backend-setup

Backend Setup

When to Use

• Starting backend development
• Adding Express middleware
• Troubleshooting server startup
• Designing plugin architecture
• Initializing new activity modules

What This Skill Does

Scaffolds Express server with CampusOS plugin system, middleware templates, modular structure, and service initialization patterns.

Procedure

Phase 1: Project Structure

1. Start in /backend/src/
2. Create directory structure:

   src/
   ├── index.js
   ├── app.js
   ├── server.js
   ├── plugin-loader.js
   ├── middleware/
   │   ├── auth.js
   │   ├── error.js
   │   └── logger.js
   └── utils/
       └── registry.js
   

Phase 2: Core Components

1. Create index.js - Express app initialization with express()
2. Create app.js - Load middleware in correct order (auth → routes → error handling)
3. Create server.js - HTTP server startup on configured PORT
4. Create plugin-loader.js - Dynamic module discovery from /apps/

Phase 3: Middleware Implementation

1. Authentication middleware - Verify JWT/tokens before route handlers
2. Error handling middleware - Catch and format errors at end of chain
3. Logging middleware - Track all requests/responses
4. CORS configuration - Handle cross-origin requests

Phase 4: Plugin System

1. Initialize module registry in utils/registry.js
2. Scan /apps/ directory for modules with index.js
3. Call module.init(app, registry) for each module
4. Register routes via app.post(), app.get() from each module
5. Mount services/authenticators/resolvers

Quick Reference

cd backend && pnpm install
npm run dev        # Start dev server with hot reload
npm run build      # Compile TypeScript (if used)
npm test          # Run integration tests
# Set custom port: PORT=3001 npm run dev

Common Issues

Issue	Solution
Plugin not loading	Check /apps/module/src/index.js exports init() function
Middleware order wrong	Place auth before routes, error handler at end of chain
Port in use	Change PORT env var or kill process: lsof -i :3000
Routes undefined	Verify module calls app.post() during init phase
CORS errors	Configure CORS middleware with allowed origins
Services not registered	Ensure registry.set() called during module initialization