Terraform AWS ECS Cluster

A Terraform module for building an ECS Cluster in AWS.

The ECS cluster requires:

• An existing VPC
• Some existing subnets

The ECS cluster consists of:

• A cluster in ECS
• A launch template and auto-scaling group for a cluster of ECS container instances
• An SSH key to connect to the ECS container instances
• A security group for the container instances optionally allowing:
  • Outbound internet access for all containers
  • Inbound TCP access on any port from the VPC network
• An IAM role and policy for the container instances allowing:
  • ECS interactions
  • ECR image pulls
  • S3 object fetches
  • Logging to cloudwatch
• An IAM role and policy for ECS services allowing:
  • Elastic load balancer registration / deregistration
  • EC2 describe actions and security group ingress rule creation
• A CloudWatch log group

Usage

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

module "ecs_cluster" {
  source = "infrablocks/ecs-cluster/aws"
  version = "5.0.0"

  region = "eu-west-2"
  vpc_id = "vpc-fb7dc365"
  subnet_ids = [
   "subnet-eb32c271",
   "subnet-64872d1f"
  ]

  component = "important-component"
  deployment_identifier = "production"
  
  cluster_name = "services"
  cluster_instance_ssh_public_key_path = "~/.ssh/id_rsa.pub"
  cluster_instance_type = "t3.small"
  
  cluster_minimum_size = 2
  cluster_maximum_size = 10
  cluster_desired_capacity = 4
}

As mentioned above, the ECS cluster deploys into an existing base network. Whilst the base network can be created using any mechanism you like, the AWS Base Networking module will create everything you need. See the docs for usage instructions.

See the Terraform registry entry for more details.

Inputs

Notes:

• By default, the latest available Amazon Linux 2 AMI is used.
• For Amazon Linux 1 AMIs use version <= 0.6.0 of this module for terraform 0.11 or version = 1.0.0 for terraform 0.12.
• When a specific AMI is provided via cluster_instance_amis (a map of region to AMI ID), only the root block device can be customised, using the cluster_instance_root_block_device_size and cluster_instance_root_block_device_type variables.
• The user data template will get the cluster name as cluster_name. If none is supplied, a default will be used.

Outputs

Compatibility

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

Required Permissions

• iam:GetPolicy
• iam:GetPolicyVersion
• iam:ListPolicyVersions
• iam:ListEntitiesForPolicy
• iam:CreatePolicy
• iam:DeletePolicy
• iam:GetRole
• iam:PassRole
• iam:CreateRole
• iam:DeleteRole
• iam:ListRolePolicies
• iam:AttachRolePolicy
• iam:DetachRolePolicy
• iam:GetInstanceProfile
• iam:CreateInstanceProfile
• iam:ListInstanceProfilesForRole
• iam:AddRoleToInstanceProfile
• iam:RemoveRoleFromInstanceProfile
• iam:DeleteInstanceProfile
• ec2:DescribeSecurityGroups
• ec2:CreateSecurityGroup
• ec2:DeleteSecurityGroup
• ec2:AuthorizeSecurityGroupIngress
• ec2:AuthorizeSecurityGroupEgress
• ec2:RevokeSecurityGroupEgress
• ec2:ImportKeyPair
• ec2:DescribeKeyPairs
• ec2:DeleteKeyPair
• ec2:CreateTags
• ec2:DescribeImages
• ec2:DescribeNetworkInterfaces
• ecs:DescribeClusters
• ecs:CreateCluster
• ecs:DeleteCluster
• autoscaling:DescribeLaunchConfigurations
• autoscaling:CreateLaunchConfiguration
• autoscaling:DeleteLaunchConfiguration
• autoscaling:DescribeScalingActivities
• autoscaling:DescribeAutoScalingGroups
• autoscaling:CreateAutoScalingGroup
• autoscaling:UpdateAutoScalingGroup
• autoscaling:DeleteAutoScalingGroup
• logs:CreateLogGroup
• logs:DescribeLogGroups
• logs:ListTagsLogGroup
• logs:DeleteLogGroup

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)
• 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

When a deployment identifier is provided via an environment variable, infrastructure will not be destroyed at the end of test execution. This can be useful during development to avoid lengthy provision and destroy cycles.

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-assumable-roles-policy. 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.