Infrastructure as code with Terraform and GitLab

Motivation

The Terraform integration features within GitLab enable your GitOps / Infrastructure-as-Code (IaC) workflows to tie into GitLab’s authentication and authorization. These features focus on lowering the barrier to entry for teams to adopt Terraform, collaborate effectively within GitLab, and support Terraform best practices.

GitLab managed Terraform State

Introduced in GitLab 13.0.

Terraform remote backends enable you to store the state file in a remote, shared store. GitLab uses the Terraform HTTP backend to securely store the state files in local storage (the default) or the remote store of your choice.

The GitLab managed Terraform state backend can store your Terraform state easily and securely, and spares you from setting up additional remote resources like Amazon S3 or Google Cloud Storage. Its features include:

  • Supporting encryption of the state file both in transit and at rest.
  • Locking and unlocking state.
  • Remote Terraform plan and apply execution.

To get started with a GitLab-managed Terraform State, there are two different options:

Permissions for using Terraform

In GitLab version 13.1, Maintainer access was required to use a GitLab managed Terraform state backend. In GitLab versions 13.2 and greater, Maintainer access is required to lock, unlock and write to the state (using terraform apply), while Developer access is required to read the state (using terraform plan -lock=false).

Get started using local development

If you plan to only run terraform plan and terraform apply commands from your local machine, this is a simple way to get started:

  1. Create your project on your GitLab instance.
  2. Navigate to Settings > General and note your Project name and Project ID.
  3. Define the Terraform backend in your Terraform project to be:

    terraform {
      backend "http" {
      }
    }
    
  4. Create a Personal Access Token with the api scope.

  5. On your local machine, run terraform init, passing in the following options, replacing <YOUR-PROJECT-NAME>, <YOUR-PROJECT-ID>, <YOUR-USERNAME> and <YOUR-ACCESS-TOKEN> with the relevant values. This command initializes your Terraform state, and stores that state within your GitLab project. This example uses gitlab.com:

    terraform init \
        -backend-config="address=https://gitlab.com/api/v4/projects/<YOUR-PROJECT-ID>/terraform/state/<YOUR-PROJECT-NAME>" \
        -backend-config="lock_address=https://gitlab.com/api/v4/projects/<YOUR-PROJECT-ID>/terraform/state/<YOUR-PROJECT-NAME>/lock" \
        -backend-config="unlock_address=https://gitlab.com/api/v4/projects/<YOUR-PROJECT-ID>/terraform/state/<YOUR-PROJECT-NAME>/lock" \
        -backend-config="username=<YOUR-USERNAME>" \
        -backend-config="password=<YOUR-ACCESS-TOKEN>" \
        -backend-config="lock_method=POST" \
        -backend-config="unlock_method=DELETE" \
        -backend-config="retry_wait_min=5"
    

Next, configure the backend.

Get started using GitLab CI

If you don’t want to start with local development, you can also use GitLab CI to run your terraform plan and terraform apply commands.

Next, configure the backend.

Configure the backend

After executing the terraform init command, you must configure the Terraform backend and the CI YAML file:

  1. In your Terraform project, define the HTTP backend by adding the following code block in a .tf file (such as backend.tf) to define the remote backend:

    terraform {
      backend "http" {
      }
    }
    
  2. In the root directory of your project repository, configure a .gitlab-ci.yaml file. This example uses a pre-built image which includes a gitlab-terraform helper. For supported Terraform versions, see the GitLab Terraform Images project.

    image: registry.gitlab.com/gitlab-org/terraform-images/stable:latest
    
  3. In the .gitlab-ci.yaml file, define some environment variables to ease development. In this example, TF_ROOT is the directory where the Terraform commands must be executed, TF_ADDRESS is the URL to the state on the GitLab instance where this pipeline runs, and the final path segment in TF_ADDRESS is the name of the Terraform state. Projects may have multiple states, and this name is arbitrary, so in this example we will set it to the name of the project, and we will ensure that the .terraform directory is cached between jobs in the pipeline using a cache key based on the state name:

    variables:
      TF_ROOT: ${CI_PROJECT_DIR}/environments/cloudflare/production
      TF_ADDRESS: ${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/terraform/state/${CI_PROJECT_NAME}
    
    cache:
      key: ${CI_PROJECT_NAME}
      paths:
        - ${TF_ROOT}/.terraform
    
