mzupan / terraform-plan

GitHub action to generate a terraform plan

terraform-plan action

This is one of a suite of terraform related actions - find them at dflook/terraform-github-actions.

This actions generates a terraform plan. If the triggering event relates to a PR it will add a comment on the PR containing the generated plan.

The GITHUB_TOKEN environment variable must be set for the PR comment to be added. The action can be run on other events, which prints the plan to the workflow log.

The dflook/terraform-apply action can be used to apply the generated plan.

Inputs

• path

  Path to the terraform root module to apply

  • Type: string
  • Optional
  • Default: The action workspace

• workspace

  Terraform workspace to run the plan for

  • Type: string
  • Optional
  • Default: default

• label

  A friendly name for the environment the terraform configuration is for. This will be used in the PR comment for easy identification.

  If set, must be the same as the label used in the corresponding terraform-apply command.

  • Type: string
  • Optional

• variables

  Variables to set for the terraform plan. This should be valid terraform syntax - like a variable definition file.

  with:
    variables: |
      image_id = "${{ secrets.AMI_ID }}"
      availability_zone_names = [
        "us-east-1a",
        "us-west-1c",
      ]

  Variables set here override any given in var_files. This can be used with remote backends such as Terraform Cloud/Enterprise, with variables set in the remote workspace having precedence.

  ⚠️ Secret values are not masked in the PR comment. Set a label to avoid revealing the variables in the PR.

  • Type: string
  • Optional

• var_file

  List of tfvars files to use, one per line. Paths should be relative to the GitHub Actions workspace

  with:
    var_file: |
      common.tfvars
      prod.tfvars

  This can be used with remote backends such as Terraform Cloud/Enterprise, with variables set in the remote workspace having precedence.

  • Type: string
  • Optional

• backend_config

  List of terraform backend config values, one per line.

  with:
    backend_config: token=${{ secrets.BACKEND_TOKEN }}

  • Type: string
  • Optional

• backend_config_file

  List of terraform backend config files to use, one per line. Paths should be relative to the GitHub Actions workspace

  with:
    backend_config_file: prod.backend.tfvars

  • Type: string
  • Optional

• replace

  List of resources to replace, one per line.

  Only available with terraform versions that support replace (v0.15.2 onwards).

  with:
    replace: |
      random_password.database

  • Type: string
  • Optional

• target

  List of resources to apply, one per line. The plan will be limited to these resources and their dependencies.

  with:
    target: |
      kubernetes_secret.tls_cert_public
      kubernetes_secret.tls_cert_private

  • Type: string
  • Optional

• add_github_comment

  The default is true, which adds a comment to the PR with the results of the plan. Set to changes-only to add a comment only when the plan indicates there are changes to apply. Set to false to disable the comment - the plan will still appear in the workflow log.

  • Type: string
  • Optional
  • Default: true

• parallelism

  Limit the number of concurrent operations

  • Type: number
  • Optional
  • Default: The terraform default (10)

• var

  ⚠️ Deprecated: Use the variables input instead.

  Comma separated list of terraform vars to set.

  This is deprecated due to the following limitations:

  • Only primitive types can be set with var - number, bool and string.
  • String values may not contain a comma.
  • Values set with var will be overridden by values contained in var_files
  • Does not work with the remote backend

  You can change from var to variables by putting each variable on a separate line and ensuring each string value is quoted.

  For example:

  with:
    var: instance_type=m5.xlarge,nat_type=instance

  Becomes:

  with:
    variables: |
      instance_type="m5.xlarge"
      nat_type="instance"

  • Type: string
  • Optional

Environment Variables

• GITHUB_TOKEN

  The GitHub authorization token to use to create comments on a PR. The token provided by GitHub Actions can be used - it can be passed by using the ${{ secrets.GITHUB_TOKEN }} expression, e.g.

  env:
    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

  The token provided by GitHub Actions will work with the default permissions. The minimum permissions are pull-requests: write. It will also likely need contents: read so the job can checkout the repo.

  You can also use a Personal Access Token which has the repo scope. The GitHub user that owns the PAT will be the PR comment author.

  • Type: string
  • Optional

• TERRAFORM_CLOUD_TOKENS

  API tokens for terraform cloud hosts, of the form <host>=<token>. Multiple tokens may be specified, one per line. These tokens may be used with the remote backend and for fetching required modules from the registry.

  e.g for terraform cloud:

  env:
    TERRAFORM_CLOUD_TOKENS: app.terraform.io=${{ secrets.TF_CLOUD_TOKEN }}

  With Terraform Enterprise or other registries:

  env:
    TERRAFORM_CLOUD_TOKENS: |
      app.terraform.io=${{ secrets.TF_CLOUD_TOKEN }}
      terraform.example.com=${{ secrets.TF_REGISTRY_TOKEN }}

  • Type: string
  • Optional

• TERRAFORM_SSH_KEY

  A SSH private key that terraform will use to fetch git/mercurial module sources.

  This should be in PEM format.

  For example:

  env:
    TERRAFORM_SSH_KEY: ${{ secrets.TERRAFORM_SSH_KEY }}

  • Type: string
  • Optional

• TERRAFORM_HTTP_CREDENTIALS

  Credentials that will be used for fetching modules sources with git::http://, git::https://, http:// & https:// schemes.

