microservices

• 传输
  • TCP
  • Redis Pub/Sub
    • 不做处理会被多个 服务端 处理
    • 用 redis stream 可以避免重复消费问题
      • tamimaj/nestjs-redis-streams
      • 但会有 stale 问题，需要注意
  • MQTT Pub/Sub - {data,headers}
  • NATS reqreply, pubsub
  • RabbitMQ
  • Kafka
  • gRPC
• 核心模块不会增加额外的传输策略
  • https://github.com/nestjs/nest/issues/3960#issuecomment-771647374
• pattern
  • 会序列化为 JSON - 因此可以用 Object
• @MessagePattern({ cmd: '' }) - 请求响应
  • 支持返回 Promise, Observable
• @EventPattern('') - 事件
• ClientProxy
  • ClientsModule.register() - 注册后使用
  • @Client({ transport: Transport.TCP }) client: ClientProxy; - 直接注解使用
• adopted by
  • amplication/amplication
• 实现依赖 rxjs
• 参考
  • https://amplication.com/blog/working-with-microservices-with-nestjs

npm add rxjs @nestjs/microservices

import { NestFactory } from '@nestjs/core';
import { Transport, MicroserviceOptions } from '@nestjs/microservices';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.createMicroservice<MicroserviceOptions>(AppModule, {
    transport: Transport.TCP,
  });
  await app.listen();
}
bootstrap();

import { Controller } from '@nestjs/common';
import { MessagePattern } from '@nestjs/microservices';

@Controller()
export class MathController {
  @MessagePattern({ cmd: 'sum' })
  accumulate(data: number[]): number {
    return (data || []).reduce((a, b) => a + b);
  }
}

import { Injectable, Scope, Inject } from '@nestjs/common';
import { CONTEXT, RequestContext } from '@nestjs/microservices';

@Injectable({ scope: Scope.REQUEST })
export class CatsService {
  constructor(@Inject(CONTEXT) private ctx: RequestContext) {}
}

export interface RequestContext<T = any> {
  pattern: string | Record<string, any>;
  data: T;
}

Hybrid application

• HTTP + Microservice

const app = await NestFactory.create(AppModule);
const microservice = app.connectMicroservice<MicroserviceOptions>({
  transport: Transport.TCP,
});

await app.startAllMicroservices();
await app.listen(3001);

• https://docs.nestjs.com/faq/hybrid-application