MQTT in Ember.js

Ember Octane mqtt.js

Less than 2 years ago I started a new project with the company I work for that requires to an Ember Octane app to control several connected IoT devices around the world. We choosed the MQTT publish/subscribe network protocol to interact with our on-field devices for its lightweight message structure and its limited network bandwith requirements.

After googling for a javascript MQTT library I’ve found the MQTT.js client. At the moment of my search the asynchronous version was not yet released, so I had to wrap the event based client into an Ember service and transform it into a Promise based client.

This is a mandatory requirement because I need broker connection before subscribing to a topic or I need topic subscription before publishing on it. Sometimes you had retain messages on a topic for receiving last published value after the subscription. Other times you need publishing an empty value on a topic to request the status of a given device. So you need working subscribtion on a topic before sending a message. That said javascript Promises are the only way to accomplish this tasks.

When I wrote this service I didn’t find an Ember addon ready to do this things. Therefore I decided to dive into the docs and learn how to build an addon. The ember-mqttjs addon is my first Ember addon!

The code

This service extends the Evented Ember object for raising events on new messages as well as connect, disconnect events and many others you can find on its readme. In addition of raising this events it returns a Promise for connect, subscribe, unsubscribe and publish methods.

This is an example of another service that uses the ember-mqttjs service:

import Service, { inject as service } from '@ember/service';
import { bind } from '@ember/runloop';

export default class YourService extends Service {
  @service mqtt;
  constructor() {
    super(...arguments);
    //...
    let _fOnMessage = bind(this, this._onMessage);
    this.mqtt.on('mqtt-message', _fOnMessage); 
  }

  _onMessage(sTopic, sMessage) {
    //code to manage messages received on a certain topic
  }

  async subscribeAndPublish(sTopic, sMessage) {
    try {
      await this.mqtt.connect(HOST, USERNAME, PASSWORD)
    } catch (oError) {
      //code on connection error
    }
    try {
      await this.mqtt.subscribe(sTopic);
    } catch (oError) {
      //code for subscription error
    }
    try {
      await this.mqtt.publish(sTopic, sMessage);
    } catch (oError) {
      //code for message publish error
    }
    return Promise.resolve();
  }
//...
}

I’ve just refactored the addon code to use async/await features and I moved the CI from travis to github action (thanks to this Jeldrik Haschke’s repo).
Many improvements can be done in the future starting from writing more tests to cover other cases.
If you have any suggestions or proposal to improve the code as well as the tests you are welcome!

Contact me or start contributing on GitHub project repo!

Ember + Boostrap 5

Today I welcome a new template for my blog by returning to write a post after a very long time!

This WordPress theme is built on top of the latest Bootstrap release, Bootstrap 5 and with this post I would like to explain you how to use this hugely popular front-end framework in an Ember app.

With this major new release the developers have focused most of their efforts towards removing jQuery as a dependency of the framework to make it lighter and usable by a wider audience now interested in saving as much kb as possible.

For those who knows and uses the previous Bootstrap version (v4) I suggest to dive into the migration guide, to understand what breaking changes were made in this new update.

As an experiment (I will tell you later about what I am working on in my spare time) I’ve tried to use Bootstrap 5 in a new Ember Octane app and thank to the release of the bootstrap npm package this turned out to be tremendously simple.

Let’s see the steps:

First you have to install the bootstrap npm package:

npm install --save-dev bootstrap

Then you have to modify your ember-cli-build.js file:

'use strict';

const EmberApp = require('ember-cli/lib/broccoli/ember-app');

module.exports = function (defaults) {
  let app = new EmberApp(defaults, {
    // Add options here
    sassOptions: {
      includePaths: ['node_modules/bootstrap/scss'],
    },
  });
  app.import('node_modules/bootstrap/dist/js/bootstrap.bundle.min.js');
  return app.toTree();
};

The last few steps are required to be able to import bootstrap SCSS files.
First you have to install ember-cli-sass addon:

ember install ember-cli-sass

Then you have to rename your app style app.css to app.scss and insert the line to import the bootstrap files:

@import 'bootstrap';

You are now ready to use Bootstrap 5 in your Ember app!