Google Core IoT Device Offline Event or Connection Status

Question

Does anybody know of an easy way to trigger an event when a device on Google Core IoT goes offline? Before I switched to Google's IoT implementation, this was very easily handled by triggering an event when MQTT disconnects, but it seems Google has no easy way of doing this.

Does anybody know if there is something planned for this?

Who's back do I need to scratch to get them to see that something like this is a basic requirement for IoT device management!

Other platforms like AWS and Microsoft already have this implemented (or some way to handle it easily): https://docs.aws.amazon.com/iot/latest/developerguide/life-cycle-events.html

Device connectivity(online/offline)status with the Auzure iot hub

I wish I had known this before writing all my code and implementing my setup using Google's IoT platform, I guess that's my fault for assuming something so simple and that should be standard for IoT devices would be available.

How are you going to compete with other IoT providers if you can't even provide basic offline/online events?!

My reply in this SO question shows how I had to write 100+ lines of code just to create a firebase function to check if a device is online (but that still doesn't handle offline events, and is just a hack for something that should be native to ANY IoT service provider!): https://stackoverflow.com/a/54609628/378506

I'm hoping someone else has figured out a way to do this, as i've spent numerous days searching SO, Google, Google Core IoT Documentation, and still have not found anything.

Even if MQTT Last Will was supported we could make that work, but even that IS NOT SUPPORTED by Google (https://cloud.google.com/iot/docs/requirements) ... come on guys!

Answer 1

Your cloud project does have access to the individual MQTT connect/disconnect events, but currently they only show up in the Stackdriver logs. Within the cloud console, you can create an exporter that will publish these events to a Pub/Sub topic:

1. Visit the Stackdriver Logs in the Cloud Console.

2. Enter the following advanced filter:

   resource.type="cloudiot_device"
   jsonPayload.eventType="DISCONNECT" OR "CONNECT"
   

3. Click CREATE EXPORT

4. Enter a value for Sink Name
5. Select Cloud Pub/Sub for Sink Service
6. Create a new Cloud Pub/Sub topic as the Sink Destination

The exporter publishes the full LogEntry, which you can then consume from a cloud function subscribed to the same Pub/Sub topic:

export const checkDeviceOnline = functions.pubsub.topic('online-state').onPublish(async (message) => {
  const logEntry = JSON.parse(Buffer.from(message.data, 'base64').toString());
  const deviceId = logEntry.labels.device_id;

  let online;
  switch (logEntry.jsonPayload.eventType) {
    case 'CONNECT':
      online = true;
      break;
    case 'DISCONNECT':
      online = false;
      break;
    default:
      throw new Error('Invalid message type');
  }

  // ...write updated state to Firebase...

});

Note that in cases of connectivity loss, the time lag between the device being unreachable and an actual DISCONNECT event could be as long the MQTT keep-alive interval. If you need an immediate check on whether a device is reachable, you can send a command to that device.