Not receiving messages in the reply queue that sent to RabbitMQ using amqplib and processed by NestJS - node.js

Question

So I'm using NestJS (v8) with the RabbitMQ transport (Transport.RMQ) to listen for messages
My NestJS code look something like this:
// main.ts
const app = await NestFactory.createMicroservice<MicroserviceOptions>(AppModule, {
transport: Transport.RMQ,
options: {
urls: ['amqp://localhost:5672'],
queue: 'my-queue',
replyQueue: 'my-reply-queue'
},
});
// my.controller.ts
import { Controller } from '#nestjs/common';
import { MessagePattern } from '#nestjs/microservices';
#Controller()
export class MyController {
#MessagePattern('something')
do(data: {source: string}): {source: string} {
console.log(data);
data.source += ' | MyController';
return data;
}
}
And in Node.JS application, I use amqplib to send to the NestJS application and receive the response
this is the code of the Node.JS application:
const queueName = 'my-queue';
const replyQueueName = 'my-reply-queue';
const amqplib = require('amqplib');
async function run() {
const conn = await amqplib.connect('amqp://localhost:5672');
const channel = await conn.createChannel();
await channel.assertQueue(queueName);
await channel.assertQueue(replyQueueName);
// Consumer: Listen to messages from the reply queue
await channel.consume(replyQueueName, (msg) => console.log(msg.content.toString()));
// Publisher: Send message to the queue
channel.sendToQueue(
queueName,
Buffer.from(
JSON.stringify({
pattern: 'something',
data: { source: 'node-application' },
})
),
{ replyTo: replyQueueName }
);
}
run()
When I run the node and the Nest.JS applications, the Nest.JS gets the message from the Node.JS publisher but the Node.JS consumer is never called with the reply

Answer 1

The fix was to add an id key in the data that the Node.JS application sends:
// ...
// Publisher: Send message to the queue
channel.sendToQueue(
queueName,
Buffer.from(
JSON.stringify({
// Add the `id` key here so the Node.js consumer will get the message in the reply queue
id: '',
pattern: 'something',
data: { source: 'node-application' },
})
),
{ replyTo: replyQueueName }
);
// ...
Detailed explanation (in Nest.JS source code)
This is because in the handleMessage function in server-rmq.ts file there is a check if id property of the message is undefined
// https://github.com/nestjs/nest/blob/026c1bd61c561a3ad24da425d6bca27d47567bfd/packages/microservices/server/server-rmq.ts#L139-L141
public async handleMessage(
message: Record<string, any>,
channel: any,
): Promise<void> {
// ...
if (isUndefined((packet as IncomingRequest).id)) {
return this.handleEvent(pattern, packet, rmqContext);
}
// ...
}
And there is no logic of sending messages to the reply queue in the handleEvent function, just handling the event