How to raise an HTTP exception from a subsequent command that failed in a saga in NestJS CQRS?

Question

I'm using NestJS CQRS recipe in order to manage interactions between two entities: User and UserProfile. The architecture is an API Gateway NestJS server + a NestJS server for each microservice (User, UserProfile, etc.).

I have already set up basic interactions through User and UserProfile modules on API Gateway with their own sagas/events/commands:

When a user is created, a user profile is created
When the user profile creation fails, the previously created user is deleted

In details:

In User module, CreateUser command raises a UserCreated event that is intercepted by User saga, which will trigger CreateUserProfile command (from UserProfile module).

If the latter fails, a UserProfileFailedToCreate event is raised and intercepted by UserProfile saga, which will trigger DeleteUser command (from User module).

Everything works fine.

If the CreateUser command fails, I resolve(Promise.reject(new HttpException(error, error.status)) which indicates to the end user that something went wrong during the user creation.

My problem is that I cannot replicate the same behavior for the CreateUserProfile command since the HTTP request promise has already been resolved from the first command, obviously.

So my question is: is there any way to make a command fail if a subsequent command fails in the saga? I understand that the HTTP request is totally disconnected from any subsequent commands triggered by a saga, but I want to know if anybody has already played with events or something else here to replicate this data flow?

One of the reasons I'm using CQRS, besides having a much cleaner code for data interactions among microservices, is to be able to rollback repositories actions in case any of the chained commands fails, which works fine. But I need a way to indicate to the end user that the chain went through an issue and was rollbacked.

UserController.ts

@Post('createUser')
async createUser(@Body() createUserDto: CreateUserDto): Promise<{user: IAuthUser, token: string}> {
  const { authUser } = await this.authService.createAuthUser(createUserDto);
  // this is executed after resolve() in CreateUserCommand
  return {user: authUser, token: this.authService.createAccessTokenFromUser(authUser)};
}

UserService.ts

async createAuthUser(createUserDto: CreateUserDto): Promise<{authUser: IAuthUser}> {
  return await this.commandBus
    .execute(new CreateAuthUserCommand(createUserDto))
    .catch(error => { throw new HttpException(error, error.status); });
}

CreateUserCommand.ts

async execute(command: CreateAuthUserCommand, resolve: (value?) => void) {
    const { createUserDto } = command;
    const createAuthUserDto: CreateAuthUserDto = {
      email: createUserDto.email,
      password: createUserDto.password,
      phoneNumber: createUserDto.phoneNumber,
    };

    try {
      const user = this.publisher.mergeObjectContext(
        await this.client
          .send({ cmd: 'createAuthUser' }, createAuthUserDto)
          .toPromise()
          .then((dbUser: IAuthUser) => {
            const {password, passwordConfirm, ...publicUser} = Object.assign(dbUser, createUserDto);
            return new AuthUser(publicUser);
          }),
      );
      user.notifyCreated();
      user.commit();
      resolve(user); // <== This makes the HTTP request return its reponse
    } catch (error) {
      resolve(Promise.reject(error));
    }
  }

UserSagas.ts

authUserCreated = (event$: EventObservable): Observable => {
    return event$
      .ofType(AuthUserCreatedEvent)
      .pipe(
        map(event => {
          const createUserProfileDto: CreateUserProfileDto = {
            avatarUrl: '',
            firstName: event.authUser.firstName,
            lastName: event.authUser.lastName,
            nationality: '',
            userId: event.authUser.id,
            username: event.authUser.username,
          };
          return new CreateUserProfileCommand(createUserProfileDto);
        }),
      );
  }

CreateUserProfileCommand.ts

async execute(command: CreateUserProfileCommand, resolve: (value?) => void) {
    const { createUserProfileDto } = command;

    try {
      const userProfile = this.publisher.mergeObjectContext(
        await this.client
          .send({ cmd: 'createUserProfile' }, createUserProfileDto)
          .toPromise()
          .then((dbUserProfile: IUserProfile) => new UserProfile(dbUserProfile)),
      );
      userProfile.notifyCreated();
      userProfile.commit();
      resolve(userProfile);
    } catch (error) {
      const userProfile = this.publisher.mergeObjectContext(new UserProfile({id: createUserProfileDto.userId} as IUserProfile));
      userProfile.notifyFailedToCreate();
      userProfile.commit();
      resolve(Promise.reject(new HttpException(error, 500)).catch(() => {}));
    }
  }

UserProfileSagas.ts

userProfileFailedToCreate = (event$: EventObservable): Observable => {
    return event$
      .ofType(UserProfileFailedToCreateEvent)
      .pipe(
        map(event => {
          return new DeleteAuthUserCommand(event.userProfile);
        }),
      );
  }

DeleteUserCommand.ts

async execute(command: DeleteAuthUserCommand, resolve: (value?) => void) {
    const { deleteAuthUserDto } = command;

    try {
      const user = this.publisher.mergeObjectContext(
        await this.client
          .send({ cmd: 'deleteAuthUser' }, deleteAuthUserDto)
          .toPromise()
          .then(() => new AuthUser({} as IAuthUser)),
      );
      user.notifyDeleted();
      user.commit();
      resolve(user);
    } catch (error) {
      resolve(Promise.reject(new HttpException(error, error.status)).catch(() => {}));
    }
  }

How to raise an HTTP exception from a subsequent command that failed in a saga in NestJS CQRS?

Answers (1)

Related Questions