NestJS tip: how to run operations when the HTTP server is ready

Let's say you want to perform few tasks right after your HTTP server is ready to handle connections. Starting from @nestjs/core v10.4.8, you can now do this in a idiomatic way like the following:

// app.module.ts
import { Module } from '@nestjs/common';
import { HttpAdapterHost } from '@nestjs/core';

@Module({})
export class AppModule {
  constructor(readonly httpAdapterHost: HttpAdapterHost) {
    httpAdapterHost.listen$.subscribe({
      complete: () => this.onHttpServerListening(),
    });
  }

  async onHttpServerListening(): Promise<void> {
    console.info('HTTP server is listening');
  }
}

That console.info statement will be called after app.listen() succeeds. If the onHttpServerListening throw any error, the application will crash due to that!

You can read more about this feature here: https://docs.nestjs.com/faq/http-adapter#listening-event

Comments

[Bobby Orphé HOUESSINON]

Thanks for the tip.