Prerequisite Concepts

With the advancement of software development methods, the use of Continuous Integration (CI) and Continuous Deployment (CD) has become increasingly common. These approaches, by enabling rapid cycles, ensuring code quality, and supporting integrated deployment, help development teams deliver high-quality software at scale.

In this context, GitLab Runner plays a key role; this tool is responsible for executing the CI/CD pipeline defined in the GitLab configuration file (.gitlab-ci.yml). By automating tasks such as build, test, and deployment of code, GitLab Runner allows developers to focus on writing code without being bogged down by the complexities of deployment processes.

As an example, suppose you want to write clean code and don’t want to manually check each time whether all function naming conventions are correctly followed; in such cases, you can use GitLab Runner to check these aspects.

An environment specifies a stage of development; it is used to define the scope of execution for a job. For instance, environments like build, test, and deploy.

A job is a piece of code for execution that is defined in an environment and will run in that specific environment.

A runner in GitLab is a process that executes various jobs.

Below is a sample gitlab-ci.yml file with explanations:

stages:
  - build
  - test
  - deploy

build_job:
  stage: build
  script:
    - echo "Building the app..."
    - npm install
    - npm run build
  artifacts:
    paths:
      - dist/

test_job:
  stage: test
  script:
    - echo "Running tests..."
    - npm test
  needs: [build_job]

deploy_staging:
  stage: deploy
  script:
    - echo "Deploying to staging..."
    - scp dist/* user@staging-server:/path/to/staging
    - ssh user@staging-server "restart-staging-service"
  environment:
    name: staging
    url: https://staging.example.com
  rules:
    - if: '$CI_COMMIT_BRANCH == "develop"'

A runner executes the defined file and, based on the environment specified with the environment tag, automatically starts the relevant job defined in the script section. This capability allows various tasks in different development stages (such as testing, building, deployment, etc.) to be executed in a targeted manner aligned with the intended stage.