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Infracost Atlantis Integration

This repo shows how Infracost can be used with Atlantis. It automatically adds a comment to the bottom of Atlantis' output showing the cost estimate difference if a percentage threshold is crossed. See this pull-request for a demo, expand the Show Output sections and scroll down to see the Infracost output.

This integration uses the latest version of Infracost by default as we regularly add support for more cloud resources. If you run into any issues, please join our community Slack channel; we'd be happy to guide you through it.

As mentioned in the FAQ, no cloud credentials, secrets, tags or resource identifiers are sent to the Cloud Pricing API. That API does not become aware of your cloud spend; it simply returns cloud prices to the CLI so calculations can be done on your machine. Infracost does not make any changes to your Terraform state or cloud resources.

Example screenshot

Usage methods

There are two methods of integrating Infracost with Atlantis:

  1. Use a custom Docker image that extends Atlantis' latest image to add Infracost. This is the recommended method.

  2. Send the $PLANFILE from Atlantis to the Infracost API with curl. Whilst this API deletes files from the server after they are processed, it is a good security practice to remove secrets from the file before sending it to the API. For example, AWS provides a grep command that can be used to do this.

1. Docker image

This method runs infracost diff using the $PLANFILE that Atlantis generates. The following steps describe how you can use this method:

  1. This Docker image extends the Atlantis image by adding the Infracost CLI and the infracost_atlantis_diff.sh script. If you already use a custom Docker image for Atlantis, copy the RUN commands from this Dockerfile into your Dockerfile.

  2. Update your Atlantis configuration to add a custom command that runs Infracost with the required environment variables, such as INFRACOST_API_KEY. The available environment variables are describe in the next section. The following example shows how this can be done, a similar thing can be done with the Atlantis yaml configs in either the Server Config file or Server Side Repo Config files.

    docker run infracost/infracost-atlantis:latest server \
  --gh-user=MY_GITHUB_USERNAME \
  --gh-token=MY_GITHUB_TOKEN \
  --gh-webhook-secret=MY_GITHUB_WEBHOOK_SECRET \
  --repo-allowlist='github.com/myorg/*' \
  --repo-config-json='
    {
      "repos": [
        {
          "id": "/.*/",
          "workflow": "terraform-infracost"
        }
      ],
      "workflows": {
        "terraform-infracost": {
          "plan": {
            "steps": [
              "init",
              "plan",
              {
                "env": {
                  "name": "INFRACOST_API_KEY",
                  "value": "MY_API_KEY"
                }
              },
              {
                "run": "/infracost_atlantis_diff.sh"
              }
            ]
          }
        }
      }
    }
  '

  3. Send a new pull request to change something in Terraform that costs money; a comment should be posted on the pull request by Atlantis, expand the Show Output section, at the bottom of which you should see the Infracost output. Set the atlantis_debug=true environment variable and see this page if there are issues.

Environment variables

This section describes the required environment variables. Other supported environment variables are described in the this page.

Terragrunt users should also read this page. Terraform Cloud/Enterprise users should also read this page.

INFRACOST_API_KEY

Required To get an API key download Infracost and run infracost register.

INFRACOST_TERRAFORM_BINARY

Optional Used to change the path to the terraform binary or version, should be set to the path of the Terraform or Terragrunt binary being used in Atlantis.

usage_file

Optional Path to Infracost usage file that specifies values for usage-based resources, see this example file for the available options.

percentage_threshold

Optional The absolute percentage threshold that triggers a pull request comment with the diff. Defaults to 0, meaning that a comment is posted if the cost estimate changes. For example, set to 5 to post a comment if the cost estimate changes by more than plus or minus 5%.

atlantis_debug

Optional Enable debug mode in infracost_atlantis_diff.sh so it shows the steps being run in the Atlantis pull request comment (default is false).

2. Infracost API

  1. Update your Atlantis configuration to add a custom command that runs Infracost as shown in the following example. You should only need to update MY_API_KEY to your Infracost API key. A similar thing can be done with the Atlantis yaml configs in either the Server Config file or Server Side Repo Config files. Optionally add a step to remove secrets from the plan JSON file before sending it to the API.
docker run infracost/infracost-atlantis:latest server \
  --gh-user=MY_GITHUB_USERNAME \
  --gh-token=MY_GITHUB_TOKEN \
  --gh-webhook-secret=MY_GITHUB_WEBHOOK_SECRET \
  --repo-allowlist='github.com/myorg/*' \
  --repo-config-json='
    {
      "repos": [
        {
          "id": "/.*/",
          "workflow": "terraform-infracost"
        }
      ],
      "workflows": {
        "terraform-infracost": {
          "plan": {
            "steps": [
              "init",
              "plan",
              {
                "run": "terraform show -json $PLANFILE > $PLANFILE.json"
              },
              {
                "run": "echo \"#####\" && echo && echo Infracost output:"
              },
              {
                "run": "curl -s -X POST -H \"x-api-key: MY_API_KEY\" -F \"ci-platform=atlantis\" -F \"terraform-json-file=@$PLANFILE.json\" -F \"no-color=true\" https://pricing.api.infracost.io/terraform-json-file"
              },
              {
                "run": "rm -rf $PLANFILE.json"
              }
            ]
          }
        }
      }
    }
  '
  1. Send a new pull request to change something in Terraform that costs money; a comment should be posted on the pull request by Atlantis, expand the Show Output section, at the bottom of which you should see the Infracost output. The output should include errors if there are issues.

Contributing

Merge requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

License

Apache License 2.0