terragrunt-atlantis-config for Mac

Terragrunt Atlantis Config

Generate Atlantis Config for Terragrunt projects.

What is this?

Atlantis is an awesome tool for Terraform pull request automation. Each repo can have a YAML config file that defines Terraform module dependencies, so that PRs that affect dependent modules will automatically generate terraform plans for those modules.

Terragrunt is a Terraform wrapper, which has the concept of dependencies built into its configuration.

This tool creates Atlantis YAML configurations for Terragrunt projects by: Finding all terragrunt.hcl in a repo Evaluating their dependency, terraform, locals, and other source blocks to find their dependencies Creating a Directed Acyclic Graph of all dependencies Constructing and logging YAML in Atlantis' config spec that reflects the graph

This is especially useful for organizations that use monorepos for their Terragrunt config (as we do at Transcend), and have thousands of lines of config.

Integrate into your Atlantis Server

The recommended way to use this tool is to install it onto your Atlantis server, and then use a Pre-Workflow hook to run it after every clone. This way, Atlantis can automatically determine what modules should be planned/applied for any change to your repository.

To get started, add a pre_workflow_hooks field to your repos section of your server-side repo config:

Then, make sure terragrunt-atlantis-config is present on your Atlantis server. There are many different ways to configure a server, but this example in Packer should show the bash commands you'll need just about anywhere:

and just like that, your developers should never have to worry about an atlantis.yaml file, or even need to know what it is.

Extra dependencies

For basic cases, this tool can sniff out all dependencies in a module. However, you may have times when you want to add in additional dependencies such as: You use Terragrunt's read_terragrunt_config function in your locals, and want to depend on the read file Your Terragrunt module should be run anytime some non-terragrunt file is updated, such as a Dockerfile or Packer template You want to run _all_ modules any time your product has a major version bump You believe a module should be reapplied any time some other file or directory is updated

In these cases, you can customize the locals block in that Terragrunt module to have a field named extra_atlantis_dependencies with a list of values you want included in the config, such as:

In your atlantis.yaml file, you will end up seeing output like: