README.md

May 29, 2025 · View on GitHub

Terraform Module for providing N general purpose EC2 hosts.

If you only need to provision a single EC2 instance, consider using the terraform-aws-ec2-instance module instead.

IMPORTANT This module by-design does not provision an AutoScaling group. It was designed to provision a discrete number of instances suitable for running stateful services such as databases (e.g. Kafka, Redis, etc).

Included features:

Automatically create a Security Group
Option to switch EIP attachment
CloudWatch monitoring and automatic reboot if instance hangs
Assume Role capability

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Usage

Note: add ${var.ssh_key_pair} private key to the ssh agent.

Include this repository as a module in your existing terraform code.

Simple example:

module "instance" {
  source = "cloudposse/ec2-instance-group/aws"
  # Cloud Posse recommends pinning every module to a specific version
  # version = "x.x.x"
  namespace                   = "eg"
  stage                       = "prod"
  name                        = "app"
  ami                         = "ami-a4dc46db"
  ami_owner                   = "099720109477"
  ssh_key_pair                = var.ssh_key_pair
  instance_type               = var.instance_type
  vpc_id                      = var.vpc_id
  security_groups             = var.security_groups
  subnet                      = var.subnet
  instance_count              = 3
}

Example with additional volumes and EIP

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

  namespace                   = "eg"
  stage                       = "prod"
  name                        = "app"
  ami                         = "ami-a4dc46db"
  ami_owner                   = "099720109477"
  ssh_key_pair                = var.ssh_key_pair
  vpc_id                      = var.vpc_id
  security_groups             = var.security_groups
  subnet                      = var.subnet
  associate_public_ip_address = true
  additional_ips_count        = 1
  ebs_volume_count            = 2
  instance_count              = 3

  security_group_rules = [
    {
      type        = "egress"
      from_port   = 0
      to_port     = 65535
      protocol    = "-1"
      cidr_blocks = ["0.0.0.0/0"]
    },
    {
      type        = "ingress"
      from_port   = 22
      to_port     = 22
      protocol    = "tcp"
      cidr_blocks = ["0.0.0.0/0"]
    },
    {
      type        = "ingress"
      from_port   = 80
      to_port     = 80
      protocol    = "tcp"
      cidr_blocks = ["0.0.0.0/0"]
    },
    {
      type        = "ingress"
      from_port   = 443
      to_port     = 443
      protocol    = "tcp"
      cidr_blocks = ["0.0.0.0/0"]
    }
  ]
}

Additional complete working example with variations of how to use the module

In /examples directory

This module depends on these modules:

terraform-terraform-label

It is necessary to run terraform get or terraform init to download this module.

Now reference the label when creating an instance (for example):

resource "aws_ami_from_instance" "example" {
  count              = length(module.instance.*.id)
  name               = "app"
  source_instance_id = element(module.instance.*.id, count.index)
}

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.

Requirements

Name	Version
terraform	>= 1.0
aws	>= 2.0

Providers

Name	Version
aws	>= 2.0

Modules

Name	Source	Version
label	cloudposse/label/null	0.25.0
security_group	cloudposse/security-group/aws	2.2.0
ssh_key_pair	cloudposse/key-pair/aws	0.19.0
this	cloudposse/label/null	0.25.0

Resources

Name	Type
aws_cloudwatch_metric_alarm.default	resource
aws_ebs_volume.default	resource
aws_eip.additional	resource
aws_eip.default	resource
aws_iam_instance_profile.default	resource
aws_iam_role.default	resource
aws_instance.default	resource
aws_network_interface.additional	resource
aws_network_interface_attachment.additional	resource
aws_volume_attachment.default	resource
aws_ami.info	data source
aws_caller_identity.default	data source
aws_iam_policy_document.default	data source
aws_region.default	data source

