Terraform module that creates an ECS service with the following features

• Runs an ECS service with or without an AWS load balancer.
• Stream logs to a CloudWatch log group encrypted with a KMS key.
• Associate multiple target groups with Network Load Balancers (NLB) and Application Load Balancers (ALB).
• Supports running ECS tasks on EC2 instances or Fargate.

Default container definition (hello world app)

We create an initial task definition using the golang:alpine image as a way to validate the initial infrastructure is working: visiting the site shows a simple Go hello world page listening on two configurable ports. This is meant to get a proof of concept instance up and running and to help with testing.

If you want to customize the listener ports for the hello world app, you can modify the hello_world_container_ports variable.

In production usage, we expect deployment tooling to manage the container definitions going forward, not Terraform.

Terraform Versions

Terraform 0.13 and 0.14. Pin module version to ~> 6.0. Submit pull-requests to master branch.

Terraform 0.12 is deprecated.

Usage

ECS service associated with an Application Load Balancer (ALB)

module "app_ecs_service" {
  source = "trussworks/ecs-service/aws"

  name        = "app"
  environment = "prod"

  ecs_cluster                   = aws_ecs_cluster.mycluster
  ecs_vpc_id                    = module.vpc.vpc_id
  ecs_subnet_ids                = module.vpc.private_subnets
  kms_key_id                    = aws_kms_key.main.arn
  tasks_desired_count           = 2

  associate_alb      = true
  alb_security_group = module.security_group.id
  lb_target_groups =
  [
    {
      container_port              = 8443
      container_health_check_port = 8443
      lb_target_group_arn         = module.alb.arn
    }
  ]
}

ECS Service associated with a Network Load Balancer(NLB)

module "app_ecs_service" {
  source = "trussworks/ecs-service/aws"

  name        = "app"
  environment = "prod"

  ecs_cluster                   = aws_ecs_cluster.mycluster
  ecs_vpc_id                    = module.vpc.vpc_id
  ecs_subnet_ids                = module.vpc.private_subnets
  kms_key_id                    = aws_kms_key.main.arn
  tasks_desired_count           = 2

  associate_nlb          = true
  nlb_subnet_cidr_blocks = ["10.0.0.0/24", "10.0.1.0/24", "10.0.2.0/24"]

  lb_target_groups =
  [
    {
      container_port              = 8443
      container_health_check_port = 8080
      lb_target_group_arn         = module.nlb.arn
    }
  ]
}

ECS Service without any AWS load balancer

module "app_ecs_service" {
  source = "trussworks/ecs-service/aws"

  name        = "app"
  environment = "prod"

  ecs_cluster                   = aws_ecs_cluster.mycluster
  ecs_vpc_id                    = module.vpc.vpc_id
  ecs_subnet_ids                = module.vpc.private_subnets
  kms_key_id                    = aws_kms_key.main.arn
}

Requirements

Name	Version
terraform	>= 0.13
aws	>= 3.34

Providers

Name	Version
aws	5.3.0

Modules

No modules.

Resources

Name	Type
aws_cloudwatch_log_group.main	resource
aws_cloudwatch_metric_alarm.alarm_cpu	resource
aws_cloudwatch_metric_alarm.alarm_mem	resource
aws_ecs_service.main	resource
aws_ecs_task_definition.main	resource
aws_iam_policy.task_role_ecs_exec	resource
aws_iam_role.task_execution_role	resource
aws_iam_role.task_role	resource
aws_iam_role_policy.instance_role_policy	resource
aws_iam_role_policy.task_execution_role_policy	resource
aws_iam_role_policy_attachment.task_role_ecs_exec	resource
aws_security_group.ecs_sg	resource
aws_security_group_rule.app_ecs_allow_health_check_from_alb	resource
aws_security_group_rule.app_ecs_allow_health_check_from_nlb	resource
aws_security_group_rule.app_ecs_allow_https_from_alb	resource
aws_security_group_rule.app_ecs_allow_outbound	resource
aws_security_group_rule.app_ecs_allow_tcp_from_nlb	resource
aws_ecs_task_definition.main	data source
aws_iam_policy_document.ecs_assume_role_policy	data source
aws_iam_policy_document.instance_role_policy_doc	data source
aws_iam_policy_document.task_execution_role_policy_doc	data source
aws_iam_policy_document.task_role_ecs_exec	data source
aws_region.current	data source

