AWS Terraform module which runs Atlantis on AWS Fargate

Atlantis is tool which provides unified workflow for collaborating on Terraform through GitHub and GitLab.

This repository contains Terraform infrastructure code which creates AWS resources required to run Atlantis on AWS, including:

• Virtual Private Cloud (VPC)
• SSL certificate using Amazon Certificate Manager (ACM)
• Application Load Balancer (ALB)
• Domain name using AWS Route53 which points to ALB
• AWS Elastic Cloud Service (ECS) and AWS Fargate running Atlantis Docker image
• AWS Parameter Store to keep secrets and access them in ECS task natively

AWS Fargate is used instead of AWS ECS/EC2 to reduce the bill, and it is also a cool AWS service.

Depending on which SCM system you use, Github repositories or Gitlab projects has to be configured to post events to Atlantis webhook URL.

See README.md in examples for Github or Gitlab for complete details.

Before using Atlantis and the code in this repository please make sure that you have read and understood the security implications described in the official Atlantis documentation.

How to use this?

As often with the code published in terraform-aws-modules GitHub organization you should have everything to run this code and get Atlantis up and running.

There are three ways to do this:

1. As a standalone project
2. As a Terraform module
3. As a part of an existing AWS infrastructure

Run Atlantis as a standalone project

1. Clone this github repository:

$ git clone git@github.com:terraform-aws-modules/terraform-aws-atlantis.git
$ cd terraform-aws-atlantis

2. Copy sample terraform.tfvars.sample into terraform.tfvars and specify required variables there.

3. Run terraform init to download required providers and modules.

4. Run terraform apply to apply the Terraform configuration and create required infrastructure.

5. Run terraform output atlantis_url to get URL where Atlantis is publicly reachable. (Note: It may take a minute or two to get it reachable for the first time)

6. Github webhook is automatically created if github_token, github_organization and github_repo_names were specified. Read Add GitHub Webhook in the official Atlantis documentation or check example "GitHub repository webhook for Atlantis" to add more webhooks.

Run Atlantis as a Terraform module

This way allows integration with your existing Terraform configurations.

module "atlantis" {
  source = "terraform-aws-modules/atlantis/aws"

  name = "atlantis"

  # VPC
  cidr            = "10.20.0.0/20"
  azs             = ["eu-west-1a", "eu-west-1b", "eu-west-1c"]
  private_subnets = ["10.20.1.0/24", "10.20.2.0/24", "10.20.3.0/24"]
  public_subnets  = ["10.20.101.0/24", "10.20.102.0/24", "10.20.103.0/24"]

  # DNS (without trailing dot)
  route53_zone_name = "example.com"

  # ACM (SSL certificate) - Specify ARN of an existing certificate or new one will be created and validated using Route53 DNS
  certificate_arn = "arn:aws:acm:eu-west-1:135367859851:certificate/70e008e1-c0e1-4c7e-9670-7bb5bd4f5a84"

  # Atlantis
  atlantis_github_user       = "atlantis-bot"
  atlantis_github_user_token = "examplegithubtoken"
  atlantis_repo_whitelist    = ["github.com/terraform-aws-modules/*"]
}

Run Atlantis as a part of an existing AWS infrastructure (use existing VPC)

This way allows integration with your existing AWS resources - VPC, public and private subnets. Specify the following arguments (see methods described above):

vpc_id             = "vpc-1651acf1"
private_subnet_ids = ["subnet-1fe3d837", "subnet-129d66ab"]
public_subnet_ids  = ["subnet-1211eef5", "subnet-163466ab"]

If vpc_id is specified it will take precedence over cidr and existing VPC will be used. private_subnet_ids and public_subnet_ids must be specified also.

Make sure that both private and public subnets were created in the same set of availability zones (ALB will be created in public subnets, ECS Fargate service in private subnets).

If all provided subnets are public (no NAT gateway) then ecs_service_assign_public_ip should be set to true.

Notes

1. AWS Route53 zone is not created by this module, so zone specified as a value in route53_zone_name should be created before using this module. Check documentation for aws_route53_zone.
2. Currently this module configures Atlantis in a way that it can not be used to work with GitHub and Gitlab simultaneously (can't make list of ECS secrets conditionally).