Inputs

Name	Description	Type	Default	Required
additional_ips_count	Count of additional EIPs	`number`	`0`	no
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
ami	The AMI to use for the instance	`string`	n/a	yes
ami_owner	Owner of the given AMI	`string`	n/a	yes
applying_period	The period in seconds over which the specified statistic is applied	`number`	`60`	no
assign_eip_address	Assign an Elastic IP address to the instance	`bool`	`true`	no
associate_public_ip_address	Associate a public IP address with the instance	`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
availability_zone	Availability Zone the instance is launched in. If not set, will be launched in the first AZ of the region	`string`	`""`	no
comparison_operator	The arithmetic operation to use when comparing the specified Statistic and Threshold. Possible values are: GreaterThanOrEqualToThreshold, GreaterThanThreshold, LessThanThreshold, LessThanOrEqualToThreshold	`string`	`"GreaterThanOrEqualToThreshold"`	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
default_alarm_action	Default alarm action	`string`	`"action/actions/AWS_EC2.InstanceId.Reboot/1.0"`	no
delete_on_termination	Whether the volume should be destroyed on instance termination	`bool`	`true`	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
disable_api_termination	Enable EC2 Instance Termination Protection	`bool`	`false`	no
ebs_device_names	Name of the EBS device to mount	`list(string)`	[ "/dev/xvdb", "/dev/xvdc", "/dev/xvdd", "/dev/xvde", "/dev/xvdf", "/dev/xvdg", "/dev/xvdh", "/dev/xvdi", "/dev/xvdj", "/dev/xvdk", "/dev/xvdl", "/dev/xvdm", "/dev/xvdn", "/dev/xvdo", "/dev/xvdp", "/dev/xvdq", "/dev/xvdr", "/dev/xvds", "/dev/xvdt", "/dev/xvdu", "/dev/xvdv", "/dev/xvdw", "/dev/xvdx", "/dev/xvdy", "/dev/xvdz" ]	no
ebs_iops	Amount of provisioned IOPS. This must be set with a volume_type of io1	`number`	`0`	no
ebs_optimized	Launched EC2 instance will be EBS-optimized	`bool`	`false`	no
ebs_volume_count	Count of EBS volumes that will be attached to the instance	`number`	`0`	no
ebs_volume_encrypted	Size of the EBS volume in gigabytes	`bool`	`true`	no
ebs_volume_size	Size of the EBS volume in gigabytes	`number`	`10`	no
ebs_volume_type	The type of EBS volume. Can be standard, gp2 or io1	`string`	`"gp2"`	no
enabled	Set to false to prevent the module from creating any resources	`bool`	`null`	no
environment	ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'	`string`	`null`	no
evaluation_periods	The number of periods over which data is compared to the specified threshold	`number`	`5`	no
generate_ssh_key_pair	If true, create a new key pair and save the pem for it to the current working directory	`bool`	`false`	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
instance_count	Count of ec2 instances to create	`number`	`1`	no
instance_type	The type of the instance	`string`	`"t2.micro"`	no
ipv6_address_count	Number of IPv6 addresses to associate with the primary network interface. Amazon EC2 chooses the IPv6 addresses from the range of your subnet	`number`	`0`	no
ipv6_addresses	List of IPv6 addresses from the range of the subnet to associate with the primary network interface	`list(string)`	`[]`	no
kms_key_id	KMS key ID used to encrypt EBS volume. When specifying kms_key_id, ebs_volume_encrypted needs to be set to true	`string`	`null`	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
metadata_http_endpoint_enabled	Whether the metadata service is available	`bool`	`true`	no
metadata_http_tokens_required	Whether or not the metadata service requires session tokens, also referred to as Instance Metadata Service Version 2.	`bool`	`true`	no
metric_name	The name for the alarm's associated metric. Allowed values can be found in https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/ec2-metricscollected.html	`string`	`"StatusCheckFailed_Instance"`	no
metric_namespace	The namespace for the alarm's associated metric. Allowed values can be found in https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/aws-namespaces.html	`string`	`"AWS/EC2"`	no
metric_threshold	The value against which the specified statistic is compared	`number`	`1`	no
monitoring	Launched EC2 instance will have detailed monitoring enabled	`bool`	`true`	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
permissions_boundary_arn	Policy ARN to attach to instance role as a permissions boundary	`string`	`""`	no
private_ips	Private IP address to associate with the instances in the VPC	`list(string)`	`[]`	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
region	AWS Region the instance is launched in	`string`	n/a	yes
root_block_device_encrypted	Whether to encrypt the root block device	`bool`	`true`	no
root_iops	Amount of provisioned IOPS. This must be set if root_volume_type is set to `io1`	`number`	`0`	no
root_volume_size	Size of the root volume in gigabytes	`number`	`10`	no
root_volume_type	Type of root volume. Can be standard, gp2 or io1	`string`	`"gp2"`	no
security_group_description	The Security Group description.	`string`	`"EC2 instances Security Group"`	no
security_group_enabled	Whether to create default Security Group for EC2 instances.	`bool`	`true`	no
security_group_name	The name to assign to the security group. Must be unique within the VPC. If not provided, will be derived from the `null-label.context` passed in. If `create_before_destroy` is true, will be used as a name prefix.	`list(string)`	`[]`	no
security_group_rules	A list of maps of Security Group rules. The values of map is fully complated with `aws_security_group_rule` resource. To get more info see https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/security_group_rule .	`list(any)`	`[]`	no
security_groups	A list of Security Group IDs to associate with EC2 instances.	`list(string)`	`[]`	no
source_dest_check	Controls if traffic is routed to the instance when the destination address does not match the instance. Used for NAT or VPNs	`bool`	`true`	no
ssh_key_pair	SSH key pair to be provisioned on the instance	`string`	`""`	no
ssh_key_pair_path	Path to where the generated key pairs will be created. Defaults to $${path.cwd}	`string`	`""`	no
stage	ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'	`string`	`null`	no
statistic_level	The statistic to apply to the alarm's associated metric. Allowed values are: SampleCount, Average, Sum, Minimum, Maximum	`string`	`"Maximum"`	no
subnet	VPC Subnet ID the instance is launched in	`string`	n/a	yes
tags	Additional tags (e.g. `{'BusinessUnit': 'XYZ'}`). Neither the tag keys nor the tag values will be modified by this module.	`map(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
user_data	Instance user data. Do not pass gzip-compressed data via this argument	`string`	`""`	no
vpc_id	The ID of the VPC that the instance security group belongs to	`string`	n/a	yes

