This repo, along with the terragrunt-infrastructure-modules-example repo, show an example file/folder structure you can use with Terragrunt to keep your Terraform and OpenTofu code DRY. For background information, check out the Keep your code DRY section of the Terragrunt documentation.
This repo shows an example of how to use the modules from the terragrunt-infrastructure-modules-example repo to
deploy an Auto Scaling Group (ASG) and a MySQL DB across three environments (qa, stage, prod) and two AWS accounts
(non-prod, prod), all with minimal duplication of code. That's because there is just a single copy of
the code, defined in the terragrunt-infrastructure-modules-example repo, and in this repo, we solely define
terragrunt.hcl files that reference that code (at a specific version, too!) and fill in variables specific to each
environment.
Be sure to read through the Terragrunt documentation on DRY Architectures to understand the features of Terragrunt used in this folder organization.
Note: This code is solely for demonstration purposes. This is not production-ready code, so use at your own risk. If you are interested in battle-tested, production-ready Terraform code, check out Gruntwork.
- Install OpenTofu version
1.6.0or newer and Terragrunt versionv0.52.0or newer. - Update the
bucketparameter in the rootterragrunt.hcl. We use S3 as a Terraform backend to store your state, and S3 bucket names must be globally unique. The name currently in the file is already taken, so you'll have to specify your own. Alternatives, you can set the environment variableTG_BUCKET_PREFIXto set a custom prefix. - Update the
account_nameandaws_account_idparameters innon-prod/account.hclandprod/account.hclwith the names and IDs of accounts you want to use for non production and production workloads, respectively. - Configure your AWS credentials using one of the supported authentication mechanisms.
cdinto the module's folder (e.g.cd non-prod/us-east-1/qa/mysql).- Note: if you're deploying the MySQL DB, you'll need to configure your DB password as an environment variable:
export TF_VAR_master_password=(...). - Run
terragrunt planto see the changes you're about to apply. - If the plan looks good, run
terragrunt apply.
cdinto the region folder (e.g.cd non-prod/us-east-1).- Configure the password for the MySQL DB as an environment variable:
export TF_VAR_master_password=(...). - Run
terragrunt run-all planto see all the changes you're about to apply. - If the plan looks good, run
terragrunt run-all apply.
After each module is finished deploying, it will write a bunch of outputs to the screen. For example, the ASG will output something like the following:
Outputs:
asg_name = tf-asg-00343cdb2415e9d5f20cda6620
asg_security_group_id = sg-d27df1a3
elb_dns_name = webserver-example-prod-1234567890.us-east-1.elb.amazonaws.com
elb_security_group_id = sg-fe62ee8f
url = http://webserver-example-prod-1234567890.us-east-1.elb.amazonaws.com:80
A minute or two after the deployment finishes, and the servers in the ASG have passed their health checks, you should
be able to test the url output in your browser or with curl:
curl http://webserver-example-prod-1234567890.us-east-1.elb.amazonaws.com:80
Hello, World
Similarly, the MySQL module produces outputs that will look something like this:
Outputs:
arn = arn:aws:rds:us-east-1:1234567890:db:tofu-00d7a11c1e02cf617f80bbe301
db_name = mysql_prod
endpoint = tofu-1234567890.abcdefghijklmonp.us-east-1.rds.amazonaws.com:3306
You can use the endpoint and db_name outputs with any MySQL client:
mysql --host=tofu-1234567890.abcdefghijklmonp.us-east-1.rds.amazonaws.com:3306 --user=admin --password mysql_prod
The code in this repo uses the following folder hierarchy:
account
└ _global
└ region
└ _global
└ environment
└ resource
Where:
-
Account: At the top level are each of your AWS accounts, such as
stage-account,prod-account,mgmt-account, etc. If you have everything deployed in a single AWS account, there will just be a single folder at the root (e.g.main-account). -
Region: Within each account, there will be one or more AWS regions, such as
us-east-1,eu-west-1, andap-southeast-2, where you've deployed resources. There may also be a_globalfolder that defines resources that are available across all the AWS regions in this account, such as IAM users, Route 53 hosted zones, and CloudTrail. -
Environment: Within each region, there will be one or more "environments", such as
qa,stage, etc. Typically, an environment will correspond to a single AWS Virtual Private Cloud (VPC), which isolates that environment from everything else in that AWS account. There may also be a_globalfolder that defines resources that are available across all the environments in this AWS region, such as Route 53 A records, SNS topics, and ECR repos. -
Resource: Within each environment, you deploy all the resources for that environment, such as EC2 Instances, Auto Scaling Groups, ECS Clusters, Databases, Load Balancers, and so on. Note that the code for most of these resources lives in the terragrunt-infrastructure-modules-example repo.
In the situation where you have multiple AWS accounts or regions, you often have to pass common variables down to each
of your modules. Rather than copy/pasting the same variables into each terragrunt.hcl file, in every region, and in
every environment, you can inherit them from the inputs defined in the root terragrunt.hcl file.
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