DBOS + Nest.js

This guide shows you how to add DBOS durable workflows to your existing Nest.js application to make it resilient to any failure.

info

This example was bootstrapped with nest new.

You can see its full code on GitHub.

Installation and Requirements

Install the open-source DBOS TypeScript library with:

npm install @dbos-inc/dbos-sdk

Bootstrapping DBOS

First, modify your bootstrap function to configure and launch DBOS:

src/main.ts

import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';
import { DBOS } from "@dbos-inc/dbos-sdk";

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  DBOS.setConfig({
    name: 'dbos-nestjs-starter',
    systemDatabaseUrl: process.env.DBOS_SYSTEM_DATABASE_URL,
  });
  await DBOS.launch();
  await app.listen(process.env.PORT ?? 3000);
}
void bootstrap();

Add Workflows to Services

Next, you can integrate DBOS workflows into your Nest.js services by annotating or registering service methods. To register a service instance method as a workflow, its class must extend ConfiguredInstance. By extending ConfiguredInstance, you add your workflow methods to a DBOS internal registry so that if DBOS needs to recover your workflows, it can do so using the appropriate instance of your service.

Here is an example of a Nest.js service implementing a simple two-step workflow:

src/app.service.ts

import { ConfiguredInstance, DBOS } from '@dbos-inc/dbos-sdk';
import { Injectable } from '@nestjs/common';

@Injectable()
export class AppService extends ConfiguredInstance {
  constructor(name: string) {
    super(name);
  }

  async stepOne() {
    console.log('Step one completed!');
    return Promise.resolve();
  }

  async stepTwo() {
    console.log('Step two completed!');
    return Promise.resolve();
  }

  @DBOS.workflow()
  async workflow() {
    await DBOS.runStep(() => this.stepOne(), { name: 'stepOne' });
    await DBOS.runStep(() => this.stepTwo(), { name: 'stepTwo' });
    return 'Hello World!';
  }
}

Configure Service Instantiation

You can instantiate classes containing DBOS workflows during dependency injection just like any other Nest.js class. If you create multiple instances of a class containing DBOS workflows, you should give them distinct names (dbos-service-instance in this case).

src/app.modules.ts

import { Module, Provider } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';

export const appProvider: Provider = {
  provide: AppService,
  useFactory: () => {
    const service = new AppService('dbos-service-instance');
    return service;
  },
};

@Module({
  imports: [],
  controllers: [AppController],
  providers: [appProvider],
})
export class AppModule {}