Outputs

Name	Description
alarm_ids	CloudWatch Alarm IDs
aws_key_pair_name	Name of AWS key pair
ebs_ids	IDs of EBSs
eip_per_instance_count	Number of EIPs per instance.
eni_to_eip_map	Map of ENI with EIP
ids	Disambiguated IDs list
instance_count	Total number of instances created
name	Instance(s) name
new_ssh_keypair_generated	Was a new ssh_key_pair generated
primary_network_interface_ids	IDs of the instance's primary network interface
private_dns	Private DNS records of instances
private_ips	Private IPs of instances
public_dns	All public DNS records for the public interfaces and ENIs
public_ips	List of Public IPs of instances (or EIP)
role_names	Names of AWS IAM Roles associated with creating instance
security_group_arn	EC2 instances Security Group ARN
security_group_id	EC2 instances Security Group ID
security_group_ids	ID on the new AWS Security Group associated with creating instance
security_group_name	EC2 instances Security Group name
ssh_key_pem_path	Path where SSH key pair was created (if applicable)

Check out these related projects.

terraform-aws-ec2-instance - Terraform Module for providing a general EC2 instance provisioned by Ansible
terraform-aws-ec2-bastion-server - Terraform Module to define a generic Bastion host with parameterized user_data
https://github.com/cloudposse/terraform-aws-rds-cluster - Terraform module to provision an RDS Aurora cluster for MySQL or Postgres

References

For additional context, refer to some of these links.

terraform-aws-ec2-bastion-server - Terraform module to define a generic Bastion host with parameterized user_data

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Preamble to the Apache License, Version 2.0

Complete license is available in the LICENSE file.

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