arn](#output\_launch\_template\_arn) | The ARN of the launch template |

|  [launch\_template\_id](#output\_launch\_template\_id) | The ID of the launch template |

## Related Projects

Check out these related projects.

- [terraform-aws-ec2-instance](https://github.com/cloudposse/terraform-aws-ec2-instance) - Terraform module for providing a general purpose EC2 instance

- [terraform-aws-ec2-bastion-server](https://github.com/cloudposse/terraform-aws-ec2-bastion-server) - Terraform module to define a generic bastion host with parameterized user data

- [terraform-aws-ec2-admin-server](https://github.com/cloudposse/terraform-aws-ec2-admin-server) - Terraform module for providing an EC2 instance capable of running admin tasks

- [terraform-aws-ec2-instance-group](https://github.com/cloudposse/terraform-aws-ec2-instance-group) - Terraform module for provisioning multiple general purpose EC2 hosts for stateful applications

- [terraform-aws-ec2-ami-snapshot](https://github.com/cloudposse/terraform-aws-ec2-ami-snapshot) - Terraform module to easily generate AMI snapshots to create replica instances

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## ✨ Contributing

This project is under active development, and we encourage contributions from our community.

Many thanks to our outstanding contributors:



  



For 🐛 bug reports & feature requests, please use the [issue tracker](https://github.com/cloudposse/terraform-aws-ec2-autoscale-group/issues).

In general, PRs are welcome. We follow the typical "fork-and-pull" Git workflow.

 1. Review our [Code of Conduct](https://github.com/cloudposse/terraform-aws-ec2-autoscale-group/?tab=coc-ov-file#code-of-conduct) and [Contributor Guidelines](https://github.com/cloudposse/.github/blob/main/CONTRIBUTING.md).

 2. **Fork** the repo on GitHub

 3. **Clone** the project to your own machine

 4. **Commit** changes to your own branch

 5. **Push** your work back up to your fork

 6. Submit a **Pull Request** so that we can review your changes

**NOTE:** Be sure to merge the latest changes from "upstream" before making a pull request!

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## License



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Complete license is available in the [`LICENSE`](LICENSE) file.

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specific language governing permissions and limitations

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```

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