Black Mushroom

A very simple BlackJack game built with Nameko microservices framework.

Design considerations

• Enable code reuse where possible (Deck is generic, Player is generic, Game is project specific).
• Enable horizontal scaling by keeping services loosely coupled, seperate databases too.
• This is a tech demo so it was smashed out quickly, this is not an excuse but there be dragons.
• Service must operate over RPC.
• Make it easy to switch database engine.
• Use migrations to avoid having to manually mess with a database (what year is it?)
• Test coverage is unacceptable, this is not a real world project.
• I ran out of time to implement the various Docker containers but these would have been:
  1. Postgres container for each service.
  2. Application container for each service.
  3. RabbitMQ container.
  4. Some sort of load balancer such as Traefik
• I would have also liked to explore adding an HTTP / WebSocket API.
• If this was a real project I would have built a proper frontend for it (probably with React.JS)

Requirements

Core requirements

• SQLAlchemy - 1.1.9
• SQLAlchemy-Utils - 0.32.14
• Nameko - 2.5.4
• Nameko-SQLAlchemy - 0.1.0
• Marshmallow - 2.13.5
• Marshmallow-SQLAlchemy - 0.13.1
• Alembic - 0.9.1

Database driver

You will need a database driver, the default is psycopg2 but you could use sqlite or whatever.

• Psycopg2 - 2.7.1

Test requirements

• py.test - 3.0.7

Install

Install requirements

You can install the wrapper package:

pip install .

You must then also install the services

pip install src/services/base
pip install src/services/decks
pip install src/services/games
pip install src/services/players

Database migrations

To create / update the database schema run the following command:

python black_mushroom/migrate.py

Running

Run all services

nameko run black_mushroom.app --config black_mushroom/config.yml

Running individual services

Run one or more of the following commands:

nameko run black_mushroom.players.services --config config.yml
nameko run black_mushroom.decks.services --config config.yml
nameko run black_mushroom.games.services --config config.yml

Usage

You can interact with this application by using the Nameko shell, run the following:

nameko shell --config config.yml

This gives you a prompt back which you can use to call services for example to start a game:

n.rpc.game.create(n.rpc.player.create('Chris'))

After running the above command you should get a game_id returned, you can interact with the game like so:

n.rpc.game.hit(YOUR_GAME_ID_HERE)

or alternatively you could choose to stick

n.rpc.game.stick(YOUR_GAME_ID_HERE)

Which should return you a JSON representation of the game state.

Testing

You can install the test requirements by running:

pip install -r requirements.txt

When running tests you can pass database test url with --test-db-url parameter or override db_url fixture.

With in-memory SQLite database

py.test black_mushroom/tests.py

With seperate test database

py.test src/black_mushroom/tests.py --test-db-url=sqlite:///test_db.sql

Docker

Each service can be run in an independent Docker container, all dependencies (e.g. PostgreSQL, RabbitMQ etc) can be run as Docker containers. This is all handled by a docker-compose file.

If you would like to start all services under Docker please run the following command:

docker-compose run --rm wait_for_rabbit && docker-compose up