Terraform Pipelines for Dummies Part 1: Run a Terraform Configuration in GitLabCI

Introduction

Automating infrastructure provisioning with Terraform is nothing for many, but to truly harness IaC power, seamless integration with CI/CD pipelines is key. In this guide, we’ll walk you through the process of setting up and running your Terraform configurations within GitLab CI from a GitHub-imported Repo. This powerful combination not only ensures consistent deployments but also brings version-controlled infrastructure management to the forefront of your development workflow.

This is the first topic of my Terraform pipelines for dummies series that covers pipelined deployments in GitLab, GitHub Actions, AzureDevOps, AWS Catalyst, and GCP Cloud Build. A beautiful excuse to learn CI/CD for Infra bros while having fun. 

I. Importing a GitHub Repo to GitLab

If you have your source repo stored in GitHub (i.e github.com/brokedba/terraform-examples )
There are two ways to do it :

• Option1: Import from GitHub using GitLab UI 

• In your GitLab Portal, click New Project and select the “Import Project” option

• Once you select the import project option, hit “Repository by URL” and fill in the source/target repo details 

• Choose the visibility of the imported project (repo),  and hit Create project.

Note: You could also import the repo by authorizing GitLab to access your GitHub in one click

Option2: Import using Git CLI

• Clone the GitHub repository on your shell

$ git clone https://github.com/brokedba/terraform-examples.git

• Add an SSH public key to your GitLab under GitHub Profile> preference> SSH Key

• Test your connection with your Gitlab from your terminal by specifying the SSH Private Key

brokedba@brokdba:~$ ssh -i ~/.ssh/id_rsa_gitlab -T git@gitlab.com
Welcome to GitLab, @brokedba!

• Create a New GitLab Project in GitLab GUI same as the git repo name “terraform-examples”

• Add GitLab as a Remote repo: adjust the below with your GitLab Namespace 

$ cd terraform-examples $ git remote add origin git@gitlab.com/{Namespace}/terraform-examples.git

• Push to GitLab: this will ask for your GitLab Credentials

$ GIT_SSH_COMMAND="ssh -i ~/.ssh/id_rsa_gitlab" git push -u origin main
remote: Resolving deltas: 100% (733/733), done.
To git@gitlab.com:brokedba/terraform-examples.git
 * [new branch]      main -> main
Branch main set up to track remote branch main from origin.

II. CI/CD Pipeline Authentication Variables

Now that our repo is imported we’ll set the necessary variables for our terraform pipeline. Our target platform will be Oracle Cloud.

1. Under the Project, Click Settings > CI/CD > Variables > Expand > Add Variable

2. Under “Variables”, Click “Expand” and Add your Authentication Variables

For our deployment, we’ll need to set the below variables. GitLab equivalent for secrets is masked variables 

• TF_VAR_Tenancy_OCID: Masked

• TF_VAR_Private_Key_Path: Masked

• TF_VAR_Fingerprint: Masked

• TF_VAR_User_OCID: Masked

• TF_VAR_Compartment_OCID: Masked (where to create the resource )

• TF_VAR_Region

• TF_VAR_SSH_Public_Key: variable of type file, for the vm to be deployed (to contain long text)

• TF_VAR_gitlab_access_token: this token authorizes runners to interact with GitLab. Unlike GitHub, where authentication is automatic through GITHUB_TOKEN, GitLab requires manual setup.

III. Creating the Terraform Pipeline in GitHub

The GitLab CI/CD pipeline config is controlled by a .gitlab-ci.yml file, similar to GitHub Workflow.

• We need to create a CI file in the root directory of our repo based on a template called Terraform.latest.gitlab-ci.yml

Description of the GitLab-ci Content

Each GitLab-CI template allows the abstraction of actions depending on its type. In our case base. GitLab.CI extends all terraform workflow stages. This is different than GitHub actions, with a shorter code footprint.

• 1) The Generic section contains the include which loads templates and the variables

TF_ROOT represents the working directory where our terraform config files reside in my repo.
I have many deployments, but the variable can take any subdirectory I want (Example: launch-instance). Note: the SAST template in the picture was removed later from my include please do the same.       

• 2) Terraform Workflow section where our Terraform Deployment tasks are performed (Example: Init, Plan and Deploy)

After we declared the stage names and defined the same in a sequence as described below.

1. 1. FMT – For formatting the Terraform config.

   2. Validate – Validation of Code

   3. Build – Run Terraform Plan

   4. Deploy – Executes Terraform apply command. Then save the state file as an artifact

   5. Cleanup – Load the artifact (state file) and destroy the resource

Each stage uses the keyword “extends” with .terraform:*  that references a function in the template

VI. Executing the Terraform Pipeline

Now that we have both the project (repo), the variables, and the pipeline defined let’s run it and monitor the workflow.

• Go to your Project> Build > Pipeline and Click Run Pipeline

• DEPLOY: Both the validate and build (TF Plan) stages are now done, the pipeline waits for a manual deploy

• Once run, you can check the logs while our web server is being deployed in the Oracle Cloud Platform

• If we check the console, we’ll see that the web server is now up and running, ready to take requests

• DESTROY: After a successful deployment, all looks good, we can now clean by tearing down our resources

• Notice how the cleanup job reused the state file, loaded from the artifact to destroy the webserver

Final Pipeline Status

Once complete we can see the status and the time it took to finish the pipeline (FMT had just a minor warning) 

V. GitLab Experience “Hits and Misses”

There are pros and tread offs about using GitLab over GitHub actions, here’s a few to consider 

The Advantages (Pros)

• GitLab is Open source but still more secure than GitHub

• I love how GitLab allows us to pause a pipeline stage using the manual job option that GitHub doesn’t have

• GitLab has a lot of templates available for different frameworks unlike GitHub actions 3rd-party marketplace

• GitLab CI offers better reporting and auditing capabilities, for tracking/analyzing workflow performance

• Full of other features: child pipelines, dynamic pipeline generation, very flexible conditionals, composable pipeline definitions, security, merge trains, and code review

The Disadvantages (Cons)

• GitLab lacks GitHub’s massive popularity/support in the community (fewer blogs/StackOverflow posts)

• GitLab supports only one CI workflow file (gitlab-ci.yaml) per repository, whereas GitHub allows multiple

• GitLab UI lacks Auto-refresh of the pipeline/job status forcing you to refresh the browser unlike in GitHub

The Conclusion:

• We just showed a simple pipeline automating the whole workflow of a terraform deployment in OCI

• We also leveraged GitLab’s unique manual job option for pausing pipeline stages which is rare elsewhere

• GitLab’s singular approach relies on a rich built-in template library instead of a public Marketplace

• I tried to share a few bits in terms of experience but there are tons of articles comparing GitLab and GitHub

• My demo didn’t cover event triggers via rules(CI_PIPELINE_SOURCE), but you can learn more here

• I also used artifacts to save a state file but it’s recommended to use GitLab managed remote state instead

• Hope this helps! Next, I’ll dive into GitHub Actions terraform Multicloud pipelines using OIDC.