Inputs

Name	Description	Type	Default	Required
additional_security_group_ids	In addition to the security group created for the service, a list of security groups the ECS service should also be added to.	list(string)	[]	no
alb_security_group	Application Load Balancer (ALB) security group ID to allow traffic from.	string	""	no
assign_public_ip	Whether this instance should be accessible from the public internet. Default is false.	bool	false	no
associate_alb	Whether to associate an Application Load Balancer (ALB) with the ECS service.	bool	false	no
associate_nlb	Whether to associate a Network Load Balancer (NLB) with the ECS service.	bool	false	no
cloudwatch_alarm_actions	The list of actions to take for cloudwatch alarms	list(string)	[]	no
cloudwatch_alarm_cpu_enable	Enable the CPU Utilization CloudWatch metric alarm	bool	true	no
cloudwatch_alarm_cpu_threshold	The CPU Utilization threshold for the CloudWatch metric alarm	number	80	no
cloudwatch_alarm_mem_enable	Enable the Memory Utilization CloudWatch metric alarm	bool	true	no
cloudwatch_alarm_mem_threshold	The Memory Utilization threshold for the CloudWatch metric alarm	number	80	no
cloudwatch_alarm_name	Generic name used for CPU and Memory Cloudwatch Alarms	string	""	no
container_definitions	Container definitions provided as valid JSON document. Default uses golang:alpine running a simple hello world.	string	""	no
container_image	The image of the container.	string	"golang:alpine"	no
container_volumes	Volumes that containers in your task may use.	list( object({ name = string }) )	[]	no
ec2_create_task_execution_role	Set to true to create ecs task execution role to ECS EC2 Tasks.	bool	false	no
ecr_repo_arns	The ARNs of the ECR repos. By default, allows all repositories.	list(string)	[ "*" ]	no
ecs_cluster	ECS cluster object for this task.	object({ arn = string name = string })	n/a	yes
ecs_exec_enable	Enable the ability to execute commands on the containers via Amazon ECS Exec	bool	false	no
ecs_instance_role	The name of the ECS instance role.	string	""	no
ecs_subnet_ids	Subnet IDs for the ECS tasks.	list(string)	n/a	yes
ecs_use_fargate	Whether to use Fargate for the task definition.	bool	false	no
ecs_vpc_id	VPC ID to be used by ECS.	string	n/a	yes
environment	Environment tag, e.g prod.	string	n/a	yes
ephemeral_storage_size_in_gib	The size of the ephemeral storage volume. Without explicit configuration, Amazon ECS tasks that are hosted on Fargate using platform version 1.4.0 or later receive a minimum of 20 GiB of ephemeral storage. This value can be configured from a minimum of 21 GiB up to a maximum of 200 GiB.	number	null	no
fargate_platform_version	The platform version on which to run your service. Only applicable when using Fargate launch type.	string	"LATEST"	no
fargate_task_cpu	Number of cpu units used in initial task definition. Default is minimum.	number	256	no
fargate_task_memory	Amount (in MiB) of memory used in initial task definition. Default is minimum.	number	512	no
health_check_grace_period_seconds	Grace period within which failed health checks will be ignored at container start. Only applies to services with an attached loadbalancer.	number	null	no
hello_world_container_ports	List of ports for the hello world container app to listen on. The app currently supports listening on two ports.	list(number)	[ 8080, 8081 ]	no
kms_key_id	KMS customer managed key (CMK) ARN for encrypting application logs.	string	n/a	yes
lb_target_groups	List of load balancer target group objects containing the lb_target_group_arn, container_port and container_health_check_port. The container_port is the port on which the container will receive traffic. The container_health_check_port is an additional port on which the container can receive a health check. The lb_target_group_arn is either Application Load Balancer (ALB) or Network Load Balancer (NLB) target group ARN tasks will register with.	list( object({ container_port = number container_health_check_port = number lb_target_group_arn = string } ) )	[]	no
logs_cloudwatch_group	CloudWatch log group to create and use. Default: /ecs/{name}-{environment}	string	""	no
logs_cloudwatch_retention	Number of days you want to retain log events in the log group.	number	90	no
manage_ecs_security_group	Enable creation and management of the ECS security group and rules	bool	true	no
name	The service name.	string	n/a	yes
nlb_subnet_cidr_blocks	List of Network Load Balancer (NLB) CIDR blocks to allow traffic from.	list(string)	[]	no
service_registries	List of service registry objects as per https://www.terraform.io/docs/providers/aws/r/ecs_service.html#service_registries-1. List can only have a single object until hashicorp/terraform-provider-aws#9573 is resolved.	list(object({ registry_arn = string container_name = string container_port = number port = number }))	[]	no
target_container_name	Name of the container the Load Balancer should target. Default: {name}-{environment}	string	""	no
task_definition_tags	Tags to apply to the task definition	map(string)	{}	no
tasks_desired_count	The number of instances of a task definition.	number	1	no
tasks_maximum_percent	Upper limit on the number of running tasks.	number	200	no
tasks_minimum_healthy_percent	Lower limit on the number of running tasks.	number	100	no

