Terraform AWS Application Load Balancer

A Terraform module for building an application load balancer in AWS.

The load balancer requires:

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

The application load balancer consists of:

• An ALB
  • Deployed across the provided subnet IDs
  • Either internal or internet-facing as specified
  • 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 "application_load_balancer" {
  source  = "infrablocks/application-load-balancer/aws"
  version = "4.0.0"

  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

  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 ALB.	-	Yes
component	The component for which the load balancer is being created.	-	Yes
deployment_identifier	An identifier for this instantiation.	-	Yes
idle_timeout	The time after which idle connections are closed.	60	No
expose_to_public_internet	Whether or not to the ALB should be internet facing ("yes" or "no").	"no"	No
security_groups	Details of security groups to add to the ALB, including the default security group.	{ default: { associate: "yes", ingress_rule: { include: "yes", cidrs: null }, egress_rule: { include: "yes", from_port: 0, to_port: 65535, cidrs: null } } }	No
dns	Details of DNS records to point at the created load balancer. Expects a domain_name, used to create each record and a list of records to create. Each record object includes a zone_id referencing the hosted zone in which to create the record.	{ domain_name: null, records: [] }	No
target_groups	Details of target groups to create.	[]	No
listeners	Details of listeners to create.	[]	No

Outputs

Name	Description
name	The name of the created ALB.
vpc_id	The VPC ID of the created ALB.
id	The ID of the created ALB.
arn	The ARN of the created ALB.
arn_suffix	The ARN suffix of the created ALB.
zone_id	The zone ID of the created ALB.
dns_name	The DNS name of the created ALB.
address	The address of the DNS record(s) for the created ALB.
target_groups	Details of the created target groups.
listeners	Details pf the created listeners.

Compatibility

This module is compatible with Terraform versions greater than or equal to Terraform 1.0 and Terraform AWS provider versions greater than or equal to 3.27.

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 run the full build, including unit and integration tests, execute:

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

To run the unit tests, execute:

aws-vault exec <profile> -- ./go test:unit

To run the integration tests, execute:

aws-vault exec <profile> -- ./go test:integration

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. For example, to run the unit tests with a seed of "testing", execute:

SEED=testing aws-vault exec <profile> -- ./go test:unit

When a seed 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.

To subsequently destroy unit test infrastructure for a given seed:

FORCE_DESTROY=yes SEED=testing aws-vault exec <profile> -- ./go test:unit

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-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.