What happens after GitLab receives the code?

GitLab, upon receiving code (usually via git push), initiates a process depending on the project settings:

1. Webhooks: When new code arrives, GitLab can notify external systems (such as CI/CD servers, project management systems) by sending HTTP requests. This acts as a trigger for further actions.

2. CI/CD pipeline: If a .gitlab-ci.yml file is configured in the project, GitLab Runner starts the CI/CD pipeline. This process includes:

   • Syntax check of the .gitlab-ci.yml file.
   • Creating jobs based on the definitions in the yml file.
   • Assigning jobs to available runners.
   • The runner receives jobs, downloads the repository's source code.
   • Executes commands specified for each job (build, test, deploy, etc.).
   • Saves artifacts (built applications, test reports) and log files.
   • Sends the status of job execution back to GitLab.

   Example structure of .gitlab-ci.yml:

   stages:
     - build
     - test
     - deploy
   
   build_job:
     stage: build
     script:
       - echo "Building the application..."
       - make build
   
   test_job:
     stage: test
     script:
       - echo "Running tests..."
       - make test
   
   deploy_job:
     stage: deploy
     script:
       - echo "Deploying the application..."
       - make deploy
     only:
       - main  # Trigger only on push to the main branch
   

3. Automatic actions: GitLab can perform other automatic actions:

   • Creating Merge Requests (when pushing to a branch other than the target branch).
   • Updating the status of Merge Requests (if it exists).
   • Running security scans (if configured).
   • Automatically closing or linking tasks (via keywords in commits or Merge Request descriptions).

4. Notification system: GitLab sends notifications to users via email or other channels (Slack, Mattermost) if they are subscribed to repository events (new commits, pipeline statuses, comments).

5. Repository data update: Internally, GitLab updates data about repositories, branches, tags, and commit history.

Overall, the process aims to integrate new code into the overall workflow, automate build, testing, and possibly deployment, as well as notify interested parties.