  Credentials have the format <host>=<username>:<password>. Multiple credentials may be specified, one per line.

  Each credential is evaluated in order, and the first matching credentials are used.

  Credentials that are used by git (git::http://, git::https://) allow a path after the hostname. Paths are ignored by http:// & https:// schemes. For git module sources, a credential matches if each mentioned path segment is an exact match.

  For example:

  env:
    TERRAFORM_HTTP_CREDENTIALS: |
      example.com=dflook:${{ secrets.HTTPS_PASSWORD }}
      github.com/dflook/terraform-github-actions.git=dflook-actions:${{ secrets.ACTIONS_PAT }}
      github.com/dflook=dflook:${{ secrets.DFLOOK_PAT }}
      github.com=graham:${{ secrets.GITHUB_PAT }}  

  • Type: string
  • Optional

• TF_PLAN_COLLAPSE_LENGTH

  When PR comments are enabled, the terraform output is included in a collapsable pane.

  If a terraform plan has fewer lines than this value, the pane is expanded by default when the comment is displayed.

  env:
    TF_PLAN_COLLAPSE_LENGTH: 30

  • Type: integer
  • Optional
  • Default: 10

• TERRAFORM_PRE_RUN

  A set of commands that will be ran prior to terraform init. This can be used to customise the environment before running terraform.

  The runtime environment for these actions is subject to change in minor version releases. If using this environment variable, specify the minor version of the action to use.

  The runtime image is currently based on debian:bullseye, with the command run using bash -xeo pipefail.

  For example:

  env:
    TERRAFORM_PRE_RUN: |
      # Install latest Azure CLI
      curl -skL https://aka.ms/InstallAzureCLIDeb | bash
      
      # Install postgres client
      apt-get install -y --no-install-recommends postgresql-client

  • Type: string
  • Optional

Outputs

• changes

  Set to 'true' if the plan would apply any changes, 'false' if it wouldn't.

  Note that with terraform <0.13 an apply may still be needed to update any outputs, even if no resources would change. With terraform >=0.13 this is correctly set to 'true' whenever an apply needs to be run.

  • Type: boolean

• json_plan_path

  This is the path to the generated plan in JSON Output Format The path is relative to the Actions workspace.

  This is not available when using terraform 0.11 or earlier.

  • Type: string

• text_plan_path

  This is the path to the generated plan in a human-readable format. The path is relative to the Actions workspace.

  • Type: string

• to_add

  The number of resources that would be added by this plan.

  • Type: number

• to_change

  The number of resources that would be changed by this plan.

  • Type: number

• to_destroy

  The number of resources that would be destroyed by this plan.

  • Type: number

• run_id

  If the root module uses the remote or cloud backend in remote execution mode, this output will be set to the remote run id.

  • Type: string

Example usage

Automatically generating a plan

This example workflow runs on every push to an open pull request, and create or updates a comment with the terraform plan

name: PR Plan

on: [pull_request]

jobs:
  plan:
    runs-on: ubuntu-latest
    name: Create terraform plan
    env:
      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}            
    steps:
      - name: Checkout
        uses: actions/checkout@v2

      - name: terraform plan
        uses: dflook/terraform-plan@v1
        with:
          path: my-terraform-config

A full example of inputs

This example workflow demonstrates most of the available inputs:

• The environment variables are set at the workflow level.
• The PR comment will be labelled production, and the plan will use the prod workspace.
• Variables are read from env/prod.tfvars, with turbo_mode overridden to true.
• The backend config is taken from env/prod.backend, and the token is set from a secret.

name: PR Plan

on: [pull_request]

env:
  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
  TERRAFORM_CLOUD_TOKENS: terraform.example.com=${{ secrets.TF_REGISTRY_TOKEN }}
  TERRAFORM_SSH_KEY: ${{ secrets.TERRAFORM_SSH_KEY }}

jobs:
  plan:
    runs-on: ubuntu-latest
    name: Create terraform plan
    steps:
      - name: Checkout
        uses: actions/checkout@v2

      - name: terraform plan
        uses: dflook/terraform-plan@v1
        with:
          path: my-terraform-config
          label: production
          workspace: prod
          var_file: env/prod.tfvars
          variables: |
            turbo_mode=true
          backend_config_file: env/prod.backend
          backend_config: token=${{ secrets.BACKEND_TOKEN }}

Generating a plan using a comment

This workflow generates a plan on demand, triggered by someone commenting terraform plan on the PR. The action will create or update a comment on the PR with the generated plan.

name: Terraform Plan

on: [issue_comment]

jobs:
  plan:
    if: ${{ github.event.issue.pull_request && contains(github.event.comment.body, 'terraform plan') }}
    runs-on: ubuntu-latest
    name: Create terraform plan
    env:
      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
    steps:
      - name: Checkout
        uses: actions/checkout@v2
        with:
          ref: refs/pull/${{ github.event.issue.number }}/merge

      - name: terraform plan
        uses: dflook/terraform-plan@v1
        with:
          path: my-terraform-config