  4. In a before_script, change to your TF_ROOT:

    before_script:
      - cd ${TF_ROOT}
    
    stages:
      - prepare
      - validate
      - build
      - deploy
    
    init:
      stage: prepare
      script:
        - gitlab-terraform init
    
    validate:
      stage: validate
      script:
        - gitlab-terraform validate
    
    plan:
      stage: build
      script:
        - gitlab-terraform plan
        - gitlab-terraform plan-json
      artifacts:
        name: plan
        paths:
          - ${TF_ROOT}/plan.cache
        reports:
          terraform: ${TF_ROOT}/plan.json
    
    apply:
      stage: deploy
      environment:
        name: production
      script:
        - gitlab-terraform apply
      dependencies:
        - plan
      when: manual
      only:
        - master
    
  5. Push your project to GitLab, which triggers a CI job pipeline. This pipeline runs the gitlab-terraform init, gitlab-terraform validate, and gitlab-terraform plan commands.

The output from the above terraform commands should be viewable in the job logs.

Example project

See this reference project using GitLab and Terraform to deploy a basic AWS EC2 within a custom VPC.

Output Terraform Plan information into a merge request

Using the GitLab Terraform Report artifact, you can expose details from terraform plan runs directly into a merge request widget, enabling you to see statistics about the resources that Terraform will create, modify, or destroy.

Let’s explore how to configure a GitLab Terraform Report artifact. You can either use a pre-built image which includes a gitlab-terraform helper as above, where gitlab-terraform plan-json outputs the required artifact, or you can configure this manually as follows:

  1. For simplicity, let’s define a few reusable variables to allow us to refer to these files multiple times:

    variables:
      PLAN: plan.cache
      PLAN_JSON: plan.json
    
  2. Install jq, a lightweight and flexible command-line JSON processor.
  3. Create an alias for a specific jq command that parses out the information we want to extract from the terraform plan output:

    before_script:
      - apk --no-cache add jq
      - alias convert_report="jq -r '([.resource_changes[]?.change.actions?]|flatten)|{\"create\":(map(select(.==\"create\"))|length),\"update\":(map(select(.==\"update\"))|length),\"delete\":(map(select(.==\"delete\"))|length)}'"
    
    Note: In distributions that use Bash (for example, Ubuntu), alias statements are not expanded in non-interactive mode. If your pipelines fail with the error convert_report: command not found, alias expansion can be activated explicitly by adding a shopt command to your script:
    before_script:
      - shopt -s expand_aliases
      - alias convert_report="jq -r '([.resource_changes[]?.change.actions?]|flatten)|{\"create\":(map(select(.==\"create\"))|length),\"update\":(map(select(.==\"update\"))|length),\"delete\":(map(select(.==\"delete\"))|length)}'"
    
  4. Define a script that runs terraform plan and terraform show. These commands pipe the output and convert the relevant bits into a store variable PLAN_JSON. This JSON is used to create a GitLab Terraform Report artifact. The Terraform report obtains a Terraform tfplan.json file. The collected Terraform plan report is uploaded to GitLab as an artifact, and is shown in merge requests.

    plan:
      stage: build
      script:
        - terraform plan -out=$PLAN
        - terraform show --json $PLAN | convert_report > $PLAN_JSON
      artifacts:
        reports:
          terraform: $PLAN_JSON
    

    For a full example using the pre-built image, see Example .gitlab-ci.yaml file.

    For an example displaying multiple reports, see .gitlab-ci.yaml multiple reports file.

