Backend Folder Structure and Microservice Architecture

Overview

This project follows a microservices-based architecture, where each feature is separated into a distinct service, with individual Node.js servers and databases for each service.

Project Initialization

To initiate a new service, follow these steps:

1. Create a New Folder: Create a new folder with the desired service name.
2. Initialize NPM Project: Run npm init to initialize a new npm project.
3. Install Dependencies:
   • express: A framework for creating an Express server.
   • body-parser: Middleware for parsing incoming request bodies.
   • nodemon: A tool for automatically restarting the server during development.

Project structure includes separate src and tests folders:

• src/: Contains the main application logic and files for deployment.

  • index.js: Entry point for the application.
  • models/: Stores data models.
  • migrations/: Manages database schema changes.
  • controllers/: Handles request-response logic.
  • middlewares/: Contains middleware functions.
  • utils/: Houses utility functions.
  • config/: Holds configuration files.
  • services/: Implements business logic.
  • repository/: Manages data access logic.
  • seeders/: Populates the database with initial data.
  • routes/: Defines API routes.

• tests/: Contains test files.

• package.json: Project configuration file.

• package-lock.json: Records the exact version of each installed package.

• .gitignore: Specifies files and directories to be ignored by version control.

Setting Up Basic Express Server

1. Set Up Express Server: Establish a basic Express server.
2. Install dotenv: Use npm i dotenv to install dotenv, a zero-dependency module for loading environment variables.
3. Create .env File: Create a .env file in the root folder to store environment variables. Ensure that it is added to the .gitignore file.
4. Configure dotenv: Set up dotenv in the config folder by creating a serverConfig.js file. Refer to the documentation for further setup.

Setting Up Sequelize (ORM for MySQL)

1. Install Sequelize and MySQL Dependencies: Run npm i mysql2 sequelize sequelize-cli to install Sequelize and MySQL dependencies.
2. Initialize Sequelize: Run npx sequelize init to generate the necessary folders (config, migrations, models, seeders).
3. Configure Sequelize: Edit config/config.json with local MySQL server details and create a database using npx sequelize db:create in the src folder.

Creating Models

1. Generate Model: In the src folder, run npx sequelize model:generate --name <Model Name> --attributes <Schemas>:<type> to generate a model.
2. Run Migrations: Execute npx sequelize db:migrate to run migrations and create a table in the local database.
3. Undo Migrations: Use npx sequelize db:migrate:undo to undo migrated files.

Repository and Service Layers

1. Repository Layer: In the repository folder, create a <Model Name> repository file for CRUD operations.
2. Export Repositories: Create an index.js file in the repository folder to export all repositories as a single object.
3. Service Layer: Repeat the same structure for the services folder.

Database Structure

1. Create Model: Begin by creating a model.
2. Repository Layer: Create a file in the repository folder for CRUD API operations. The repository layer communicates with any layer or the database.
3. Service Layer: In the services layer, create a file for the model. The service layer is responsible for business logic and calls the repository layer. Create CRUD functions similar to the repository layer.
4. Controllers: Controllers call services. Controllers are functions; create named functions (e.g., const create = (req, res) => {}).
5. Express Router: Use Express Router. Create an index.js file for routing. Combine files using export/import. In folder files, use controller functions (e.g., router.use("/name", controllerFunc)).
6. Main API Routes: In the main index.js file, write the main API routes (e.g., app.use("/api", routesFunc)).
7. Seeders: Seeders are used to add hardcoded data into the database.

PostgreSQL Commands

For working with PostgreSQL, here are some useful commands:

sudo -i -u postgres        # Open PostgreSQL server terminal
psql                       # Open PostgreSQL database terminal
sudo systemctl status postgresql.service  # Show PostgreSQL server status
sudo systemctl start postgresql.service   # Start PostgreSQL server locally
sudo systemctl stop postgresql.service    # Stop PostgreSQL server locally
\l                          # List all databases
\c database_name            # Switch to a database or use a database
\dt                         # Show all available tables
\d table_name               # Describe table
\x                          # Expanded display (recommended to turn off)
TABLE "table_name";         # View table data