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tflint plugin

Installation

This plugin depends on tflint. If you use tflint version 0.29 or newer, you can leverage the tflint --init command to automatically install the plugin. Otherwise, you will need to download the tflint-ruleset-aws-serverless binary corresponding to your system from the releases page.

You can enable the Serverless Rules plugin by adding a plugin section in the .tflint.hcl file in your project:

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plugin "aws-serverless" {
  enabled = true
  version = "0.3.2"
  source = "github.com/awslabs/serverless-rules"
}

Usage

You can now run the tflint command, which will automatically use the Serverless Rules plugin:

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tflint

You can also try with a Terraform example provided in this repository. From the root folder of the repository, you can run:

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cd examples/tflint/
tflint

Sample outputs

If the Terraform configuration files fulfill the requirements for all the rules, tflint will return an empty output. Otherwise, tflint will output recommendations.

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$ tflint
$

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$ tflint
1 issue(s) found:

Warning: "tracing_config" is not present. (aws_lambda_function_tracing_rule)

    on main.tf line 20:

$

Ignoring rules

Serverless Rules is a set of recommended practices.

We recommend you to keep Error-level rules enabled. Non-error rules, for example Lambda Tracing, contain detailed scenarios on when it’s safe to ignore them.

When needed, you can ignore any specific rule that doesn’t match your environment.

Rules in tflint can be disabled either through the --disable-rule command-line argument or with the .tflint.hcl configuration file in the current working directory. See the tflint user guide for more information.

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# Disable the aws_lambda_function_tracing_rule rule
tflint --disable-rule aws_lambda_function_tracing_rule

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plugin "aws-serverless" {
  enabled = true
  version = "0.3.2"
  source = "github.com/awslabs/serverless-rules"
}

# Disable the aws_lambda_function_tracing_rule rule
rule "aws_lambda_function_tracing_rule" {
  enabled = false
}

Continuous integration

You can use Serverless Rules and tflint with your continuous integration tool to automatically check CloudFormation templates with rules from this project. For example, you can validate on pull requests, merge to your main branch, or before deploying to production.

If there are any issues with your template, tflint will return a non-zero error code.

AWS CodeBuild

Assuming that you are storing your terraform configuration files and a .tflint.hcl file at the root of your repository, you can create a buildspec file such as this one.

Important

Make sure that you include the aws-serverless plugin into your .tflint.hcl configuration file, otherwise tflint will not install this ruleset. See Installation for more information.

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env:
  variables:
    # TODO: replace "v0.29.0" with the latest version of tflint
    TFLINT_VERSION: "0.29.0"
    TFLINT_OS: "amd64"

phases:
  install:
    commands:
      # Install tflint
      - wget https://github.com/terraform-linters/tflint/releases/download/v${TFLINT_VERSION}/tflint_linux_${TFLINT_OS}.zip -O tflint.zip
      - unzip tflint.zip
      # Install tflint plugins
      - ./tflint --init
  pre_build:
    commands:
      - ./tflint

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env:
  variables:
    # TODO: replace "v0.29.0" with the latest version of tflint
    TFLINT_VERSION: "0.29.0"
    TFLINT_OS: "amd64"

phases:
  install:
    commands:
      # Install tflint
      - wget https://github.com/terraform-linters/tflint/releases/download/v${TFLINT_VERSION}/tflint_linux_${TFLINT_OS}.zip -O tflint.zip
      - unzip tflint.zip
      # Install tflint plugins
      - ./tflint --init
  pre_build:
    commands:
      - ./tflint -f junit > tflint_report.xml

reports:
  tflint:
    files:
      - tflint_report.xml

GitHub Actions

Assuming that you are storing your terraform configuration files and a .tflint.hcl file at the root of your repository, and that you are using main as your target branch for pull requests, you can create a GitHub actions workflow file such as this one:

Important

Make sure that you include the aws-serverless plugin into your .tflint.hcl configuration file, otherwise tflint will not install this ruleset. See Installation for more information.

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name: tflint-serverless

on:
  pull_request:
    branches:
      # TODO: replace this if you are not using 'main' as your target
      # branch for pull requests.
      - main

jobs:
  tflint-serverless:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Setup TFLint
        uses: terraform-linters/setup-tflint@v1
        with:
          tflint_version: v0.29.0
      - name: Install Terraform plugins
        run: tflint --init
      - name: Lint Terraform files
        run: tflint

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name: tflint-serverless

on:
  pull_request:
    branches:
      # TODO: replace this if you are not using 'main' as your target
      # branch for pull requests.
      - main

jobs:
  tflint-serverless:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Setup TFLint
        uses: terraform-linters/setup-tflint@v1
        with:
          tflint_version: v0.29.0
      - name: Install Terraform plugins
        run: tflint --init
      - name: Lint Terraform files
        run: tflint -f junit > tflint_report.xml
      - name: Publish test report
        uses: mikepenz/action-junit-report@v2
        # Only run this step on failure
        if: ${{ failure() }}
        with:
          report_paths: cfn_lint_report.xml

GitLab

Assuming that you are storing your terraform configuration files and a .tflint.hcl file at the root of your repository, you can create a .gitlab-ci.yml file such as this one:

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tflint-serverless:
  variables:
    # TODO: replace "v0.29.0" with the latest version of tflint
    TFLINT_VERSION: "0.29.0"
    TFLINT_OS: "amd64"
  only:
    - merge_requests
  script:
    # Install tflint
    - wget https://github.com/terraform-linters/tflint/releases/download/v${TFLINT_VERSION}/tflint_linux_${TFLINT_OS}.zip -O tflint.zip
    - unzip tflint.zip
    # Install tflint plugins
    - ./tflint --init
    # Run tflint
    - ./tflint

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tflint-serverless:
  variables:
    # TODO: replace "v0.29.0" with the latest version of tflint
    TFLINT_VERSION: "0.29.0"
    TFLINT_OS: "amd64"
  only:
    - merge_requests
  script:
    # Install tflint
    - wget https://github.com/terraform-linters/tflint/releases/download/v${TFLINT_VERSION}/tflint_linux_${TFLINT_OS}.zip -O tflint.zip
    - unzip tflint.zip
    # Install tflint plugins
    - ./tflint --init
    # Run tflint
    - ./tflint -f junit > tflint_report.xml
  artifacts:
    when: always
    reports:
      junit: tflint_report.xml