mongodb-mqtt-wisepaas

This is a data-worker app refers to mongodb and rabbitmq on cloud.

Quick Start

STEP 1 Login to WISE-PaaS via command line cf login with your domain, username & password.

STEP 2 Push the app

cf push

NOTE: This automatically binds to the services in the manifest.yml.

If you did not include the service instances in the manifest file, you would need to proceed step 3.

---
applications:   
- name: mongodb-mqtt-demo
  memory: 128M
  disk_quota: 128M
  instances: 1
  buildpack: nodejs_buildpack
  health-check-type: http
  timeout: 30
  services:
   - mongodb
   - rabbitmq

STEP 3 Bind the app to the assigned group

Bind app to services

cf bs {appName} {serviceInstanceName}

NOTE: When you are binding an app to a service, remember to use service instance name.

The app start automatically if the push is successful, and the state of your app should be running.

If you bind your app manually, you would need to restart your app cf restage {appName}.

Paste your route on a browser to check your results.

You should get this:

Under the home route, you would get some text.

And under the "/hbts" route, you would see the data queried from the database.

If you don't have any data yet, you would just see an empty array.

Code description

Part 1. Get variables of MongoDB and connect to database

const vcap_services = JSON.parse(process.env.VCAP_SERVICES);
const replicaSetName = vcap_services['mongodb-innoworks'][0].credentials.replicaSetName;
const db = vcap_services['mongodb-innoworks'][0].credentials.uri + '?replicaSet=' + replicaSetName;

mongoose.connect(db)
  .then(() => console.log('Connected to the MongoDB...'))
  .catch(err => console.log('Could not connect to MongoDB...', err));

NOTE: 'mongodb-innoworks' is the service name, not service instance name. To check service name, please login to WISE-PaaS Management Portal or command line: cf services

Part 2. Get variables of Rabbitmq

// -- Get env variables for rabbitmq service
const vcapServices = JSON.parse(process.env.VCAP_SERVICES);
const mqttUri = vcapServices['p-rabbitmq'][0].credentials.protocols.mqtt.uri

Note: Just the same as above, 'p-rabbitmq' is the service name, not service instance name. To check service name, please login to WISE-PaaS Management Portal or command line: cf services

Part 3. Create Schema for the data

const hbtSchema = new mongoose.Schema({
  ts: {
    type: Date,
    default: Date.now
  },
  heartbeat: Number,
  patient: {
    type: String,
    default: 'patient-test'
  }
});

const heartbeat = mongoose.model('heartbeat', hbtSchema);

NOTE: This part creates the schema of the data.

NOTE: Remember to include the entry 'ts', which is timestamp.

This is crucial for future work, so that we could set up the MongoDB data source for WISE-PaaS Dashboard.

Part 4. Subscribe to a topic and listen

const client = mqtt.connect(mqttUri);

// Subscribe
client.on('connect', (connack) => {
  client.subscribe('ward/heartbeat', (err, granted) => {
    if (err) console.log(err);

    console.log('@' + formatTime() + ' -- Subscribed to the topic: ward/heartbeat');
  });
});

// Receiving data
client.on('message', (topic, message, packet) => {
  let time = formatTime();
  console.log(`@${time} -- Got data from: ${topic}`);

  // mock heartbeat data
  const hbt = message.toString();
  const newHbt = new heartbeat({
    heartbeat: hbt
  });

  newHbt.save(function(err){
    if(err){
      console.log(err);
    }else{
      console.log('saved');
    }
  });
});

NOTE: This part subscribes the app to the topic we assigned and receives data from it, then passes it to the database.