GitLab CI/CD Tutorial [25 Practical Articles]

In this article we are going to cover GitLab CI/CD Tutorial, GitLab Basic Tutorial, Contineous Integration (CI) with GitLab, SonarQube Integration with GitLab CI, Build & Use Custom Docker Images in your GitLab CI/CD pipeline,Contineous Deployments (CD) with GitLab.

Table of Contents

What is GitLab ?

GitLab is a web-based DevOps platform that provides a complete set of tools for software development, version control, continuous integration/continuous deployment (CI/CD), and collaboration. It is a popular alternative to GitHub and offers a more comprehensive set of features for organizations looking to manage their entire software development lifecycle in one platform.

Features of GitLab

Git Repository Management: GitLab provides hosting for Git repositories, allowing developers to store, manage, and collaborate on their codebase using Git version control.
Issue Tracking: GitLab includes an issue tracking system to manage and prioritize tasks, bugs, and feature requests during the development process.
Continuous Integration/Continuous Deployment (CI/CD): GitLab has built-in CI/CD capabilities that enable developers to automate the build, test, and deployment processes for their applications.
Code Review: GitLab facilitates code collaboration and review through merge requests (similar to pull requests in GitHub) and offers features for code commenting and discussion.
Wiki and Documentation: GitLab provides a wiki feature for documenting projects, making it easier for teams to maintain project-related documentation.
Container Registry: GitLab includes a container registry to store Docker images, making it convenient for projects that use containerization for deployment.
Security and Code Analysis: GitLab offers security scanning and code analysis tools to help identify vulnerabilities and improve code quality.
Integration and Extensibility: GitLab supports integration with various third-party tools and services, allowing teams to customize their development workflow according to their needs.
Enterprise Edition: GitLab offers an Enterprise Edition that includes additional features and support tailored for larger organizations and enterprise use cases.

GitLab provides both cloud-hosted (GitLab.com) and self-hosted versions, which can be deployed on-premises or on your own servers.

Please note that developments may have occurred after my last update, and it’s always a good idea to visit the official GitLab website or documentation for the most current information.

GitLab Architecture

Please find high level diagram of GitLab if you want to know more then visit GitLab Official site

GitLab CI/CD Tutorial [25 Practical Articles] 1

GitLab’s architecture is designed to be flexible, scalable, and capable of supporting various deployment options, including GitLab.com’s cloud-hosted service and self-hosted instances. The architecture consists of several components that work together to provide a complete DevOps platform. Keep in mind that there might have been updates or changes to the architecture since then, so it’s best to refer to the official GitLab documentation for the latest details. Here’s an overview of the typical GitLab architecture:

Web Application: The Web Application is the user interface that developers and team members interact with via their web browsers. It provides access to various features like code repositories, issue tracking, merge requests, CI/CD pipelines, and more. The Web Application is built using Ruby on Rails and interacts with other components through APIs.
Database: GitLab relies on a relational database to store and manage project data, including information related to users, projects, issues, merge requests, CI/CD pipelines, and other settings. By default, GitLab uses PostgreSQL as its database, but it also supports MySQL and other database systems.
Git Repository Management: GitLab handles Git repository management, storing the actual code and version history. GitLab uses the standard Git protocol for interacting with Git repositories, and repositories can be stored on the file system or, in some setups, an object storage system like Gitaly or GitLab Pages.
Background Workers: GitLab uses background workers to handle time-consuming and resource-intensive tasks asynchronously. These workers are responsible for processing jobs related to continuous integration, continuous deployment, email notifications, and other background activities.
Object Storage (Gitaly): In larger GitLab installations, Git repositories might be stored on a separate object storage system like Gitaly. Gitaly is a custom-built Git RPC service that enables distributed and scalable storage for Git repositories.
CI/CD Runners: GitLab CI/CD relies on runners to execute CI/CD jobs. Runners can be either shared runners provided by GitLab.com or dedicated runners installed on self-hosted instances. Runners execute the defined CI/CD pipelines and report the results back to GitLab.
Container Registry: GitLab provides an integrated container registry that allows you to store Docker images within GitLab. The container registry is used to manage and distribute container images used in CI/CD pipelines or other parts of your infrastructure.
Load Balancer: In high-availability setups, GitLab instances often use a load balancer to distribute incoming web requests across multiple nodes, ensuring high performance and fault tolerance.
Cache: GitLab uses caching mechanisms to improve performance and reduce the load on the database. Caches are used to store frequently accessed data, reducing the need for repeated database queries.
Reverse Proxy (Nginx, Apache, etc.): GitLab instances typically utilize a reverse proxy server like Nginx or Apache to handle incoming web requests, improve security, and provide SSL termination.

These are the primary components of a typical GitLab architecture. However, the setup and configuration can vary depending on whether it’s a small-scale deployment or a large-scale enterprise installation. For more detailed information and guidance on setting up a GitLab instance, refer to the official GitLab documentation and architectural guides.

What is GitLab CI/CD Pipeline ?

GitLab CI/CD (Continuous Integration/Continuous Deployment) is a set of tools and practices provided by GitLab, a web-based platform for version control and collaboration. It allows developers to automate and streamline the process of building, testing, and deploying software applications.

The CI/CD pipeline in GitLab refers to the series of steps that code changes go through from the point they are committed to a repository to the point they are deployed and made available to users.

Here’s a breakdown of what GitLab CI/CD pipeline involves:

Version Control: Developers commit their code changes to a Git repository hosted on GitLab.
Continuous Integration (CI):
- Upon code commits, GitLab automatically triggers CI jobs.
- CI jobs include tasks such as building the application, running tests, and performing code analysis.
- The goal is to catch integration issues early and ensure that the codebase remains stable.
Continuous Deployment (CD):
- After successful CI, the CD phase begins.
- CD involves automating the deployment of code changes to various environments (staging, production, etc.).
- Deployment can include tasks like deploying to servers, updating databases, and configuring services.
Pipeline Configuration:
- The pipeline is defined using a .gitlab-ci.yml file in the repository.
- This YAML file defines the different stages, jobs, and steps in the pipeline.
- It specifies which tasks should run in parallel, which need to be sequential, and how the stages are organized.
Artifacts and Cache:
- CI jobs can generate artifacts (compiled binaries, test reports, etc.) that are saved for later use.
- Caching can be used to speed up the build process by storing dependencies between runs.
Monitoring and Notifications:
- GitLab provides dashboards and logs to monitor the progress of CI/CD pipelines.
- Notifications can be configured to alert developers about pipeline status or failures.
Deployment Strategies:
- GitLab supports various deployment strategies such as rolling updates, blue-green deployments, and canary releases.
- These strategies help ensure smooth deployments without disrupting user experience.

The GitLab CI/CD pipeline offers automation and repeatability, reducing manual intervention and the risk of human error during the software development lifecycle. It encourages a culture of continuous improvement by promoting frequent code integration, automated testing, and seamless deployment. This ultimately leads to faster delivery of features and improvements to end-users while maintaining code quality and stability.