How To Build CI/CD Pipeline in GitLab

Introduction

In modern software development, automation is crucial for efficiency and reliability. CI/CD (Continuous Integration/Continuous Deployment) pipelines help automate the entire process of building, testing, and deploying applications. GitLab CI/CD provides a powerful built-in pipeline mechanism to streamline this workflow.

This guide will walk you through creating a CI/CD pipeline using GitLab, covering setup, writing a .gitlab-ci.yml configuration file, defining build, test, and deployment stages, and best practices.

What is GitLab?
Understanding CI/CD Pipelines
Prerequisites
Setting Up a CI/CD Pipeline in GitLab
- Creating a GitLab Account
- Checking for GitLab Runners
- Creating or Importing a Project
Writing a .gitlab-ci.yml File
- Build Stage
- Test Stage
- Deploy Stage
Optimizing the Pipeline
Monitoring Pipelines in GitLab
Conclusion

🔗 Official Documentation:

1. What is GitLab?

GitLab is an all-in-one DevOps platform that enables developers to store, manage, and collaborate on code efficiently. It includes built-in CI/CD tools to automate the software development lifecycle, from code integration to deployment.

Key Features of GitLab CI/CD:
✔ Automated testing and deployment
✔ Supports Docker-based builds
✔ Integration with Kubernetes and cloud providers
✔ Customizable pipelines with .gitlab-ci.yml

2. Understanding CI/CD Pipelines

A CI/CD pipeline is a series of automated steps that manage the software development lifecycle, including:

Continuous Integration (CI): Automatically testing and integrating code changes.
Continuous Deployment (CD): Deploying software updates to production.

CI/CD Pipeline Workflow in GitLab:

1️⃣ Code Changes → Developer pushes code to GitLab.
2️⃣ CI/CD Pipeline Triggers → GitLab starts build, test, and deployment stages.
3️⃣ Build Stage → Compiles code and prepares artifacts.
4️⃣ Test Stage → Runs automated tests to ensure quality.
5️⃣ Deploy Stage → Deploys changes to production.

3. How To Build CI/CD Pipeline in GitLab – Prerequisites

Before creating a GitLab CI/CD pipeline, ensure you have:

✅ A GitLab Account – Sign up at GitLab.com
✅ Basic Git Knowledge – Git Documentation
✅ A GitLab Project – Either create a new project or import an existing one.
✅ GitLab Runner Installed – If using GitLab locally, install a GitLab Runner.

4. Setting Up a CI/CD Pipeline in GitLab

Step 1: Creating a GitLab Account

If you haven’t already, create a GitLab account at GitLab.com.

Step 2: Checking for Runners

Runners execute CI/CD jobs. To check available runners:

Navigate to Settings → CI/CD → Runners
If using GitLab’s hosted service, a runner should be active.
If self-hosting, install a GitLab Runner (Installation Guide).

Step 3: Creating or Importing a Project

Go to GitLab Dashboard
Click New Project → Import Project (for GitHub imports)

5. Writing a `.gitlab-ci.yml` File

The .gitlab-ci.yml file defines the CI/CD pipeline and should be placed in the root directory of your project.

Step 1: Creating the File

In your GitLab project:
1️⃣ Click the + button → New File
2️⃣ Name it .gitlab-ci.yml

Step 2: Defining the Pipeline Stages

stages:
  - build
  - test
  - deploy

This ensures GitLab runs tasks in the order of build → test → deploy.

Step 3: Build Stage

build-job:
  image: node
  stage: build
  script:
    - npm install
    - npm run build
  artifacts:
    paths:
      - "dist/"

🔹 Uses the Node.js image to install dependencies and build the project.
🔹 Stores the dist/ folder for later stages.

Step 4: Test Stage

test-html:
  stage: test
  dependencies: []
  script:
    - npm install --save-dev htmlhint
    - npx htmlhint "dist/**/*.html"

🔹 Runs HTML linting to check for errors.
🔹 Defines dependencies: [] so this job runs independently.

Step 5: Deploy Stage

deploy:
  stage: deploy
  image: busybox
  dependencies:
    - build-job
  script:
    - mv dist/ public/
  artifacts:
    paths:
      - "public/"
  rules:
    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH

🔹 Deploys the built files to GitLab Pages or another hosting provider.
🔹 Uses a lightweight BusyBox image for efficiency.
🔹 Ensures deployment only happens on the main branch.

6. Optimizing the Pipeline

To avoid duplication, we define reusable jobs:

default:
  image: node

.standard-rules:
  rules:
    - if: $CI_PIPELINE_SOURCE == 'merge_request_event'
    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH

🔹 default: sets a global Node.js image for all jobs.
🔹 .standard-rules: defines conditions for triggering jobs.

7. Monitoring Pipelines in GitLab

To track your CI/CD pipeline:
1️⃣ Go to Project Dashboard
2️⃣ Click Build → Pipelines
3️⃣ View the status of each job (Success ✅ or Failure ❌)

🔗 Monitoring CI/CD Pipelines

8. Conclusion

Using GitLab’s CI/CD pipeline, we can automate the build, test, and deploy workflow efficiently. This approach reduces manual errors, saves time, and ensures software is always in a deployable state.

Key Takeaways:

✔ GitLab CI/CD automates building, testing, and deployment.
✔ The .gitlab-ci.yml file defines pipeline stages and jobs.
✔ GitLab Runners execute CI/CD jobs efficiently.
✔ Monitoring pipelines helps track build status and errors.