Outputs

Name	Description
awslogs_group	Name of the CloudWatch Logs log group containers should use.
awslogs_group_arn	ARN of the CloudWatch Logs log group containers should use.
ecs_security_group_id	Security Group ID assigned to the ECS tasks.
ecs_service_id	ARN of the ECS service.
task_definition_arn	Full ARN of the Task Definition (including both family and revision).
task_definition_family	The family of the Task Definition.
task_execution_role	The role object of the task execution role that the Amazon ECS container agent and the Docker daemon can assume.
task_execution_role_arn	The ARN of the task execution role that the Amazon ECS container agent and the Docker daemon can assume.
task_execution_role_name	The name of the task execution role that the Amazon ECS container agent and the Docker daemon can assume.
task_role	The IAM role object assumed by Amazon ECS container tasks.
task_role_arn	The ARN of the IAM role assumed by Amazon ECS container tasks.
task_role_name	The name of the IAM role assumed by Amazon ECS container tasks.

Upgrade Path

5.x.x to 6.0.0

In versions 5.x.x and prior, the following resources existed as arrays (toggled by a count meta-argument). With 6.0.0, each pair has been merged into a single resource.

• aws_cloudwatch_metric_alarm.alarm_cpu[0] xor aws_cloudwatch_metric_alarm.alarm_cpu_no_lb[0] -> aws_cloudwatch_metric_alarm.alarm_cpu
• aws_cloudwatch_metric_alarm.alarm_mem[0] xor aws_cloudwatch_metric_alarm.alarm_mem_no_lb[0] -> aws_cloudwatch_metric_alarm.alarm_mem
• aws_ecs_service.main[0] xor aws_ecs_service.main_no_lb[0] -> aws_ecs_service.main

To upgrade to 6.0.0, you will need to perform a terraform state mv for any affected resources to avoid destruction and recreation. Alternatively, you can let Terraform delete/recreate the deployed resources.

For example, if you are using this module and naming it example, you could run one or more of the commands as appropriate given your environment:

# Example alarm_cpu state mv commands (pick the relevant one for your environment):
terraform state mv 'module.example.aws_cloudwatch_metric_alarm.alarm_cpu[0]' 'module.example.aws_cloudwatch_metric_alarm.alarm_cpu'
terraform state mv 'module.example.aws_cloudwatch_metric_alarm.alarm_cpu_no_lb[0]' 'module.example.aws_cloudwatch_metric_alarm.alarm_cpu'

# Example alarm_mem state mv commands (pick the relevant one for your environment):
terraform state mv 'module.example.aws_cloudwatch_metric_alarm.alarm_mem[0]' 'module.example.aws_cloudwatch_metric_alarm.alarm_mem'
terraform state mv 'module.example.aws_cloudwatch_metric_alarm.alarm_mem_no_lb[0]' 'module.example.aws_cloudwatch_metric_alarm.alarm_mem'

# Example main state mv commands (pick the relevant one for your environment):
terraform state mv 'module.example.aws_ecs_service.main[0]' 'module.example.aws_ecs_service.main'
terraform state mv 'module.example.aws_ecs_service.main_no_lb[0]' 'module.example.aws_ecs_service.main'

5.x.x to 5.1.1

With 5.1.1, the hashicorp/aws provider must be a minimum version of 3.0. It no longer has a maximum version. Therefore any code calling this will need to accomodate for that minimum version change.

