Infracost Atlantis Integration

This repo shows how Infracost can be used with Atlantis, so you can see cloud cost estimates for Terraform in pull requests 💰

Follow our migration guide if you used our old version of this repo.

Usage methods

Since Atlantis does not have a plugins concept, you need to make two decisions to integrate it with Infracost:

1. Which deployment option do you want to use?

a) Use our Docker images (recommended)

Use our infracost-atlantis Docker images that extend the Atlantis image to add Infracost. We maintain tags for the latest two 0.x versions of Atlantis:

• infracost/infracost-atlantis:atlantis0.19-infracost0.10 latest patch version of Atlantis v0.19 and Infracost v0.10
• infracost/infracost-atlantis:atlantis0.18-infracost0.10 latest patch version of Atlantis v0.18 and Infracost v0.10
• infracost/infracost-atlantis:latest latest versions of Atlantis and Infracost

b) Build your own Docker image

If you already use a custom Docker image for Atlantis, copy the top RUN command from this Dockerfile into your Dockerfile.

c) Install in pre-workflow (good for testing)

Use Atlantis pre_workflow_hooks to dynamically install the Infracost CLI on a running Atlantis server (shown in the following repos.yml example). This enables you to test Infracost without changing your Docker image by installing it on each workflow run. Once you're happy with the results, you can use one of the above methods.

To use this method, add the following pre_workflow_hook to your chosen option in the next step. Also change references to the Infracost CLI invocation to /tmp/infracost in the the next step. Environment variables such as INFRACOST_API_KEY also need to be passed into the Atlantis container.

repos:
  - id: /.*/
    workflow: terraform-infracost
    pre_workflow_hooks:
      # Install Infracost, use `/tmp/infracost` to run the CLI in step 2
      - run: |
          /tmp/infracost --version && [ $(/tmp/infracost --version 2>&1 | grep -c "A new version of Infracost is available") = 0 ] || \
            curl -L https://infracost.io/downloads/v0.10/infracost-linux-amd64.tar.gz --output infracost.tar.gz && \
            tar -xvf infracost.tar.gz && \
            mv infracost-linux-amd64 /tmp/infracost

2. How do you want multiple Terraform directories/workspaces to be handled?

This option depends on what version of Atlantis you have and how you'd like to handle cost estimates for multiple Terraform directories/workspaces. The following table explains the options and links to instructions as well as screenshots.

	If you're using Atlantis 0.18.2 or newer	If you're using older than Atlantis 0.18.2
a) Recommended: combine cost estimates from multiple Terraform directories/workspaces into one Infracost pull request comment. Enables you to see the total cost estimate in one table.	Use this option	Not possible since post_workflow_hooks were added in Atlantis 0.18.2
b) Post one Infracost pull request comment per Terraform directory/workspace. This is the best option for users who cannot upgrade Atlantis yet.	Use this option
c) Append cost estimates to the bottom of Atlantis' "Show output" section of the pull request comment. Similar to option b) but the cost estimate is somewhat hidden. This is how our legacy integration worked but most users we talked to wanted option a).	Use this option

Additional examples

The following examples might be helpful to use alongside the above examples:

• Slack: post cost estimates to Slack
• Conftest: check cost policies using Atlantis' native Conftest integration and Infracost cost estimates.

If you do not use Conftest/Open Policy Agent, you can still set thresholds using bash and jq so notifications or pull request comments are only sent when cost thresholds are exceeded.

Atlantis usage notes

Private Terraform modules

To use with Terraform modules that are hosted in a private git repository you can add the --write-git-creds flag to your atlantis server command.

Terraform Cloud/Enterprise

To use with Terraform Cloud/Enterprise you can add the following flags to your atlantis server command: --tfe-hostname='MY_TFE_HOSTNAME' --tfe-token='MY_TFE_TOKEN'.

Terragrunt

If you use Atlantis with Terragrunt, you should:

1. Update your Docker image to include terragrunt, for example:

   FROM infracost/infracost-atlantis:latest
   
   RUN curl -L https://github.com/gruntwork-io/terragrunt/releases/download/v0.36.0/terragrunt_linux_amd64 --output terragrunt && \
       chmod +x terragrunt && \
       mv terragrunt /usr/local/bin

2. Add the following YAML spec to repos.yaml or atlantis.yaml config files, altering it to fit your terragrunt project:

   repos:
     - id: /.*/
       workflow: terragrunt-infracost
   workflows:
     terragrunt-infracost:
       plan:
         steps:
           - env:
               name: INFRACOST_OUTPUT
               command: 'echo "/tmp/$BASE_REPO_OWNER-$BASE_REPO_NAME-$PULL_NUM-$WORKSPACE-${REPO_REL_DIR//\//-}-infracost.json"'
           - env:
               name: TERRAGRUNT_TFPATH
               command: 'echo "terraform${ATLANTIS_TERRAFORM_VERSION}"'
           - run: terragrunt plan -out=$PLANFILE
           - run: terragrunt show -json $PLANFILE > $SHOWFILE
           # Add custom steps here from the examples mentioned elsewhere in this readme

Overriding metadata

If you use Infracost Cloud, you might find it useful to override metadata such as the pull request author or title that is shown on the Infracost Cloud dashboard.

Contributing

Issues and pull requests are welcome! For development details, see the contributing guide. For major changes, including interface changes, please open an issue first to discuss what you would like to change. Join our community Slack channel, we are a friendly bunch and happy to help you get started :)

License

Apache License 2.0