Queues facilitate async operations to be performed. They can be used for performing background tasks such as sending a welcome email on register. Each use case will have its own queue class extended from MessageQueueServiceBase.

Currently, queue supports two drivers which can be configurred by env variable MESSAGE_QUEUE_TYPE.

1. pg-boss: this is the default driver, which uses pg-boss under the hood.
2. bull-mq: this uses bull-mq under the hood.

Steps to create and use a new queue

1. Add a queue name for your new queue under enum MESSAGE_QUEUES.
2. Provide the factory implementation of the queue with the queue name as the dependency token.
3. Inject the queue that you created in the required module/service with the queue name as the dependency token.
4. Add worker class with token based injection just like producer.

Example usage

class Resolver {
  constructor(@Inject(MESSAGE_QUEUES.custom) private queue: MessageQueueService) {}

  async onSomeAction() {
    //business logic
    await this.queue.add(someData);
  }
}

//async worker
class CustomWorker {
  constructor(@Inject(MESSAGE_QUEUES.custom) private queue: MessageQueueService) {
    this.initWorker();
  }

  async initWorker() {
    await this.queue.work(async ({ id, data }) => {
      //worker logic
    });
  }
}

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