NestJS - Microservices - Kafka Exception Handling - node.js

Question

I'm using NestJS to implement a microservice architecture, I'm using CLIENT app using NestJS,
The client app receives a rest request and sends to Kafka to get the result
try {
const pattern = 'findDoctors';
const payload = body;
const doctors = await lastValueFrom(
this.client.send(pattern, payload).pipe(timeout(50000)),
);
return doctors;
} catch (e) {
console.log(e);
throw new Error(e);
}
And in the microservice side (Hybrid Application for now, will remove the rest apis later)
#MessagePattern('findDoctors')
findDoctors(#Payload() message): any {
return this.doctorService.searchForDoctors(message.value);
}
async searchForDoctors(data): Promise<any[]> {
this.logger.info('Started search for doctors job');
throw 'Not Found';
}
After i throw the exception i get in the logs
node:17720) UnhandledPromiseRejectionWarning: TypeError [ERR_INVALID_ARG_TYPE]: The first argument must be of type string or an instance of Buffer, ArrayBuffer, or Array or an Array-like Object. Received an instance of Object
at Function.from (buffer.js:330:9)
at ServerKafka.assignErrorHeader (C:\Users\Desktop\Projects\node_modules\#nestjs\microservices\server\server-kafka.js:137:73)
at ServerKafka.sendMessage (C:\Users\Desktop\Projects\node_modules\#nestjs\microservices\server\server-kafka.js:119:14)
at C:\Users\Desktop\Projects\node_modules\#nestjs\microservices\server\server-kafka.js:81:31
at C:\Users\Desktop\node_modules\#nestjs\microservices\server\server.js:46:31
at processTicksAndRejections (internal/process/task_queues.js:79:11)
(node:17720) UnhandledPromiseRejectionWarning: Unhandled promise rejection. 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(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 3)
(node:17720) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
and the client side just waits to timeout and never receive an exception response from the micro service
Tried using RpcException but it's the same

Answer 1

Found the answer
used
return new RpcException('not found');
instead of
throw new RpcException('not found')
throwing the exception needs an exception filter to catch it
#Catch(RpcException)
export class ExceptionFilter implements RpcExceptionFilter<RpcException> {
catch(exception: RpcException, host: ArgumentsHost): Observable<any> {
return throwError(exception.getError());
}
}
and in the client side you can catch the error when using filters and return a normal http exception, or use filters on that too
#Post('/search')
async findAll(#Body() body) {
console.log('Sending kafka msg');
try {
const doctors = await this.doctorService.findDoctors(body);
return doctors;
} catch (e) {
console.log(e)
throw new HttpException({
status: '500',
error: e.message,
}, 500)
}
}