This project is a distributed notification system built using a microservices architecture.
It consists of independent services communicating via RabbitMQ, with PostgreSQL as each service’s database, Redis for caching, and Swagger/OpenAPI for documentation.

/notification-system
├── docker-compose.yml
├── README.md
├── .env
│
├── gateway/                # NestJS - Entry point (API Gateway)
│   ├── src/
│   ├── package.json
│   └── Dockerfile
│
├── user-service/           # NestJS - Handles users
│   ├── src/
│   ├── package.json
│   └── Dockerfile
│
├── template-service/       # Flask - Handles message templates
│   ├── app/
│   ├── requirements.txt
│   └── Dockerfile
│
├── worker-service/         # Spring Boot - Background tasks / delivery
│   ├── src/
│   ├── pom.xml
│   └── Dockerfile
│
└── infra/
    ├── postgres/           # Volume configs for Postgres DBs
    ├── redis/
    └── rabbitmq/

• Docker
• Docker Compose
• Git

Clone the repository:

git clone https://github.com/<your-org>/notification-system.git
cd notification-system

Create a .env file in the root directory with the following variables:

# Shared
RABBITMQ_USER=admin
RABBITMQ_PASS=admin
REDIS_PORT=6379

# Gateway Service
GATEWAY_DB_USER=gateway_user
GATEWAY_DB_PASS=gateway_pass
GATEWAY_DB_NAME=gateway_db

# User Service
USER_DB_USER=user_user
USER_DB_PASS=user_pass
USER_DB_NAME=user_db

# Template Service
TEMPLATE_DB_USER=template_user
TEMPLATE_DB_PASS=template_pass
TEMPLATE_DB_NAME=template_db

# Worker Service
STATUS_DB_HOST=postgres_worker
STATUS_DB_NAME=worker_db

Each service connects to its own DB using the variables above.

DATABASE_URL=postgresql://${GATEWAY_DB_USER}:${GATEWAY_DB_PASS}@postgres_gateway:5432/${GATEWAY_DB_NAME}
RABBITMQ_URL=amqp://${RABBITMQ_USER}:${RABBITMQ_PASS}@rabbitmq:5672/
REDIS_URL=redis://redis:6379

DATABASE_URL=postgresql://${USER_DB_USER}:${USER_DB_PASS}@postgres_user:5432/${USER_DB_NAME}

SQLALCHEMY_DATABASE_URI=postgresql://${TEMPLATE_DB_USER}:${TEMPLATE_DB_PASS}@postgres_template:5432/${TEMPLATE_DB_NAME}

SPRING_DATASOURCE_URL=jdbc:postgresql://${STATUS_DB_HOST}:5432/${STATUS_DB_NAME}
SPRING_RABBITMQ_HOST=rabbitmq

All services are orchestrated through Docker Compose.

To start everything:

docker compose up --build

To stop all containers:

docker compose down

Each developer should:

1. Clone the repo
2. Create a .env file as shown above
3. Ensure Docker is running
4. Run the system using:

   docker compose up --build

5. Verify their service starts up correctly

If you modify any service dependencies:

Rebuild only that service:

docker compose build <service_name>

Example:

docker compose build gateway

To see logs of a specific service:

docker compose logs -f gateway

• Add Swagger documentation for each service
• Set up message queues for communication
• Add proper error handling and retry mechanisms
• Create a shared proto or schema folder for message contracts