Workforce Management System

Node.js/Express backend for managing departments, employees, and leave requests with MySQL (via Sequelize) and RabbitMQ for asynchronous leave processing.

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Key Features

1. Department Management – CRUD, pagination, employee roster views, and uniqueness validation.
2. Employee Management – Lifecycle operations, department filtering, search, and leave-history retrieval.
3. Leave Management – Creation with overlap checks, idempotency keys, status updates, cancellations, and statistics.
4. Asynchronous Processing – RabbitMQ queue auto-approves short leave requests and emits follow-up events.
5. Hardening & Tooling – Helmet, CORS, rate limiting, structured logging, centralized validation, and graceful shutdowns.

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Architecture Overview

src/
├── app.js                # Express instance, middleware, routing, health endpoint
├── config/               # Database (Sequelize) & RabbitMQ configuration
├── controllers/          # HTTP handlers (Departments, Employees, LeaveRequests)
├── middleware/           # Validation, error handling, rate limiting
├── models/               # Sequelize models & associations
├── repositories/         # Data access abstractions
├── routes/               # Express routers per domain
├── services/             # Business logic & orchestration
└── queues/               # RabbitMQ consumers / processors

The app follows a layered pattern (Controller → Service → Repository → Model) to keep transport, business logic, and persistence concerns decoupled.

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Tech Stack

Concern	Technology
Runtime	Node.js (>=18)
Web Framework	Express 5
Database	MySQL + Sequelize ORM
Messaging	RabbitMQ via amqplib
Validation	express-validator, Joi (TODO)
Security	Helmet, CORS, custom rate limiting
Logging	Custom JSON logger (console)
Testing	Jest + Supertest (skeleton only)

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Getting Started

1. Prerequisites

• Node.js ≥ 18.x
• pnpm / npm / yarn (repo uses npm scripts)
• MySQL 8.x (or compatible)
• RabbitMQ (optional but recommended for async features)

2. Install Dependencies

npm install

3. Environment Variables

Create .env in the project root:

# Database
DB_HOST=localhost
DB_PORT=3306
DB_NAME=workforce_management
DB_USER=root
DB_PASSWORD=your_password

# RabbitMQ
RABBITMQ_URL=amqp://guest:guest@localhost:5672
RABBITMQ_EXCHANGE_NAME=workforce.exchange
RABBITMQ_QUEUE_NAME=workforce.leave
RABBITMQ_MAX_RETRIES=3
RABBITMQ_RETRY_DELAY=5000

# Server
PORT=3000
NODE_ENV=development

# Rate limiting (Optional overrides)
RATE_LIMIT_WINDOW_MS=900000
RATE_LIMIT_MAX_REQUESTS=100

The RabbitMQ variables are optional but required for the leave auto-processing worker. Without them the consumer logs a warning and skips startup.

4. Database Setup

The current bootstrap (server.js) runs sequelize.sync({ alter: true }) to auto-create tables. For production, replace with migrations.

5. Start the Server

npm run dev   # or npm start

The server:

• Verifies DB connectivity.
• Syncs models.
• Starts Express (defaults to http://localhost:3000).
• Boots the RabbitMQ consumer (if configured).

6. Health Check

GET /health → { status: "ok", timestamp: ... }

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API Overview

All endpoints are namespaced under /api.

Domain	Endpoints (examples)
Departments	POST /departments, GET /departments, GET /departments/:id, GET /departments/:id/employees, PUT /departments/:id, DELETE /departments/:id
Employees	POST /employees, GET /employees, GET /employees/:id, PUT /employees/:id, DELETE /employees/:id, GET /employees/:id/leave-requests
Leave Requests	POST /leave-requests, GET /leave-requests, GET /leave-requests/:id, PATCH /leave-requests/:id/status, DELETE /leave-requests/:id, GET /leave-requests/stats/:employeeId

All controllers return JSON in { success, data, pagination?, message? } shape or { success: false, error } for failures. Validation is centralized via src/middleware/validation.js.

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Asynchronous Leave Processing

1. LeaveRequestService.createLeaveRequest publishes leave.requested events.
2. src/queues/leaveRequestProcessor.js consumes the queue and:
   • Calculates leave duration.
   • Auto-approves requests shorter than AUTO_APPROVE_DAYS_THRESHOLD (defaults to 2).
   • Moves longer requests to PENDING_APPROVAL.
   • Emits leave.approved events when auto-approved.

Missing RabbitMQ credentials simply disable the consumer (with warning logs) so the API can still run synchronously.

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Scripts

Command	Description
npm run dev	Sync DB and start server (same as start)
npm test	Placeholder for Jest test suite

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Troubleshooting

Issue	Cause / Fix
SequelizeConnectionError on start	Verify DB credentials / server accessibility.
RabbitMQ consumer fails to start	Ensure RABBITMQ_URL, exchange, and queue env vars are set.
Requests rejected with 429	Rate-limiter thresholds reached; adjust env overrides for testing.
Validation errors	Check controller-specific validation rules in src/middleware/validation.js.