GitLab CI/CD with Example - Custom Software, Infinite Possibilities.

GitLab’s Continuous Integration and Continuous Deployment (CI/CD) pipelines are a game-changer for modern software development. They allow for automated testing, building, and deploying of code changes, ensuring a smooth and efficient workflow. In this guide, we’ll walk through setting up a basic GitLab CI/CD pipeline with an example, showcasing how you can automate your development process and increase productivity.

Prerequisites

GitLab account
Git repository hosted on GitLab
Basic understanding of Git and GitLab

Step 1: Create a `.gitlab-ci.yml` File

1.1 What is `.gitlab-ci.yml`?

The .gitlab-ci.yml file is where you define the steps of your CI/CD pipeline in YAML format.

1.2 Create `.gitlab-ci.yml`

In your GitLab repository, create a file named .gitlab-ci.yml in the root directory.

1.3 Example `.gitlab-ci.yml`

Here’s a simple example to get started:

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..."

In this example:

We have defined three stages: build, test, and deploy.
Each stage has a corresponding job with a script section. This is where you define the commands to be executed for each job.

Step 2: Define CI/CD Jobs

2.1 Build Job

The build job could be used to compile your code, build Docker images, or perform any pre-deployment tasks.

2.2 Test Job

The test job could run unit tests, integration tests, or any other type of automated tests.

2.3 Deploy Job

The deploy job is responsible for deploying your application to your desired environment, such as staging or production.

Step 3: Commit and Push `.gitlab-ci.yml`

Commit the .gitlab-ci.yml file to your repository and push it to GitLab:

git add .gitlab-ci.yml
git commit -m "Add .gitlab-ci.yml"
git push origin master

Step 4: Set Up CI/CD Pipeline in GitLab

4.1 GitLab CI/CD Configuration

Go to your GitLab repository on the GitLab website.
Navigate to Settings -> CI/CD -> Runners.
Ensure you have shared runners available (either shared or specific to your project).

4.2 Run Pipeline

With the .gitlab-ci.yml file in place, GitLab will automatically detect it and run the pipeline when you push changes.
Go to CI/CD -> Pipelines in your GitLab repository to view the pipeline status and logs.

Step 5: Example with Node.js Application

Let’s create a simple Node.js application and add a CI/CD pipeline for building, testing, and deploying.

5.1 Node.js Application

Create a basic Node.js application:

Create a new directory for your project:

mkdir node-app
cd node-app

Initialize a new Node.js project:

npm init -y

Install a test framework (like Mocha) for testing:

npm install mocha --save-dev

Create a simple app.js file:

// app.js
const sum = (a, b) => a + b;

module.exports = sum;

Create a simple test file test.js:

// test.js
const sum = require('./app');
const assert = require('assert');

describe('Sum function', () => {
  it('should return the sum of two numbers', () => {
    assert.equal(sum(1, 2), 3);
  });
});

5.2 Update `.gitlab-ci.yml`

Now, update the .gitlab-ci.yml file in your repository:

stages:
  - build
  - test
  - deploy

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

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

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

5.3 Commit and Push Changes

Commit your changes and push them to GitLab:

git add .
git commit -m "Add Node.js app and CI/CD pipeline"
git push origin master

5.4 Monitor Pipeline

Go to CI/CD -> Pipelines in your GitLab repository.
You should see the pipeline running.
The build job will install dependencies, the test job will run tests, and the deploy job (in this example, just an echo) will be executed.

Conclusion

This pipeline can be expanded to include more complex build and deployment steps as needed for your projects. GitLab CI/CD offers a wide range of features, such as caching, environment variables, and more, to customize and optimize your pipeline. Explore the GitLab CI/CD documentation for advanced configuration options and best practices.