🚀 Infracost GitHub Action

               

This GitHub Action downloads a Terraform plan artifact and runs Infracost to generate a cost estimate. It supports workflows where the Terraform plan is created in a separate job or workflow, and reused across CI/CD stages.

It also supports dynamic cost thresholding (max_cost) using a GitHub Gist that maps environments and repositories to their cost budgets.

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🧾 Inputs

Name	Description
terraform-dir	Relative path to the Terraform directory (e.g., tf, infrastructure).
release-tag	Git release tag to check out. If omitted, the latest commit is used.
ci-pipeline	If true, includes the commit SHA in the Terraform state key.
s3-bucket	Name of the S3 bucket used for the Terraform state backend.
s3-region	AWS region where the S3 backend bucket is located (e.g., us-east-1).
tf-plan-name	Name of the Terraform plan artifact.
tf-plan-file	Base filename (without extension) for the Terraform plan output.
tf-vars-file	Optional Terraform variable file.
infracost-api-key	Infracost API key.
gist-id	Gist ID containing the Infracost configuration (e.g., repository/env → max cost).
gist-filename	Gist filename (default: infracost-config.json).
environment	GitHub environment name (e.g., dev, test, prod) used to look up max cost.
max-cost	Optional fallback cost threshold. Used if not found in Gist (e.g., 100.00).

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📤 Outputs

Name	Description
monthly-cost	Total monthly cost calculated by Infracost.
max-cost	Resolved maximum cost threshold from Gist or fallback value.

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💡 Example Usage

name: Infracost Breakdown

on:
  workflow_dispatch:

jobs:
  infracost:
    runs-on: ubuntu-latest
    permissions:
      id-token: write
      contents: read
    steps:
      - name: Run Infracost Analysis
        uses: subhamay-bhattacharyya-gha/infracost-action@main
        with:
          terraform-dir: tf
          release-tag: ""
          ci-pipeline: "true"
          s3-bucket: my-terraform-state-bucket
          s3-region: us-east-1
          tf-plan-name: terraform-plan
          tf-plan-file: tfplan
          tf-vars-file: terraform.tfvars
          infracost-api-key: ${{ secrets.INFRACOST_API_KEY }}
          gist-id: ${{ secrets.infracost-gist-id }}
          gist-filename: ${{ secrets.gist-filename }}
          environment: devl

🧠 Gist JSON Format Example

{
  "0002-terraform-template": {
    "ci": { "max_cost": 1.99 },
    "devl": { "max_cost": 1.00 },
    "test": { "max_cost": 20.00 },
    "prod": { "max_cost": 80.00 }
  },
  "data-lake": {
    "devl": { "max_cost": 4.00 },
    "test": { "max_cost": 10.00 },
    "prod": { "max_cost": 100.00 }
  }
}

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🪪 License

MIT