Cloud Computing – Lab 06: CI/CD and Services' Resilience

Master in Computer Engineering – Mobile Computing (2025/2026)

Date: 7th April 2026

Worksheet Briefing

Based on the previous lab's source code, in this worksheet we will create a CI/CD pipeline to build and push Docker images to the GitHub Container Registry (GHCR) using GitHub Actions. In the last part, we will ensure services resilience by adding a retry and fail mechanism on the database connection and customizing the PostgreSQL service health checks.

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Phase 1: Fork Lab 5 Repository

Fork the previous lab repository. Your source code should include:

1. Frontend custom-built image
2. API custom-built image
3. Nginx Proxy Manager
4. MinIO
5. PostgreSQL

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Phase 2: Automate Build on Push

Create a GitHub Workflow (.github/workflows/ci.yml) that automatically builds your frontend and api images on every push to the main branch.

Because developers use different computers (e.g., Apple Silicon M-chips vs. Intel/AMD), you must build images for both linux/amd64 and linux/arm64 architectures.

Tips:

1. Use actions/checkout@v4 to checkout the repository code to the runner.
2. Use docker/login-action@v3 to log into GHCR.
3. Use docker/setup-qemu-action@v3 to prepare for multiple architecture builds.
4. Use docker/setup-buildx-action@v3 to set up the advanced builder.
5. Use docker/build-push-action@v5 to build and push each image (set platforms: linux/amd64,linux/arm64).

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Phase 3: GHCR Authentication & Visibility

To allow GitHub Actions to push images to your account, you must provide the right permissions.

1. Generate a GitHub Personal Access Token (Classic) with the write:packages scope.
2. Add this token as a Repository Secret (e.g., GHCR_PAT) and use it in your docker/login-action step.
3. Important: Once your pipeline successfully pushes the images, go to your GitHub Profile -> Packages, and change the visibility of both your newly built packages from Private to Public.

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Phase 4: Pull Images from GHCR

Now that your images are built in the cloud, update your local docker-compose.yml to pull the images directly from the GitHub Container Registry, instead of building them locally.

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Phase 5: Services' Resilience

The API may still struggle to connect to the database depending on the boot sequence. To mitigate this issue, we must fix both the API and Database services.

On the API side:

1. Add a database connection retry mechanism in your Node.js code.
2. After 5 failed retries, stop the container completely by triggering an error return code (process.exit(1)).

On the Database side:

1. Edit docker-compose.yml so the database service has a health check that confirms PostgreSQL is actually ready to accept connections.

    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}"]
      interval: 5s
      timeout: 5s
      retries: 5

2. Update the API: Modify the API's depends_on block in docker-compose.yml to wait for the database's new health condition:

    depends_on:
      postgres-db:
        condition: service_healthy