Взаимодействие между сервисами
Реализуйте шаблоны эффективного взаимодействия между микросервисами, включая механизмы на основе событий и запросов-ответов.
«Взаимодействие между сервисами» — бесплатный урок NestJS Enterprise Backend APIs на CoddyKit. Это урок 3 из 3. Ты можешь прочитать весь урок бесплатно ниже — а потом практиковать его прямо в браузере с встроенным редактором кода и ИИ-репетитором 24/7. Это часть пути обучения NestJS Enterprise Backend APIs, и твой прогресс синхронизируется между веб-версией и приложением CoddyKit. Курс NestJS Enterprise Backend APIs содержит 3 уроков всего.
Части этого урока еще не переведены и отображаются на английском.
Microservices Need to Talk
Microservices are designed to be independent, but they often need to collaborate to complete complex tasks. This means they must communicate with each other!
In this lesson, we'll explore the main patterns for how your NestJS microservices can send messages and share data effectively.
Sync vs. Async Communication
Understanding the difference between synchronous and asynchronous communication is crucial for microservices:
- Synchronous: The sender waits for an immediate reply. It's like a direct phone call where you expect an answer right away.
- Asynchronous: The sender doesn't wait for a reply. It's like sending an email – you send it and continue with other tasks, expecting a reply later (or not at all).
Both patterns have distinct use cases in a distributed system.
Request-Response Pattern
The Request-Response pattern is a synchronous communication method. One service (the client) sends a request to another service (the server) and pauses its own execution, waiting for a direct response.
- Ideal for operations needing an immediate result.
- Similar to how a typical web client interacts with a REST API.
- Often implemented using HTTP, RPC, or message brokers configured for synchronous replies.
NestJS: Receiving Requests
In NestJS, a microservice listens for incoming requests using the @MessagePattern() decorator. This pattern must match the one sent by the client.
The decorated handler function receives the payload and returns a response. Try running this Product Service microservice:
import { NestFactory } from '@nestjs/core';
import { MicroserviceOptions, Transport } from '@nestjs/microservices';
import { Module, Controller, MessagePattern } from '@nestjs/common';
@Controller()
class ProductController {
@MessagePattern('get_product_details')
getProductDetails(id: string): any {
console.log(`Product Service: Request for ID: ${id}`);
const products = {
'1': { id: '1', name: 'Laptop', price: 1200 },
'2': { id: '2', name: 'Mouse', price: 25 },
};
return products[id] || { id, name: 'Product Not Found', price: 0 };
}
}
@Module({
controllers: [ProductController],
})
class AppModule {}
async function bootstrap() {
const app = await NestFactory.createMicroservice<MicroserviceOptions>(
AppModule,
{
transport: Transport.TCP,
options: { host: '127.0.0.1', port: 8877 },
},
);
await app.listen();
console.log('Product Microservice is listening on port 8877');
}
bootstrap();NestJS: Sending Requests
To send a request to the 'Product Service' (from the previous scene), another microservice or an API Gateway uses a ClientProxy.
The client.send() method dispatches a message with a specific pattern and payload, returning an RxJS Observable that resolves with the response.
This snippet shows how a client service would initiate the request:
// product-client.service.ts in 'Order Service' microservice
import { Injectable, Inject } from '@nestjs/common';
import { ClientProxy } from '@nestjs/microservices';
import { lastValueFrom } from 'rxjs'; // For awaiting observable
@Injectable()
export class ProductClientService {
constructor(@Inject('PRODUCT_SERVICE') private client: ClientProxy) {}
async fetchProduct(productId: string): Promise<any> {
console.log(`Order Service: Fetching product ID: ${productId}`);
// 'get_product_details' must match the pattern in Product Service
const product = await lastValueFrom(
this.client.send('get_product_details', productId),
);
console.log('Received product:', product);
return product;
}
}
// To make this work, 'PRODUCT_SERVICE' needs to be registered
// in an AppModule using ClientsModule.register():
// imports: [
// ClientsModule.register([
// {
// name: 'PRODUCT_SERVICE',
// transport: Transport.TCP,
// options: { host: '127.0.0.1', port: 8877 },
// },
// ]),
// ],When to Use Request-Response
The Request-Response pattern is best when:
- You need an immediate answer from the target service.
- The operation is critical and requires direct feedback (e.g., payment processing, user authentication).
- You are fetching specific data from another service.
- The interaction is a clear client-server relationship.
Be aware that this pattern introduces direct coupling between services.
Event-Based Communication
Event-based communication is an asynchronous pattern that uses a 'publish-subscribe' model. Services don't directly call each other; instead, they publish events to a message broker (like RabbitMQ) when something notable happens.
- A service publishes an event (e.g., 'OrderCreated').
- Other services subscribe to events they are interested in.
- This pattern greatly decouples services, making them more independent.
NestJS: Publishing Events
To publish an event in NestJS, you use the client.emit() method of a ClientProxy. Unlike send(), emit() sends the event and immediately returns, not waiting for a response.
