Terraform AWS ECS Service

A Terraform module for deploying an ECS service in AWS.

The ECS service requires:

• An existing VPC containing an ECS cluster
• A service role ARN allowing ECS to manage load balancers
• An ELB for the service
• A CloudWatch log group

The ECS service consists of:

• An ECS task definition for the containers making up the service
• An ECS service to maintain a number of instances of the task
• Log collection via the provided CloudWatch log group

Usage

To use the module, include something like the following in your Terraform configuration:

module "ecs_service" {
  source = "infrablocks/ecs-service/aws"
  version = "2.0.0"
  
  vpc_id = "vpc-fb7dc365"
  
  component = "important-component"
  deployment_identifier = "production"
  
  service_name = "web-app"
  service_image = "images/web-app:0.3.1"
  service_port = "8000"
  service_command = "[\"node\", \"server.js\"]"
  
  service_desired_count = "3"
  service_deployment_maximum_percent = "50"
  service_deployment_minimum_healthy_percent = "200"
  
  service_elb_name = "elb-service-web-app"
  
  service_role = "arn:aws:iam::151388205202:role/service-task-role"
  
  service_volumes = [
    {
      name = "data"
    }
  ]
  
  ecs_cluster_id = "arn:aws:ecs:eu-west-2:151388205202:cluster/web-app"
  ecs_cluster_service_role_arn = "arn:aws:iam::151388205202:role/cluster-service-role-web-app"
}

By default, the module will use the provided region, log group, service name, image, port and command to build a suitable task definition.

If further configuration of the task definition is required, provide the task definition content using the var service_task_definition. In this case, service_image and service_command need not be provided.

As mentioned above, the ECS service deploys into an existing base network and ECS cluster using an existing ELB. Whilst these can be created using any mechanism you like, the following modules may be of use:

• AWS Base Networking
• AWS ECS Cluster
• AWS ECS Load Balancer

See the Terraform registry entry for more details.

Inputs

Name	Description	Default	Required
region	The region into which to deploy the service	-	yes
vpc_id	The ID of the VPC into which to deploy the service	-	yes
component	The component this service will contain	-	yes
deployment_identifier	An identifier for this instantiation	-	yes
service_task_container_definitions	A template for the container definitions in the task	see container-definitions	no
service_name	The name of the service being created	-	yes
service_image	The docker image (including version) to deploy	-	no
service_command	The command to run to start the container	[]	no
service_port	The port the containers will be listening on	-	yes
service_task_network_mode	The network mode used for the containers in the task	bridge	yes
service_desired_count	The desired number of tasks in the service	3	yes
service_deployment_maximum_percent	The maximum percentage of the desired count that can be running	200	yes
service_deployment_minimum_healthy_percent	The minimum healthy percentage of the desired count to keep running	50	yes
scheduling_strategy	The scheduling strategy to use for the service ("REPLICA" or "DAEMON")	"REPLICA"	yes
attach_to_load_balancer	Whether or not this service should attach to a load balancer ("yes" or "no")	"yes"	yes
service_elb_name	The name of the ELB to configure to point at the service containers	-	if attach_to_load_balancer is yes and target_group_arn is not specified
target_group_arn	The ARN of the ALB's target group to point at the service containers	-	if attach_to_load_balancer is yes and service_elb_name is not specified
service_role	The ARN of the service task role to use	No task role	yes
service_volumes	A list of volumes to make available to the containers in the service	[]	yes
ecs_cluster_id	The ID of the ECS cluster in which to deploy the service	-	yes
ecs_cluster_service_role_arn	The ARN of the IAM role to provide to ECS to manage the service	-	yes

Outputs

Name	Description
task_definition_arn	The ARN of the created ECS task definition
log_group	The name of the log group capturing all task output

Compatibility

This module is compatible with Terraform versions greater than or equal to Terraform 1.0.

Development

Machine Requirements

In order for the build to run correctly, a few tools will need to be installed on your development machine:

• Ruby (3.1.1)
• Bundler
• git
• git-crypt
• gnupg
• direnv
• aws-vault

Mac OS X Setup

Installing the required tools is best managed by homebrew.

To install homebrew:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Then, to install the required tools:

# ruby
brew install rbenv
brew install ruby-build
echo 'eval "$(rbenv init - bash)"' >> ~/.bash_profile
echo 'eval "$(rbenv init - zsh)"' >> ~/.zshrc
eval "$(rbenv init -)"
rbenv install 3.1.1
rbenv rehash
rbenv local 3.1.1
gem install bundler

# git, git-crypt, gnupg
brew install git
brew install git-crypt
brew install gnupg

# aws-vault
brew cask install

# direnv
brew install direnv
echo "$(direnv hook bash)" >> ~/.bash_profile
echo "$(direnv hook zsh)" >> ~/.zshrc
eval "$(direnv hook $SHELL)"

direnv allow <repository-directory>

Running the build

Running the build requires an AWS account and AWS credentials. You are free to configure credentials however you like as long as an access key ID and secret access key are available. These instructions utilise aws-vault which makes credential management easy and secure.

To provision module infrastructure, run tests and then destroy that infrastructure, execute:

aws-vault exec <profile> -- ./go

To provision the module prerequisites:

aws-vault exec <profile> -- ./go deployment:prerequisites:provision[<deployment_identifier>]

To provision the module contents:

aws-vault exec <profile> -- ./go deployment:root:provision[<deployment_identifier>]

To destroy the module contents:

aws-vault exec <profile> -- ./go deployment:root:destroy[<deployment_identifier>]

To destroy the module prerequisites:

aws-vault exec <profile> -- ./go deployment:prerequisites:destroy[<deployment_identifier>]

Configuration parameters can be overridden via environment variables:

DEPLOYMENT_IDENTIFIER=testing aws-vault exec <profile> -- ./go

Common Tasks

Generating an SSH key pair

To generate an SSH key pair:

ssh-keygen -m PEM -t rsa -b 4096 -C [email protected] -N '' -f config/secrets/keys/bastion/ssh

Generating a self-signed certificate

To generate a self signed certificate:

openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365

To decrypt the resulting key:

openssl rsa -in key.pem -out ssl.key

Managing CircleCI keys

To encrypt a GPG key for use by CircleCI:

openssl aes-256-cbc \
  -e \
  -md sha1 \
  -in ./config/secrets/ci/gpg.private \
  -out ./.circleci/gpg.private.enc \
  -k "<passphrase>"

To check decryption is working correctly:

openssl aes-256-cbc \
  -d \
  -md sha1 \
  -in ./.circleci/gpg.private.enc \
  -k "<passphrase>"

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/infrablocks/terraform-aws-ecs-service. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The library is available as open source under the terms of the MIT License.