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

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.