Mastering GitLab CI/CD: From Basics to Advanced Pipelines

GitLab CI/CD is an integrated tool in GitLab that enables continuous integration (CI), continuous delivery (CD), and continuous deployment. It works by pushing small code changes to a Git repository, automatically running scripts to build, test, and verify code before merging into the main branch.

Core Concepts

Continuous Integration: automatically builds and tests each change.

Continuous Delivery: extends CI by preparing deployments that can be manually triggered.

Continuous Deployment: fully automates deployment without manual steps.

The process is defined in a .gitlab-ci.yml file at the repository root, which GitLab Runner executes.

Basic Configuration

A simple pipeline consists of jobs grouped into stages (e.g., build, test, deploy). Example:

before_script:
  - apt-get install rubygems ruby-dev -y
run-test:
  script:
    - ruby --version 6

This defines a before_script to install dependencies and a

run-test</job> that prints the Ruby version. The pipeline runs on each push.</p>
<h2>Runner Setup</h2>
<p>Runners execute the jobs defined in <code>.gitlab-ci.yml

. They can be virtual machines, Docker containers, or physical machines and communicate with GitLab via API. After configuring a runner, you can view job status in the Pipelines > Jobs page.

Advanced Features

GitLab CI/CD supports visual pipelines, job logs, and rollback capabilities. It also integrates with Auto DevOps, which provides predefined CI/CD configurations for automatic detection, building, testing, deployment, and monitoring.

Auto DevOps can deploy projects to Kubernetes clusters (e.g., GKE) with minimal configuration, handling Helm, Ingress, and Prometheus setup automatically.

Typical CI/CD Workflow

Define .gitlab-ci.yml with jobs and scripts.

Push the file to the remote repository.

GitLab detects the file and triggers pipelines via the Runner.

Monitor pipeline stages (build → test → deploy → performance test) and view environments.

Use UI buttons to open the deployed app, view Prometheus metrics, or open a web terminal.

Example: Deploying a Spring Boot Application

image: "java:8"
stages:
  - build
  - deploy
before_script:
  - chmod +x mvnw
build:
  stage: build
  script:
    - ./mvnw package
  artifacts:
    paths:
      - target/demo-0.0.1-SNAPSHOT.jar
production:
  stage: deploy
  script:
    - curl --location "https://cli.run.pivotal.io/stable?release=linux64-binary&source=github" | tar zx
    - ./cf login -u $CF_USERNAME -p $CF_PASSWORD -a api.run.pivotal.io
    - ./cf push
  only:
    - master

This example defines a build stage that packages a Spring Boot JAR and a deployment stage that logs into Cloud Foundry and pushes the app.

Additional Capabilities

Auto DevOps for end‑to‑end pipelines.

Package management with Container Registry, NPM Registry, Maven Repository, and Conan Repository.

Release management, feature flags, canary deployments, and GitLab Pages.

Security testing reports and vulnerability scanning.

Overall, GitLab CI/CD provides a comprehensive, script‑driven workflow for automating software delivery from code commit to production deployment.