Infrastructure as code with Terraform and GitLab

GitLab managed Terraform State

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:

Use a local machine.
Use GitLab CI.

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:

Create your project on your GitLab instance.
Navigate to {settings} Settings > General and note your Project name and Project ID.
Define the Terraform backend in your Terraform project to be:
```
terraform {
  backend "http" {
  }
}
```
Create a Personal Access Token with the api scope. The Terraform backend is restricted to users with Maintainer access to the repository.

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:

CAUTION: Important: The Terraform backend is restricted to users with Maintainer access to the repository.

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" {
  }
}
```

In the root directory of your project repository, configure a .gitlab-ci.yaml file. This example uses a pre-built image:

image:
  name: hashicorp/terraform:light
  entrypoint:
    - '/usr/bin/env'
    - 'PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'

In the .gitlab-ci.yaml file, define some environment variables to ease development. In this example, GITLAB_TF_ADDRESS is the URL of the GitLab instance where this pipeline runs, and TF_ROOT is the directory where the Terraform commands must be executed:
```
variables:
  GITLAB_TF_ADDRESS: ${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/terraform/state/${CI_PROJECT_NAME}
  TF_ROOT: ${CI_PROJECT_DIR}/environments/cloudflare/production

cache:
  paths:
    - .terraform
```

In a before_script, pass a terraform init call containing configuration parameters corresponding to variables required by the HTTP backend:

before_script:
  - cd ${TF_ROOT}
  - terraform --version
  - terraform init -backend-config="address=${GITLAB_TF_ADDRESS}" -backend-config="lock_address=${GITLAB_TF_ADDRESS}/lock" -backend-config="unlock_address=${GITLAB_TF_ADDRESS}/lock" -backend-config="username=gitlab-ci-token" -backend-config="password=${CI_JOB_TOKEN}" -backend-config="lock_method=POST" -backend-config="unlock_method=DELETE" -backend-config="retry_wait_min=5"

stages:
  - validate
  - build
  - test
  - deploy

validate:
  stage: validate
  script:
    - terraform validate

plan:
  stage: build
  script:
    - terraform plan
    - terraform show

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

Push your project to GitLab, which triggers a CI job pipeline. This pipeline runs the terraform init, terraform validate, and 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:

For simplicity, let's define a few reusable variables to allow us to refer to these files multiple times:
```
variables:
  PLAN: plan.tfplan
  PLAN_JSON: tfplan.json
```
Install jq, a lightweight and flexible command-line JSON processor.

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)}'"

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:
    name: plan
    paths:
      - $PLAN
    reports:
      terraform: $PLAN_JSON
```
For a full example, see Example .gitlab-ci.yaml file.
Running the pipeline displays the widget in the merge request, like this:
Clicking the View Full Log button in the widget takes you directly to the plan output present in the pipeline logs:

Example `.gitlab-ci.yaml` file

image:
  name: hashicorp/terraform:light
  entrypoint:
    - '/usr/bin/env'
    - 'PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'

# Default output file for Terraform plan
variables:
  GITLAB_TF_ADDRESS: ${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/terraform/state/${CI_PROJECT_NAME}
  PLAN: plan.tfplan
  PLAN_JSON: tfplan.json
  TF_ROOT: ${CI_PROJECT_DIR}

cache:
  paths:
    - .terraform

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)}'"
  - cd ${TF_ROOT}
  - terraform --version
  - terraform init -backend-config="address=${GITLAB_TF_ADDRESS}" -backend-config="lock_address=${GITLAB_TF_ADDRESS}/lock" -backend-config="unlock_address=${GITLAB_TF_ADDRESS}/lock" -backend-config="username=${GITLAB_USER_LOGIN}" -backend-config="password=${GITLAB_TF_PASSWORD}" -backend-config="lock_method=POST" -backend-config="unlock_method=DELETE" -backend-config="retry_wait_min=5"

stages:
  - validate
  - build
  - deploy

validate:
  stage: validate
  script:
    - terraform validate

plan:
  stage: build
  script:
    - terraform plan -out=$PLAN
    - terraform show --json $PLAN | convert_report > $PLAN_JSON
  artifacts:
    name: plan
    paths:
      - ${TF_ROOT}/plan.tfplan
    reports:
      terraform: ${TF_ROOT}/tfplan.json

# Separate apply job for manual launching Terraform as it can be destructive
# action.
apply:
  stage: deploy
  environment:
    name: production
  script:
    - terraform apply -input=false $PLAN
  dependencies:
    - plan
  when: manual
  only:
    - master