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 configuration 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

Terraform versions

Terraform 0.12. Pin module version to ~> 1.0. Submit pull-requests to master branch.

Terraform 0.11. Pin module version to ~> 0.6.0. Submit pull-requests to terraform011 branch.

Usage

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

module "ecs_cluster" {
  source = "infrablocks/ecs-cluster/aws"
  version = "0.2.5"
  
  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 = "t2.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.

Inputs

Name	Description	Default	Required
region	The region into which to deploy the cluster	-	yes
vpc_id	The ID of the VPC into which to deploy the cluster	-	yes
subnet_ids	The IDs of the subnets for container instances	-	yes
component	The component this cluster will contain	-	yes
deployment_identifier	An identifier for this instantiation	-	yes
cluster_name	The name of the cluster to create	default	yes
cluster_instance_ssh_public_key_path	The path to the public key to use for the container instances	-	yes
cluster_instance_type	The instance type of the container instances	t2.medium	yes
cluster_instance_root_block_device_size	The size in GB of the root block device on cluster instances	30	yes
cluster_instance_root_block_device_type	The type of the root block device on cluster instances ('standard', 'gp2', or 'io1')	standard	yes
cluster_instance_user_data_template	The contents of a template for container instance user data	see user-data	no
cluster_instance_amis	A map of regions to AMIs for the container instances	ECS optimised AMIs	yes
cluster_instance_iam_policy_contents	The contents of the cluster instance IAM policy	see policies	no
cluster_service_iam_policy_contents	The contents of the cluster service IAM policy	see policies	no
cluster_minimum_size	The minimum size of the ECS cluster	1	yes
cluster_maximum_size	The maximum size of the ECS cluster	10	yes
cluster_desired_capacity	The desired capacity of the ECS cluster	3	yes
associate_public_ip_addresses	Whether or not to associate public IP addresses with ECS container instances ("yes" or "no")	"no"	yes
include_default_ingress_rule	Whether or not to include the default ingress rule on the ECS container instances security group ("yes" or "no")	"yes"	yes
include_default_egress_rule	Whether or not to include the default egress rule on the ECS container instances security group ("yes" or "no")	"yes"	yes
allowed_cidrs	The CIDRs allowed access to containers	["10.0.0.0/8"]	if include_default_ingress_rule is "yes"
egress_cidrs	The CIDRs accessible from containers	["0.0.0.0/0"]	if include_default_egress_rule is "yes"
launch_configuration_create_before_destroy	Whether or not to destroy the launch configuration before creating a new one ("yes" or "no")	"yes"	no
security_groups	The list of security group IDs to associate with the cluster in addition to the default security group	[]	no

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 with be passed the cluster name as cluster_name. If none is supplied, a default will be used.

Outputs

Name	Description
cluster_id	The ID of the created ECS cluster
cluster_name	The name of the created ECS cluster
cluster_arn	The ARN of the created ECS cluster
autoscaling_group_name	The name of the autoscaling group for the ECS container instances
launch_configuration_name	The name of the launch configuration for the ECS container instances
security_group_id	The ID of the default security group associated with the ECS container instances
instance_role_arn	The ARN of the container instance role
instance_role_id	The ID of the container instance role
instance_policy_arn	The ARN of the container instance policy
instance_policy_id	The ID of the container instance policy
service_role_arn	The ARN of the ECS service role
service_role_id	The ID of the ECS service role
service_policy_arn	The ARN of the ECS service policy
service_policy_id	The ID of the ECS service policy
log_group	The name of the default log group for the cluster

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 (2.3.1)
• Bundler
• git
• git-crypt
• gnupg
• direnv

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 2.3.1
rbenv rehash
rbenv local 2.3.1
gem install bundler

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

# 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

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

./go

To provision the module prerequisites:

./go deployment:prerequisites:provision[<deployment_identifier>]

To provision the module contents:

./go deployment:harness:provision[<deployment_identifier>]

To destroy the module contents:

./go deployment:harness:destroy[<deployment_identifier>]

To destroy the module prerequisites:

./go deployment:prerequisites:destroy[<deployment_identifier>]

Common Tasks

Generating an SSH key pair

To generate an SSH key pair:

ssh-keygen -t rsa -b 4096 -C integration-test@example.com -N '' -f config/secrets/keys/bastion/ssh

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/tobyclemson/terraform-aws-ecs-cluster. 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.