Getting started with GitLab: Understanding CI/CD

Welcome to our "Getting started with GitLab" series, where we help newcomers get familiar with the GitLab DevSecOps platform.

Imagine a workflow where every code change is automatically built, tested, and deployed to your users. That's the power of Continuous Integration/Continuous Delivery (CI/CD)! CI/CD helps you catch bugs early, ensures code quality, and delivers software faster and more frequently.

What is CI/CD?

• Continuous Integration is a development practice where developers integrate code changes into a shared repository frequently, preferably several times a day. Each integration is then verified by an automated build and test process, allowing teams to detect problems early.
• Continuous Delivery extends CI by automating the release pipeline, ensuring that your code is always in a deployable state. You can deploy your application to various environments (e.g., staging, production) with a single click or automatically.
• Continuous Deployment takes it a step further by automatically deploying every successful build to production. This requires a high degree of confidence in your automated tests and deployment process.

Why GitLab CI/CD?

GitLab CI/CD is a powerful, integrated system that comes built-in with GitLab. It offers a seamless experience for automating your entire software development lifecycle. With GitLab CI/CD, you can:

• Automate everything: Build, test, and deploy your applications with ease.
• Catch bugs early: Detect and fix errors before they reach production.
• Get faster feedback: Receive immediate feedback on your code changes.
• Improve collaboration: Work together more effectively with automated workflows.
• Accelerate delivery: Release software faster and more frequently.
• Reduce risk: Minimize deployment errors and rollbacks.

The elements of GitLab CI/CD

• .gitlab-ci.yml: This YAML file, located in your project's root directory, defines your CI/CD pipeline, including stages, jobs, and runners.
• GitLab Runner: This agent executes your CI/CD jobs on your infrastructure (e.g. physical machines, virtual machines, Docker containers, or Kubernetes clusters).
• Stages: Stages define the order of execution for your jobs (e.g. build, test, and deploy).
• Jobs: Jobs are individual units of work within a stage (e.g. compile code, run tests, and deploy to staging).

Setting up GitLab CI

Getting started with GitLab CI is simple. Here's a basic example of a .gitlab-ci.yml file:

stages:
  - build
  - test
  - deploy

build_job:
  stage: build
  script:
    - echo "Building the application..."

test_job:
  stage: test
  script:
    - echo "Running tests..."

deploy_job:
  stage: deploy
  script:
    - echo "Deploying to production..."
  environment:
    name: production

This configuration defines three stages: "build," "test," and "deploy." Each stage contains a job that executes a simple script.

CI/CD configuration examples

Let's explore some more realistic examples.

Building and deploying a Node.js application

The pipeline definition below outlines using npm to build and test a Node.js application and dpl to deploy the application to Heroku. The deploy stage of the pipeline makes use of GitLab CI/CD variables, which allow developers to store sensitive information (e.g. credentials) and securely use them in CI/CD processes. In this example, an API key to deploy to Heroku is stored under the variable key name $HEROKU_API_KEY used by the dpl tool.

stages:
  - build
  - test
  - deploy

build:
  stage: build
  image: node:latest
  script:
    - npm install
    - npm run build

test:
  stage: test
  image: node:latest
  script:
    - npm run test

deploy:
  stage: deploy
  image: ruby:latest
  script:
    - gem install dpl
    - dpl --provider=heroku --app=$HEROKU_APP_NAME --api-key=$HEROKU_API_KEY

Deploying to different environments (staging and production)

GitLab also offers the idea of Environments with CI/CD. This feature allows users to track deployments from CI/CD to infrastructure targets. In the example below, the pipeline adds stages with an environment property for a staging and production environment. While the deploy_staging stage will always run its script, the deploy_production stage requires manual approval to prevent accidental deployment to production.

stages:
  - build
  - test
  - deploy_staging
  - deploy_production

build:
  # ...

test:
  # ...

deploy_staging:
  stage: deploy_staging
  script:
    - echo "Deploying to staging..."
  environment:
    name: staging

deploy_production:
  stage: deploy_production
  script:
    - echo "Deploying to production..."
  environment:
    name: production
  when: manual  # Requires manual approval

GitLab Auto DevOps

GitLab Auto DevOps simplifies CI/CD by providing a pre-defined configuration that automatically builds, tests, and deploys your applications. It leverages best practices and industry standards to streamline your workflow.

To enable Auto DevOps:

1. Go to your project's Settings > CI/CD > General pipelines.
2. Enable the Auto DevOps option.

Auto DevOps automatically detects your project's language and framework and configures the necessary build, test, and deployment stages. You don’t even need to create a .gitlab-ci.yml file.

CI/CD Catalog

The CI/CD Catalog is a list of projects with published CI/CD components you can use to extend your CI/CD workflow. Anyone can create a component project and add it to the CI/CD Catalog or contribute to an existing project to improve the available components. You can find published components in the CI/CD Catalog on GitLab.com.

Tutorial: How to set up your first GitLab CI/CD component

CI templates

You can also create your own CI templates to standardize and reuse CI/CD configurations across multiple projects. This promotes consistency and reduces duplication.

To create a CI template:

1. Create a .gitlab-ci.yml file in a dedicated project or repository.
2. Define your CI/CD configuration in the template.
3. In your project's .gitlab-ci.yml file, use the include keyword to include the template.

Take your development to the next level

GitLab CI/CD is a powerful tool that can transform your development workflow. By understanding the concepts of CI/CD, configuring your pipelines, and leveraging features like Auto DevOps, the CI/CD Catalog, and CI templates, you can automate your entire software development lifecycle and deliver high-quality software faster and more efficiently.

Want to take your learning to the next level? Sign up for GitLab University courses. Or you can get going right away with a free 60-day trial of GitLab Ultimate.

"Getting Started with GitLab" series

Check out more articles in our "Getting Started with GitLab" series:

• How to manage users
• How to import your projects to GitLab
• Mastering project management
• Automating Agile workflows with the gitlab-triage gem
• Working with CI/CD variables