Microservice NodeJs RabbitMQ

api.js

'use strict';

const express = require('express');
const app = express();
const port = process.env.PORT || 4001;

const rabbit = {
  generateMessage: function(nbMessage) {
    let lists = [];
    for (let i = 0; i < nbMessage; i++) {
      lists.push({
        message: `ID ${i}`
      });
    }

    return lists;
  },

  publishList: function(listContent, callback) {
    const amqpUrl = `amqp://${process.env.RABBITMQ_USER}:${process.env.RABBITMQ_PASSWORD}@${process.env.RABBITMQ_HOST}${process.env.RABBITMQ_VHOST}`;
    return amqplib.connect(amqpUrl).then(function(conn) {
      return conn.createChannel().then(function(ch) {
        const ok = ch.assertQueue(process.env.QUEUE, {durable: true});
        return ok.then(function(_qok) {
          listContent.forEach((content) => {
            ch.sendToQueue(process.env.QUEUE, new Buffer(JSON.stringify(content)));
          });

          return ch.close();
        });
      }).finally(function() { conn.close(); });
    }).catch(console.warn.bind(this, "catch"));
  },
};

app.get('/messages/:nbMessage', (req, res) => {
  // Generate messages
  const messages = rabbit.generateMessage(req.params.nbMessage);

  // Publish message to queue
  return rabbit.publishList(messages).then(() => {
    res.json({
      status: 'success',
      nbMessage: req.params.nbMessage
    });
  });
});

app.listen(port, () => {
  console.log('Server started: ' + port);
});

microservice.js

'use strict';

const amqplib = require('amqplib');

const amqpUrl = `amqp://${process.env.RABBITMQ_USER}:${process.env.RABBITMQ_PASSWORD}@${process.env.RABBITMQ_HOST}${process.env.RABBITMQ_VHOST}`;
const rabbitmqConnection = amqplib.connect(amqpUrl);

rabbitmqConnection.then((conn) => {
  return conn.createChannel();
}).then((ch) => {
  // One by one message
  ch.qos(1);
  return ch.assertQueue(process.env.QUEUE, {durable: true}).then(() => {
    return ch.consume(process.env.QUEUE, (msg) => {
      handler(msg.content.toString(), () => {
        const currentdate = new Date();
        console.log(` => Callback at : ${currentdate.toLocaleTimeString()}`);
        // Message is done
        ch.ack(msg);
      });
    }, {noAck: false});
  });
}).catch(console.warn);

const handler = (message, callback) => {
  // Handle message
  console.log(`Message : ${message}`);

  // Execute callback
  callback();
};