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Terraform AWS ECS Load Balancer

CircleCI

A Terraform module for building an elastic load balancer for an ECS service in AWS.

The ECS load balancer requires:

  • An existing VPC
  • Some existing subnets
  • A domain name and public and private hosted zones

The ECS load balancer consists of:

  • An ELB
    • Listening as HTTPS on port 443 using the provided certificate
    • Forwarding as HTTP on the provided service port to any registered instances
    • Using cross zone load balancing across the provided subnet IDs
    • Either internal or internet-facing depending on the provided parameter
    • With a health check using the specified target
  • A security group allowing access to the load balancer on port 443 from the specified CIDRs
  • A security group for use by targets allowing access from the load balancer on the service port.
  • A DNS entry for the service
    • In the public hosted zone if requested
    • In the private hosted zone if requested

Diagram of infrastructure managed by this module

Usage

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

module "ecs_load_balancer" {
  source = "infrablocks/ecs-load-balancer/aws"
  version = "0.1.10"

  region = "eu-west-2"
  vpc_id = "vpc-fb7dc365"
  subnet_ids = "subnet-ae4533c4,subnet-443e6b12"
  
  component = "important-component"
  deployment_identifier = "production"
  
  service_name = "memcache"
  service_port = "11211"
  service_certificate_arn = "arn:aws:acm:eu-west-2:121408295202:certificate/4e0452c7-d32d-4abd-b5f2-69490e83c936"
  
  domain_name = "example.com"
  public_zone_id = "Z1WA3EVJBXSQ2V"
  private_zone_id = "Z3CVA9QD5NHSW3"
  
  health_check_target = "TCP:11211"
  
  allow_cidrs = [
    "100.10.10.0/24",
    "200.20.0.0/16"
  ]
  
  include_public_dns_record = "yes"
  include_private_dns_record = "yes"
  
  expose_to_public_internet = "yes"
}

As mentioned above, the elastic load balancer 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

Name Description Default Required
region The region into which to deploy the load balancer - yes
vpc_id The ID of the VPC into which to deploy the load balancer - yes
subnet_ids The IDs of the subnets for the ELB to deploy into - yes
component The component for which the load balancer is being created - yes
deployment_identifier An identifier for this instantiation - yes
service_name The name of the service for which the ELB is being created default yes
service_port The port on which the service containers are listening - yes
service_certificate_arn The ARN of a certificate to use for TLS terminating at the ELB - yes
domain_name The domain name of the supplied Route 53 zones - yes
public_zone_id The ID of the public Route 53 zone - yes
private_zone_id The ID of the private Route 53 zone - yes
health_check_target The target to use for health checks HTTP:80/ping yes
allow_cidrs A list of CIDRs from which the ELB is reachable - yes
egress_cidrs A list of CIDRs which the ELB can reach the CIDR of the VPC no
include_public_dns_record Whether or not to create a public DNS record ("yes" or "no") "no" yes
include_private_dns_record Whether or not to create a private DNS record ("yes" or "no") "yes" yes
expose_to_public_internet Whether or not the ELB is publicly accessible ("yes" or "no") "no" yes

Outputs

Name Description
name The name of the created ELB
zone_id The zone ID of the created ELB
dns_name The DNS name of the created ELB
address The name of the service DNS record
security_group_id The ID of the security group associated with the ELB
open_to_load_balancer_security_group_id The ID of the security group allowing access from the ELB

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

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.

By default, providers will be downloaded for each terraform execution. To cache providers between calls:

TF_PLUGIN_CACHE_DIR="$HOME/.terraform.d/plugin-cache" 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 -sha256 -days 3650 -nodes \
  -keyout config/secrets/certificates/ssl.key \
  -out config/secrets/certificates/cert.pem \
  -subj /CN=example.com \
  -reqexts SAN \
  -config <(cat /etc/ssl/openssl.cnf \
    <(printf "\n[SAN]\nsubjectAltName=DNS:example.com,DNS:www.example.com,IP:10.0.0.1"))

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-load-balancer. 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.