Connectinno Case Study

Technologies Used

• Python 3.11
• Docker
• FastAPI
• Firebase Storage (GCS)
• SQLAlchemy

Getting started

Development Environment

1. Install poetry curl -sSL https://install.python-poetry.org | python3 -
2. Install uv package manager curl -LsSf https://astral.sh/uv/install.sh | sh
3. RUN poetry install --only-root to create a new poetry environment
4. RUN uv pip install -r pyproject.toml
5. Install pre-commit and ruff linter uv pip install pre-commit ruff
6. RUN pre-commit install
7. RUN pre-commit run

Running inside Docker Engine

Install Docker Engine

sudo apt-get update
sudo apt-get install \
    ca-certificates \
    curl \
    gnupg \
    lsb-release
sudo mkdir -p /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-compose-plugin

Verify that Docker Engine is installed correctly by running the hello-world image.

sudo docker run hello-world

Compile Images

After you have installed docker-engine and docker-compose,

cp .env.example .env
sudo docker compose build

Note: make sure to tweak .env file according to your preferences

Running Services

After you have compiled the images successfully do the following:

1. Add service account JSON file to resources folder and make sure to exclude the file from git, you just have to include firebase-adminsdk in file name.
2. Update GOOGLE_APPLICATION_CREDENTIALS environment variable and point it to service account JSON filepath.
3. Run the following commands

   sudo docker compose up -d
   sudo docker compose exec web alembic upgrade head

Now you can access the API documentation in your browser.

Common errors

• An error related to *.sh script not found
  1. Change line endings for the related script in docker directory to LF(Unix)
  2. Rebuild the image

Running Tests

sudo docker compose up -d
sudo docker compose exec web pytest

System Design

• Repository pattern: A simplifying abstraction over data storage that hide the complexity of DB operations from the client.
• UoW pattern: It’s a nice place to put all your repositories so client code can access them. It helps to enforce the consistency of our domain model, and improves performance, by letting us perform a single flush operation at the end of an operation
• Inverting the Dependency: ORM Depends on Model not the other way around i.e. high-level modules (the domain) should not depend on low-level ones (the infrastructure)
• Dependency Injection: It adds flexibility as the components are loosely coupled and can be easily swapped with mocks or fakes. Also, enhances code maintainability by clearly defining where dependencies are used and making it easier to identify and update them when needed.
• Factory pattern: Use factory method to abstract filesystems behaviour and let the client rely on a single interface AbstractFileSystem. Hence, we can easily migrate to s3 or local simply by changing the injected factory