How to implement rabbit mq or bull js in loopback 4 - loopbackjs

Question

I am trying to implement a background service so that there is less load on the API call. Background task will run to upload files to S3 and send email using nodemailer.

Answer 1

Following the loopback 4's design patterns you can create a service provider and inject it in your service or controller.
Here is a very basic example with Bull.js:
import Bull, { Queue, Job } from "bull";
import {Provider, service} from "#loopback/core";
import {get} from "#loopback/rest";
export function audioProcessor(job: Job) {
console.log(
`Processing audio file: ${job.data.filename}`,
`Audio bitrate: ${job.data.bitrate}`
);
}
export class AudioQueueProvider implements Provider<Queue> {
async value() {
const queue = new Bull("AudioQueue", {
redis: { port: 6379, host: "127.0.0.1" }
});
queue.process(audioProcessor);
return queue;
}
}
export class AudioController {
constructor(
#service(AudioQueueProvider) public queue: Queue;
) {}
#get('/process-audio')
async addToQueue(): Promise<string> {
await this.queue.add(
{
filename: 'process_me.wav',
bitrate: 320,
}
);
return 'Audio file added to the AudioQueue for processing';
}
}
The RabbitMQ implementation should be similar (not tested):
import { Provider, service } from "#loopback/core";
import {get} from "#loopback/rest";
import amqp from "amqplib/callback_api";
export function audioProcessor(msg: any) {
console.log(
`Processing audio file: ${msg.content.filename}`,
`Audio bitrate: ${msg.content.bitrate}`
);
}
export class AudioQueueProvider implements Provider<any> {
async value() {
const CONN_URL = "amqp://localhost";
let ch = null;
const channelName = 'AudioQueue';
amqp.connect(CONN_URL, function (err, conn) {
conn.createChannel(function (err, channel) {
ch = channel;
});
});
ch.assertQueue(channelName, {
durable: false
});
ch.consume(channelName, audioProcessor, {
noAck: true
});
return ch;
}
}
export class AudioController {
constructor(
#service(AudioQueueProvider) public channel: any;
) {}
#get('/process-audio')
async addToQueue(): Promise<string> {
await this.channel.sendToQueue(
'AudioQueue',
{
filename: 'process_me.wav',
bitrate: 320,
}
);
return 'Audio file added to the AudioQueue for processing';
}
}