4.0.0 to 5.0.0

Prior to 5.x, the hashicorp/aws provider required the use of version 2.70. 5.x changes the hashicorp/aws provider so that it can be greater than or equal to 2.70, but must be less than 4.0. Therefore any code calling this will need to accomodate for that version change.

3.x.x to 4.0.0

3.x.x uses Terraform 0.12.x and 4.0.0 uses Terraform 0.13.x, so this requires upgrading any code that uses this module to Terraform 0.13.x.

2.x.x to 3.0.0

In 3.0.0 the module added support for multiple load balancer target groups. To support this change, container_port, container_health_check_port and lb_target_group are being replaced with lb_target_groups.

Without a load balancer

If you are using this module without an ALB or NLB then you can remove any references to container_port, container_health_check_port and lb_target_group if you were doing so.

Using with ALB or NLB target groups

If you are using an NLB or NLB target groups with this module then you will need replace the values of container_port, container_health_check_port and lb_target_group with

Below is an example of how the module would be instantiated prior to version 3.0.0:

module "app_ecs_service" {
  source = "trussworks/ecs-service/aws"
  ...
  container_port                  = 8443
  container_health_check_port     = 8080
  lb_target_group_arn             = module.alb.arn
  ...
}

In 3.0.0 the same example will look like the following

module "app_ecs_service" {
  source = "trussworks/ecs-service/aws"
  ...
  lb_target_groups =
  [
    {
      container_port                  = 8443
      container_health_check_port     = 8080
      lb_target_group_arn             = module.alb.arn
    }
  ]
  ...
}

2.0.0 to 2.1.0

In 2.1.0 KMS log encryption is required by default. This requires that you create and attach a new AWS KMS key ARN. As an example here is how to set that up (please review on your own):

data "aws_iam_policy_document" "cloudwatch_logs_allow_kms" {
  statement {
    sid    = "Enable IAM User Permissions"
    effect = "Allow"

    principals {
      type = "AWS"
      identifiers = [
        "arn:aws:iam::${data.aws_caller_identity.current.account_id}:root",
      ]
    }

    actions = [
      "kms:*",
    ]
    resources = ["*"]
  }

  statement {
    sid    = "Allow logs KMS access"
    effect = "Allow"

    principals {
      type        = "Service"
      identifiers = ["logs.us-west-2.amazonaws.com"]
    }

    actions = [
      "kms:Encrypt*",
      "kms:Decrypt*",
      "kms:ReEncrypt*",
      "kms:GenerateDataKey*",
      "kms:Describe*"
    ]
    resources = ["*"]
  }
}

resource "aws_kms_key" "main" {
  description         = "Key for ECS log encryption"
  enable_key_rotation = true

  policy = data.aws_iam_policy_document.cloudwatch_logs_allow_kms.json
}

NOTE: Best practice is to use a separate KMS key per ECS Service. Do not re-use KMS keys if it can be avoided.

1.15.0 to 2.0.0

v2.0.0 of this module is built against Terraform v0.12. In addition to requiring this upgrade, the v1.15.0 version of the module took the name of the ECS cluster as a parameter; v2.0.0 takes the actual object of the ECS cluster as a parameter instead. You will need to update previous instances of this module with the altered parameter.

Developer Setup

Install dependencies (macOS)

brew install pre-commit go terraform terraform-docs

Testing

Terratest is being used for automated testing with this module. Tests in the test folder can be run locally by running the following command:

make test

Or with aws-vault:

AWS_VAULT_KEYCHAIN_NAME=<NAME> aws-vault exec <PROFILE> -- make test