This 'fire-and-forget' approach is ideal for notifying other services about state changes. Run this Order Service that emits an event:
import { NestFactory } from '@nestjs/core';
import { Module, Controller, Post, Body, Inject } from '@nestjs/common';
import { ClientProxy, ClientsModule, Transport } from '@nestjs/microservices';
interface OrderCreatedEvent {
orderId: string;
userId: string;
totalAmount: number;
}
@Controller('orders')
class OrderController {
constructor(@Inject('NOTIFICATION_SERVICE') private client: ClientProxy) {}
@Post()
async createOrder(@Body() orderData: any) {
const orderId = `ORD-${Date.now()}`;
const event: OrderCreatedEvent = {
orderId,
userId: orderData.userId || 'user-123',
totalAmount: orderData.amount || 100,
};
this.client.emit('order_created', event);
console.log(`Order ${orderId} created, 'order_created' event emitted.`);
return { message: 'Order created and event sent', orderId };
}
}
@Module({
imports: [
ClientsModule.register([
{
name: 'NOTIFICATION_SERVICE',
transport: Transport.TCP,
options: { host: '127.0.0.1', port: 8878 },
},
]),
],
controllers: [OrderController],
})
class AppModule {}
async function bootstrap() {
const app = await NestFactory.create(AppModule);
await app.listen(3000);
console.log('Order Service (HTTP) is listening on port 3000');
}
bootstrap();NestJS: Listening to Events
Other microservices can subscribe to events using the @EventPattern() decorator. When an event with a matching pattern is emitted, the decorated method is automatically triggered.
This allows multiple services to react to the same event independently. Run this Notification Service to receive the event:
import { NestFactory } from '@nestjs/core';
import { MicroserviceOptions, Transport } from '@nestjs/microservices';
import { Module, Controller, EventPattern } from '@nestjs/common';
interface OrderCreatedEvent {
orderId: string;
userId: string;
totalAmount: number;
}
@Controller()
class NotificationController {
@EventPattern('order_created')
handleOrderCreated(data: OrderCreatedEvent) {
console.log('Notification Service received OrderCreated event:', data);
console.log(`Sending notification for Order ${data.orderId} to User ${data.userId}`);
}
}
@Module({
controllers: [NotificationController],
})
class AppModule {}
async function bootstrap() {
const app = await NestFactory.createMicroservice<MicroserviceOptions>(
AppModule,
{
transport: Transport.TCP,
options: { host: '127.0.0.1', port: 8878 },
},
);
await app.listen();
console.log('Notification Microservice is listening on port 8878');
}
bootstrap();When to Use Event-Driven
Event-based communication is highly beneficial for:
- Decoupling: Services don't need to know about each other, reducing dependencies.
- Broadcasting: Notifying multiple consumers about a single event (e.g., 'UserRegistered' event).
- Long-running processes: Initiating tasks that don't require an immediate response.
- Resilience: Services can process events when they are available, improving fault tolerance.
It adds complexity but offers great flexibility and scalability.
Communication Patterns Quiz
Consider a scenario where an 'Order Service' needs to inform a 'Shipping Service' that an order is ready to be shipped, but the 'Order Service' doesn't need to wait for the shipping confirmation immediately. Which communication pattern is best suited for this?
Recap: Talking Services
Congratulations! You've learned about the fundamental patterns for inter-service communication in NestJS microservices.
- Request-Response (using
client.send()and@MessagePattern()) is for immediate, direct interactions where a reply is expected. - Event-Based (using
client.emit()and@EventPattern()) is for asynchronous, decoupled communication via events, ideal for notifications and broadcasting.
Choosing the right pattern depends on your specific needs for coupling, responsiveness, and scalability in your distributed system.
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Часто задаваемые вопросы
Урок «Взаимодействие между сервисами» бесплатный?
Да — полный текст урока «Взаимодействие между сервисами» бесплатно доступен здесь в веб-версии. Чтобы практиковать его интерактивно (встроенный редактор кода и ИИ-репетитор 24/7) и разблокировать остальной курс NestJS Enterprise Backend APIs, подпишись на CoddyKit PRO. Курс NestJS Enterprise Backend APIs содержит 3 уроков всего.
Чему я научусь в уроке «Взаимодействие между сервисами»?
Реализуйте шаблоны эффективного взаимодействия между микросервисами, включая механизмы на основе событий и запросов-ответов. Ты практикуешь NestJS Enterprise Backend APIs с помощью реального кода, который запускаешь прямо в браузере, и ИИ-репетитор 24/7 отвечает на твои вопросы во время урока.
Нужен ли мне опыт, чтобы начать NestJS Enterprise Backend APIs?
Предыдущий опыт не требуется. NestJS Enterprise Backend APIs на CoddyKit структурирован для всех уровней — от новичков до продвинутых, поэтому ты можешь начать отсюда или с самого начала и учиться в своем темпе. Это урок 3 из 3.
Сколько времени занимает урок «Взаимодействие между сервисами»?
Большинство уроков CoddyKit занимают около 5–10 минут. Каждый из них компактный и интерактивный, поэтому ты постоянно делаешь прогресс и продолжаешь с того же места в веб-версии и приложении.
Можно ли писать и запускать код в этом уроке NestJS Enterprise Backend APIs?
Да. Каждый урок NestJS Enterprise Backend APIs включает встроенный редактор кода, поэтому ты пишешь и запускаешь реальный код прямо в браузере и получаешь моментальную обратную связь от AI — локальная установка не требуется.
Все уроки этого курса
- Обзор микросервисов NestJS
- Интеграция RabbitMQ
- Взаимодействие между сервисами