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

Hybrid application​

Hybrid application