RabbitMQ: dynamic subscription, queue and decorator values

[nidomiro]

I'm trying to make the topic of a subscription configurable [via NestJs Module-Initialization].

The problem is, decorators cannot use values available at Object creation time.

Is there a way to create a Subscription 'manually' and keep the benefits of the Decorator-variant (automatic reconnect, ...)?

[WonderPanda]

This is a major shortcoming of the NestJS configuration system and why I strongly suggest that configuration should occur separate from DI/Module initialization. The config package @golevelup/profiguration which I use for my own projects specifically gets bootstrapped at the start of your application before any imports are evaluated so you can actually use it to configure decorators.

The other option is to manually call dotenv.config at the top of your main entry point file at which point you should be able to reference process.env variables in your decorators

If you want to stick with your existing config system you can definitely manually set up subscriptions/rpc in module init. Just inject the AmqpConnection and call the methods directly

[federicogatti]

Hi @WonderPanda, thank you for your answer, but I don't understand how implement the second option (manually call dotenv.config). Do you have some useful references?

[WonderPanda]

You have to manually tell dotenv to parse your .env file at the top of your main script. This will ensure that process.env has been loaded before any other code is loaded which will allow you to use values from process.env inside of your decorators

@federicogatti Docs for config are here: https://github.com/motdotla/dotenv#config

[simplenotezy]

@WonderPanda Thanks for sharing this solution; that's what I ended up doing:

However, if I may, you seem experienced with Nest.js. Do you have any clue why they implemented such a cumbersome way of integrating something so simple as global environment variables? I really enjoy the framework so far, apart from maybe this, so I am really baffled by how complicated it really was.

[guicuton]

Hi guys,

I know this is a old discussion but I recently started to research this pack and as usual am I were reading some common issues/doubts, etc before to start to working with it and found this post.

Why just don't initialize the ConfigService class outside of the @Controller scope like:

// configuration.ts
export const configuration = () => ({
  NODE_ENV: process.env.NODE_ENV,
  RABBITMQ: {
    HTTP: {
      HOST: process.env.RABBITMQ_HTTP_HOST,
      PORT: process.env.RABBITMQ_HTTP_PORT,
      VHOST: process.env.RABBITMQ_HTTP_VHOST,
      USER: process.env.RABBITMQ_HTTP_USER,
      PASS: process.env.RABBITMQ_HTTP_PASS,
    },
    ROUTINGKEYS: {
      test: 'test',
    },
    EXCHANGES: {
      test: 'test',
    },
    QUEUES: {
      vendor: {
        test: 'vendor-test',
      },
    },
  },
});

// controller.ts
const configService = new ConfigService(configuration);

@Controller()
export class BulksmsonlineController {
  @RabbitSubscribe({
    queue: configService.get('RABBITMQ.QUEUES.vendor.test'),
    exchange: configService.get('RABBITMQ.EXCHANGES.test'),
    routingKey: configService.get('RABBITMQ.ROUTING.test'),
    queueOptions: {
      durable: true,
    },
  })

There is some drawback use it on this way?

[ahmetonurslmz]

here my solution for these cases. Currently i use nestjs's built-in config module but i couldn't use it while declaring queue listener and i solved the problem by creating another class. Simply import it and use anywhere you want.

I know it is simple and easy but wanted to share it in case somebody thinks solution for the problem :)

import * as dotenv from 'dotenv';

dotenv.config({
  path: '.env',
});

class Queues {
  public readonly listening: {
    QUEUE_NAME: string;
  };
  public readonly remote: { QUEUE_NAME: string };

  constructor() {
    this.remote = {
      QUEUE_NAME: this.prepare('queue_name'),
    };
    this.listening = {
      QUEUE_NAME: this.prepare('queue_name'),
    };
  }

  private prepare(queueName: string) {
    const mqType = process.env.MQ_TYPE;
    if (mqType === 'development') {
      return `${queueName}_${mqType}`;
    }
    return queueName;
  }
}

export const QUEUES = new Queues();