  5. Running the pipeline displays the widget in the merge request, like this:

    Merge Request Terraform widget

  6. Clicking the View Full Log button in the widget takes you directly to the plan output present in the pipeline logs:

    Terraform plan logs

Example .gitlab-ci.yaml file

image: registry.gitlab.com/gitlab-org/terraform-images/stable:latest

variables:
  TF_ROOT: ${CI_PROJECT_DIR}/environments/cloudflare/production
  TF_ADDRESS: ${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/terraform/state/${CI_PROJECT_NAME}

cache:
  key: ${CI_PROJECT_NAME}
  paths:
    - ${TF_ROOT}/.terraform

before_script:
  - cd ${TF_ROOT}

stages:
  - prepare
  - validate
  - build
  - deploy

init:
  stage: prepare
  script:
    - gitlab-terraform init

validate:
  stage: validate
  script:
    - gitlab-terraform validate

plan:
  stage: build
  script:
    - gitlab-terraform plan
    - gitlab-terraform plan-json
  artifacts:
    name: plan
    paths:
      - ${TF_ROOT}/plan.cache
    reports:
      terraform: ${TF_ROOT}/plan.json

apply:
  stage: deploy
  environment:
    name: production
  script:
    - gitlab-terraform apply
  dependencies:
    - plan
  when: manual
  only:
    - master

Multiple Terraform Plan reports

Starting with 13.2, you can display mutiple reports on the Merge Request page. The reports will also display the artifact: name:. See example below for a suggested setup.

image:
  name: registry.gitlab.com/gitlab-org/gitlab-build-images:terraform
  entrypoint:
    - '/usr/bin/env'
    - 'PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'

cache:
  paths:
    - .terraform

stages:
  - build

.terraform-plan-generation:
  stage: build
  variables:
    PLAN: plan.tfplan
    JSON_PLAN_FILE: tfplan.json
  before_script:
    - cd ${TERRAFORM_DIRECTORY}
    - terraform --version
    - terraform init
    - apk --no-cache add jq
  script:
    - terraform validate
    - terraform plan -out=${PLAN}
    - terraform show --json ${PLAN} | jq -r '([.resource_changes[]?.change.actions?]|flatten)|{"create":(map(select(.=="create"))|length),"update":(map(select(.=="update"))|length),"delete":(map(select(.=="delete"))|length)}' > ${JSON_PLAN_FILE}
  artifacts:
    reports:
      terraform: ${TERRAFORM_DIRECTORY}/${JSON_PLAN_FILE}

review_plan:
  extends: .terraform-plan-generation
  variables:
    TERRAFORM_DIRECTORY: "review/"
  # Review will not include an artifact name

staging_plan:
  extends: .terraform-plan-generation
  variables:
    TERRAFORM_DIRECTORY: "staging/"
  artifacts:
    name: Staging

production_plan:
  extends: .terraform-plan-generation
  variables:
    TERRAFORM_DIRECTORY: "production/"
  artifacts:
    name: Production

Using a GitLab managed Terraform state backend as a remote data source

You can use a GitLab-managed Terraform state as a Terraform data source. To use your existing Terraform state backend as a data source, provide the following details as Terraform input variables:

  • address: The URL of the remote state backend you want to use as a data source. For example, https://gitlab.com/api/v4/projects/<TARGET-PROJECT-ID>/terraform/state/<TARGET-STATE-NAME>.
  • username: The username to authenticate with the data source. If you are using a Personal Access Token for authentication, this is your GitLab username. If you are using GitLab CI, this is 'gitlab-ci-token'.
  • password: The password to authenticate with the data source. If you are using a Personal Access Token for authentication, this is the token value. If you are using GitLab CI, it is the contents of the ${CI_JOB_TOKEN} CI variable.

An example setup is shown below:

  1. Create a file named example.auto.tfvars with the following contents:

    example_remote_state_address=https://gitlab.com/api/v4/projects/<TARGET-PROJECT-ID>/terraform/state/<TARGET-STATE-NAME>
    example_username=<GitLab username>
    example_access_token=<GitLab Personal Acceess Token>
    
  2. Define the data source by adding the following code block in a .tf file (such as data.tf):

    data "terraform_remote_state" "example" {
      backend = "http"
    
      config = {
        address = var.example_remote_state_address
        username = var.example_username
        password = var.example_access_token
      }
    }
    

Outputs from the data source can now be referenced within your Terraform resources using data.terraform_remote_state.example.outputs.<OUTPUT-NAME>.

You need at least developer access to the target project to read the Terraform state.