---
title: Message Queue
sidebar_position: 5
sidebar_custom_props:
  icon: TbSchema
---

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](https://github.com/timgit/pg-boss) under the hood.
2. `bull-mq`: this uses [bull-mq](https://bullmq.io/) 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
```ts
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
    });
  }
}

```

