GitLab is a web-based Git repository management tool, and also a complete CI/CD solution. It provides many built-in CI/CD tools that let software developers easily integrate continuous integration, continuous delivery, automated testing, and other workflows. This article covers the concepts behind GitLab CI/CD, its advantages, and how to use it.

1. What Is GitLab CI/CD?

GitLab CI/CD is an automation tool that automates every stage of software development, from building and testing to deployment and release.

CI stands for Continuous Integration — integrating different pieces of code together and running builds, tests, and so on. CD stands for Continuous Deployment — deploying finished code to a real production environment. The main goal of CI/CD is to automate the software delivery process so developers can ship high-quality software faster. GitLab CI/CD is a component of GitLab that lets developers integrate CI/CD workflows directly into their codebase.

2. Advantages of GitLab CI/CD

GitLab CI/CD has many advantages — here are a few:

  • Simple and easy to use: GitLab CI/CD’s syntax is simple and easy to understand, letting developers easily understand and configure CI/CD workflows.
  • Highly customizable: GitLab CI/CD can be highly customized for different needs. It supports many programming languages and frameworks, and provides many built-in tools and plugins.
  • Strong integration: GitLab CI/CD integrates with other GitLab features, such as code management, issue tracking, and merge requests, letting developers manage their software projects more efficiently.
  • Cross-platform: GitLab CI/CD can run on any platform, such as Linux, Windows, macOS, and so on.
  • Easy to extend: GitLab CI/CD provides a rich API and plugin interface, letting developers easily extend and integrate their CI/CD workflows.

3. How to Use GitLab CI/CD

Using GitLab CI/CD can be broken into the following steps:

  1. Configure the .gitlab-ci.yml file.
  2. Configure a runner.

3.1 Configuring the .gitlab-ci.yml file

.gitlab-ci.yml is GitLab CI/CD’s configuration file — it defines the tasks and operations to run as part of the CI/CD workflow. In GitLab, you can create a file named .gitlab-ci.yml at the root of the repository. This file can contain one or more jobs, each representing a task to run as part of the CI/CD workflow.

3.1.1 Stages

A GitLab CI/CD workflow is usually made up of several stages. Each stage consists of one or more jobs, which can run in a certain order. In the .gitlab-ci.yml file, you can use the stages keyword to define the stages of the workflow, as shown below:

stages:
  - build
  - test
  - deploy

In this example, we’ve defined three stages: build, test, and deploy.

3.1.2 Jobs

Within each stage, you can define one or more jobs to run different tasks. In the .gitlab-ci.yml file, you can use the jobs keyword to define jobs, as shown below:

build:
  stage: build
  script:
    - npm install
    - npm run build
  artifacts:
    paths:
      - dist/
test:
  stage: test
  script:
    - npm install
    - npm run test
  needs: [build]
deploy:
  stage: deploy
  script:
    - deploy.sh
  needs: [test]

In this example, we’ve defined three jobs: build, test, and deploy. Each job has a stage attribute specifying which stage it belongs to. The script attribute specifies the commands the job needs to run, the artifacts attribute defines the build artifacts the job produces, and the needs attribute specifies the job’s prerequisites.

In this example, the build job installs dependencies and builds the project, the test job runs tests, and the deploy job deploys the project. The test job depends on the build job finishing first, and the deploy job depends on the test job finishing first.

3.1.3 Variables

The .gitlab-ci.yml file can also define variables to pass parameters or configuration information through the CI/CD workflow. You can use the variables keyword to define variables, as shown below:

variables:
  DATABASE_URL: postgres://user:password@localhost/mydatabase

This example defines a variable named DATABASE_URL containing the database connection info. Within the CI/CD workflow, this variable can be referenced as $DATABASE_URL.

3.2 Configuring a runner

A runner is the machine that actually does the work — GitLab CI/CD needs a runner to execute the CI/CD workflow. You can use GitLab’s own shared runners, or set up your own. In GitLab, runners can be managed under Settings → CI/CD → Runners. See GitLab’s official documentation for detailed installation and configuration instructions.

3.3 Actually triggering it

Note that when using GitLab CI/CD, you need to handle sensitive information carefully — such as database passwords and API keys — to avoid leaking important information. You can use the CI/CD variables and encryption mechanisms GitLab provides to protect sensitive information.

4. Summary

This article covered the concepts behind GitLab CI/CD and how to use the .gitlab-ci.yml file to define a CI/CD workflow. We looked at how to define stages, jobs, and variables, and covered some commonly used CI/CD features such as artifacts and dependencies. Finally, we briefly covered how to configure a runner.