Terraform AWS Classic Load Balancer

A Terraform module for building a classic load balancer in AWS.

The 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
  • Deployed across the provided subnet IDs
  • Either internal or internet-facing as specified
  • With listeners for each of the supplied listener configurations
  • With a health check using the specified target
  • With connection draining as specified
• A security group allowing access to/from the load balancer according to the specified access control and egress CIDRs configuration
• A security group for use by instances allowing access from the load balancer according to the specified access control configuration
• A DNS entry
  • In the public hosted zone if specified
  • In the private hosted zone if specified

Usage

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

module "classic_load_balancer" {
  source  = "infrablocks/classic-load-balancer/aws"
  version = "0.1.7"

  region = "eu-west-2"
  vpc_id = "vpc-fb7dc365"
  subnet_ids = "subnet-ae4533c4,subnet-443e6b12"
  
  component = "important-component"
  deployment_identifier = "production"
  
  domain_name = "example.com"
  public_zone_id = "Z1WA3EVJBXSQ2V"
  private_zone_id = "Z3CVA9QD5NHSW3"
  
  listeners = [
    {
      lb_port = 443
      lb_protocol = "HTTPS"
      instance_port = 443
      instance_protocol = "HTTPS"
      ssl_certificate_id = "arn:aws:iam::123456789012:server-certificate/default"
    },
    {
      lb_port = 6567
      lb_protocol = "TCP"
      instance_port = 6567
      instance_protocol = "TCP"
    }
  ]
  
  access_control = [
    {
      lb_port = 443
      instance_port = 443
      allow_cidr = '0.0.0.0/0'
    },
    {
      lb_port = 6567
      instance_port = 6567
      allow_cidr = '10.0.0.0/8'
    }
  ]
  
  egress_cidrs = '10.0.0.0/8'
  
  health_check_target = 'HTTPS:443/ping'
  health_check_timeout = 10
  health_check_interval = 30
  health_check_unhealthy_threshold = 5
  health_check_healthy_threshold = 5

  enable_cross_zone_load_balancing = 'yes'

  enable_connection_draining = 'yes'
  connection_draining_timeout = 60

  idle_timeout = 60

  include_public_dns_record = 'yes'
  include_private_dns_record = 'yes'

  expose_to_public_internet = 'yes'
}

As mentioned above, the 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	-	yes
component	The component for which the load balancer is being created	-	yes
deployment_identifier	An identifier for this instantiation	-	yes
domain_name	The domain name of the supplied Route 53 zones	-	yes
public_zone_id	The ID of the public Route 53 zone	-	if include_public_dns_record is yes
private_zone_id	The ID of the private Route 53 zone	-	if include_private_dns_record is yes
listeners	A list of listener configurations for the ELB	-	yes
access_control	A list of access control configurations for the security groups	-	yes
egress_cidrs	The CIDRs that the load balancer is allowed to access	The CIDR of the VPC	no
health_check_target	The target to use for health checks	TCP:80	yes
health_check_timeout	The time after which a health check is considered failed in seconds	5	yes
health_check_interval	The time between health check attempts in seconds	30	yes
health_check_unhealthy_threshold	The number of failed health checks before an instance is taken out of service	2	yes
health_check_healthy_threshold	The number of successful health checks before an instance is put into service	10	yes
enable_cross_zone_load_balancing	Whether or not to enable cross zone load balancing ("yes" or "no")	yes	yes
enable_connection_draining	Whether or not to enable connection draining ("yes" or "no")	no	yes
connection_draining_timeout	The time after which connection draining is aborted in seconds	300	yes
idle_timeout	The time after which idle connections are closed	60	yes
include_public_dns_record	Whether or not to create a public DNS entry ("yes" or "no")	no	yes
include_private_dns_record	Whether or not to create a private DNS entry ("yes" or "no")	yes	yes
expose_to_public_internet	Whether or not to the ELB should be internet facing ("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 address of the DNS record(s) for the created ELB
security_group_id	The ID of the ELB security group
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 integration-test@example.com -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-application-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.