Nest could not find Sequelize element when calling `app.close()`

Question

We have a web server running Nest 8.0.8. With the given module setup:

@Module({
  imports: [
    ConfigModule.forRoot({
      isGlobal: true,
      cache: true,
      validate,
      load: [configuration]
    }),
    SequelizeModule.forRootAsync({
      imports: [ConfigModule],
      useFactory: (config: ConfigService) => config.get('db1'),
      inject: [ConfigService]
    }),
    SequelizeModule.forRootAsync({
      name: 'db2',
      imports: [ConfigModule],
      useFactory: (config: ConfigService) => config.get('db2'),
      inject: [ConfigService],
    }),
  controllers: [...],
  providers: [...]
})

To start the application, we have this main.ts file:

async function bootstrap() {

  const app = await NestFactory.create<NestFastifyApplication>(
    AppModule,
    new FastifyAdapter(...)
  );

  useContainer(app.select(AppModule), { fallbackOnErrors: true });

  app.useGlobalPipes(
    new ValidationPipe({
      exceptionFactory: (errors) => new ValidationException(errors),
      transform: true,
      whitelist: true,
      validationError: {
        target: false,
        value: false
      }
    })
  );

  app.setGlobalPrefix('v1');

  app.useWebSocketAdapter(new RedisIoAdapter(app));

  app.enableCors({ origin: '*' });

  /**
   * When SIGTERM, run functions before shutting down
   */
  app.enableShutdownHooks();

  if (process.env.SETUP) {
    const service = app.get(FooService);
    await service.setup();
    await app.close();
    return;
  }

  await app.listen(3000, '0.0.0.0');
}

bootstrap().then();

When running out unit tests, we use Nest to automatically configure the database. Initially after initializing the server with the command SETUP=true nest start that will force Nest to not listen the port and early return after running service.setup(). (note that this problem also happens when calling the app.listen(...) and app.close() functions)

The problem happens at the call app.close() we expect Nest to close all connections, including the two SequelizeModule of the 2 databases connected.

Unfortunaly Nest closes the first connection and tries to close the second, but the module (we suspect) is already closed. Giving the error:

This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason:
Error: Nest could not find Sequelize element (this provider does not exist in the current context)
    at InstanceLinksHost.get (/Users/me/Repository/project_nest/node_modules/@nestjs/core/injector/instance-links-host.js:21:19)
    at Object.find (/Users/me/Repository/project_nest/node_modules/@nestjs/core/injector/module-ref.js:38:55)
    at Object.get (/Users/me/Repository/project_nest/node_modules/@nestjs/core/injector/module.js:345:28)
    at SequelizeCoreModule.<anonymous> (/Users/me/Repository/project_nest/node_modules/@nestjs/sequelize/dist/sequelize-core.module.js:81:47)
    at Generator.next (<anonymous>)
    at /Users/me/Repository/project_nest/node_modules/@nestjs/sequelize/dist/sequelize-core.module.js:20:71
    at new Promise (<anonymous>)
    at __awaiter (/Users/me/Repository/project_nest/node_modules/@nestjs/sequelize/dist/sequelize-core.module.js:16:12)
    at SequelizeCoreModule.onApplicationShutdown (/Users/me/Repository/project_nest/node_modules/@nestjs/sequelize/dist/sequelize-core.module.js:80:16)
    at Object.callAppShutdownHook (/Users/me/Repository/project_nest/node_modules/@nestjs/core/hooks/on-app-shutdown.hook.js:51:35)
    at processTicksAndRejections (node:internal/process/task_queues:96:5)
    at NestApplication.callShutdownHook (/Users/me/Repository/project_nest/node_modules/@nestjs/core/nest-application-context.js:199:13)
    at NestApplication.close (/Users/me/Repository/project_nest/node_modules/@nestjs/core/nest-application-context.js:83:9)
    at bootstrap (/Users/me/Repository/project_nest/src/main.ts:143:5)

We initially thing that is a problem on Nest but we are not sure. This used to work in the past but somehow after a update the issue started happening and we cannot downgrade the library due some constraints with other dependencies.

I would like to know what can be done to either debug or sort the issue, we tried to debug the application but nothing points out to issues in our codebase. Could you please help?

Regards, Pedro

Answer 1

you need to give name for you second configuration SequelizeModule. Example for your situation

SequelizeModule.forRootAsync({
  name: 'db2',
  imports: [ConfigModule],
  useFactory: (config: ConfigService) => {
    name: 'db2',
    ...config.get('db2')
  },
  inject: [ConfigService],
}),

The reason of this problem is getConnectionToken function which uses for getting connection by name from options. And if you not use specific name, SequelizeModule will use one connection between two modules and will close them both