How to handle RpcException in NestJS

Question

I am trying to build a NestJS backend with multiple microservices and one REST API as a Gateway which communicates with the microservices. For communication between the Gateway and Microservices I am using gRPC. Simple communication is already working, but now I wanted to implement Error Handling in the Microservices. The NestJS Documentation states that this is possible with the RpcException class.https://docs.nestjs.com/microservices/exception-filters But if I try to catch the Exception in the Gateway API I only get "ERROR [ExceptionsHandler] 2 UNKNOWN: ..." followed by the Exceptions error message.

Gateway API: user.controller.ts

import { Controller, Get, Param } from '@nestjs/common';
import { ApiTags } from '@nestjs/swagger';
import { UserViewModel } from '../../proto/build/service-name/user';
import { UserService } from './user.service';

@Controller('user')
export class UserController {
  constructor(private readonly userService: UserService) {}

  @Get(':id')
  async getUserById(@Param('id') id: number): Promise {
    try {
      return await this.userService.getUserById(id);
    } catch (error) {
      return error;
    }
  }
}

Gateway API: user.service.ts

import { Inject, Injectable, OnModuleInit } from '@nestjs/common';
import { ClientGrpc } from '@nestjs/microservices';
import {
  IUserService,
  UserViewModel,
} from '../../proto/build/service-name/user';

@Injectable()
export class UserService implements OnModuleInit {
  private grpcService: IUserService;

  constructor(@Inject('USER_PACKAGE') private client: ClientGrpc) {}

  onModuleInit() {
    this.grpcService = this.client.getService('IUserService');
  }

  async getUserById(id: number): Promise {
    return this.grpcService.getUserById({ id });
  }
}

Microservice: user.controller.ts

import { Metadata } from '@grpc/grpc-js';
import { Controller } from '@nestjs/common';
import { GrpcMethod, RpcException } from '@nestjs/microservices';
import { User } from './../../node_modules/.prisma/client/index.d';
import { PrismaService } from '../prisma/prisma.service';
import { UserViewModel, GetUserById } from '../proto/build/service-name/user';

@Controller()
export class UserController {
  constructor(private readonly prisma: PrismaService) {}

  @GrpcMethod('IUserService', 'getUserById')
  async getUserById(
    data: GetUserById,
    metadata: Metadata,
  ): Promise {
    const user: User = await this.prisma.user.findFirst({
      where: { id: { equals: data.id } },
    });

    if (!user) {
      throw new RpcException('User not found');
    }

    return { name: user.name, email: user.email };
  }
}

user_11778341 · Answer

Extend the RpcException and use in the microservice.
Create AllGlobalExceptionsFilter in the gateway(the sender)
Use in gateway(sender) controller

export interface IRpcException {
  message: string;
  status: number;
}

export class FitRpcException extends RpcException implements IRpcException {
  constructor(message: string, statusCode: HttpStatus) {
    super(message);
    this.initStatusCode(statusCode);
  }
  public status: number;

  private initStatusCode(statusCode) {
    this.status = statusCode;
  }
}

@Catch()
export class AllGlobalExceptionsFilter implements ExceptionFilter {
  constructor(private readonly httpAdapterHost: HttpAdapterHost) {}

  catch(exception: IRpcException, host: ArgumentsHost): void {
    const { httpAdapter } = this.httpAdapterHost;
    const ctx = host.switchToHttp();

    const httpStatus = exception.status
      ? exception.status
      : HttpStatus.INTERNAL_SERVER_ERROR;

    const responseBody = {
      statusCode: httpStatus,
      timestamp: new Date().toISOString(),
      path: httpAdapter.getRequestUrl(ctx.getRequest()),
      message: exception.message,
    };

    httpAdapter.reply(ctx.getResponse(), responseBody, httpStatus);
  }
}

@UseFilters(AllGlobalExceptionsFilter)

How to handle RpcException in NestJS

1 Answers