Examples

• GitHub repository webhook for Atlantis
• GitLab repository webhook for Atlantis

Inputs

Name	Description	Type	Default	Required
acm_certificate_domain_name	Route53 domain name to use for ACM certificate. Route53 zone for this domain should be created in advance. Specify if it is different from value in route53_zone_name	string	``	no
alb_ingress_cidr_blocks	List of IPv4 CIDR ranges to use on all ingress rules of the ALB.	list	[ "0.0.0.0/0" ]	no
allow_repo_config	When true allows the use of atlantis.yaml config files within the source repos.	string	false	no
atlantis_allowed_repo_names	Github repositories where webhook should be created	list	[]	no
atlantis_github_user	GitHub username that is running the Atlantis command	string	``	no
atlantis_github_user_token	GitHub token of the user that is running the Atlantis command	string	``	no
atlantis_github_user_token_ssm_parameter_name	Name of SSM parameter to keep atlantis_github_user_token	string	/atlantis/github/user/token	no
atlantis_gitlab_user	Gitlab username that is running the Atlantis command	string	``	no
atlantis_gitlab_user_token	Gitlab token of the user that is running the Atlantis command	string	``	no
atlantis_gitlab_user_token_ssm_parameter_name	Name of SSM parameter to keep atlantis_gitlab_user_token	string	/atlantis/gitlab/user/token	no
atlantis_image	Docker image to run Atlantis with. If not specified, official Atlantis image will be used	string	``	no
atlantis_port	Local port Atlantis should be running on. Default value is most likely fine.	string	4141	no
atlantis_repo_whitelist	List of allowed repositories Atlantis can be used with	list	-	yes
atlantis_version	Verion of Atlantis to run. If not specified latest will be used	string	latest	no
azs	A list of availability zones in the region	list	[]	no
certificate_arn	ARN of certificate issued by AWS ACM. If empty, a new ACM certificate will be created and validated using Route53 DNS	string	``	no
cidr	The CIDR block for the VPC which will be created if vpc_id is not specified	string	``	no
cloudwatch_log_retention_in_days	Retention period of Atlantis CloudWatch logs	string	7	no
create_route53_record	Whether to create Route53 record for Atlantis	string	true	no
custom_container_definitions	A list of valid container definitions provided as a single valid JSON document. By default, the standard container definition is used.	string	``	no
ecs_service_assign_public_ip	Should be true, if ECS service is using public subnets (more info: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_cannot_pull_image.html)	string	false	no
ecs_service_deployment_maximum_percent	The upper limit (as a percentage of the service's desiredCount) of the number of running tasks that can be running in a service during a deployment	string	200	no
ecs_service_deployment_minimum_healthy_percent	The lower limit (as a percentage of the service's desiredCount) of the number of running tasks that must remain running and healthy in a service during a deployment	string	50	no
ecs_service_desired_count	The number of instances of the task definition to place and keep running	string	1	no
ecs_task_cpu	The number of cpu units used by the task	string	256	no
ecs_task_memory	The amount (in MiB) of memory used by the task	string	512	no
name	Name to use on all resources created (VPC, ALB, etc)	string	atlantis	no
policies_arn	A list of the ARN of the policies you want to apply	list	[ "arn:aws:iam::aws:policy/service-role/AmazonECSTaskExecutionRolePolicy" ]	no
private_subnet_ids	A list of IDs of existing private subnets inside the VPC	list	[]	no
private_subnets	A list of private subnets inside the VPC	list	[]	no
public_subnet_ids	A list of IDs of existing public subnets inside the VPC	list	[]	no
public_subnets	A list of public subnets inside the VPC	list	[]	no
route53_zone_name	Route53 zone name to create ACM certificate in and main A-record, without trailing dot	string	``	no
ssm_kms_key_arn	ARN of KMS key to use for entryption and decryption of SSM Parameters. Required only if your key uses a custom KMS key and not the default key	string	``	no
tags	A map of tags to use on all resources	map	{}	no
vpc_id	ID of an existing VPC where resources will be created	string	``	no
webhook_ssm_parameter_name	Name of SSM parameter to keep webhook secret	string	/atlantis/webhook/secret	no

Outputs

Name	Description
atlantis_allowed_repo_names	Github repositories where webhook should be created
atlantis_url	URL of Atlantis
atlantis_url_events	Webhook events URL of Atlantis
task_role_arn	The Atlantis ECS task role arn
webhook_secret	Webhook secret

Authors

Module is created and maintained by Anton Babenko.

Seth Vargo has created atlantis-on-gke(Terraform configurations for running Atlantis on Google Kubernetes Engine). This inspired me to do similar stuff for AWS Fargate.

License

Apache 2 Licensed. See LICENSE for full details.