shancheas
0b0bdd9c4b
- Introduced backend patterns skill with guidelines on API design, database optimization, and server-side best practices. - Added coding standards skill outlining universal coding principles for TypeScript, NestJS, and Node.js development. - Implemented continuous learning skill to automatically extract reusable patterns from Cursor sessions. - Created NestJS best practices skill detailing architecture patterns, dependency injection, error handling, and security measures. - Included various rules and templates for NestJS best practices to ensure production-ready applications.
3.0 KiB
3.0 KiB
title, impact, impactDescription, tags
| title | impact | impactDescription | tags |
|---|---|---|---|
| Use Event-Driven Architecture for Decoupling | MEDIUM-HIGH | Enables async processing and modularity | architecture, events, decoupling |
Use Event-Driven Architecture for Decoupling
Use @nestjs/event-emitter for intra-service events and message brokers for inter-service communication. Events allow modules to react to changes without direct dependencies, improving modularity and enabling async processing.
Incorrect (direct service coupling):
// Direct service coupling
@Injectable()
export class OrdersService {
constructor(
private inventoryService: InventoryService,
private emailService: EmailService,
private analyticsService: AnalyticsService,
private notificationService: NotificationService,
private loyaltyService: LoyaltyService,
) {}
async createOrder(dto: CreateOrderDto): Promise<Order> {
const order = await this.repo.save(dto);
// Tight coupling - OrdersService knows about all consumers
await this.inventoryService.reserve(order.items);
await this.emailService.sendConfirmation(order);
await this.analyticsService.track('order_created', order);
await this.notificationService.push(order.userId, 'Order placed');
await this.loyaltyService.addPoints(order.userId, order.total);
// Adding new behavior requires modifying this service
return order;
}
}
Correct (event-driven decoupling):
// Use EventEmitter for decoupling
import { EventEmitter2 } from '@nestjs/event-emitter';
// Define event
export class OrderCreatedEvent {
constructor(
public readonly orderId: string,
public readonly userId: string,
public readonly items: OrderItem[],
public readonly total: number,
) {}
}
// Service emits events
@Injectable()
export class OrdersService {
constructor(
private eventEmitter: EventEmitter2,
private repo: Repository<Order>,
) {}
async createOrder(dto: CreateOrderDto): Promise<Order> {
const order = await this.repo.save(dto);
// Emit event - no knowledge of consumers
this.eventEmitter.emit(
'order.created',
new OrderCreatedEvent(order.id, order.userId, order.items, order.total),
);
return order;
}
}
// Listeners in separate modules
@Injectable()
export class InventoryListener {
@OnEvent('order.created')
async handleOrderCreated(event: OrderCreatedEvent): Promise<void> {
await this.inventoryService.reserve(event.items);
}
}
@Injectable()
export class EmailListener {
@OnEvent('order.created')
async handleOrderCreated(event: OrderCreatedEvent): Promise<void> {
await this.emailService.sendConfirmation(event.orderId);
}
}
@Injectable()
export class AnalyticsListener {
@OnEvent('order.created')
async handleOrderCreated(event: OrderCreatedEvent): Promise<void> {
await this.analyticsService.track('order_created', {
orderId: event.orderId,
total: event.total,
});
}
}
Reference: NestJS Events