IoT Device Twin Service

The Device Twin service holds information about the state of the connected devices. Once a device is registered in the IoT Identity Service, a device twin it created to hold the current and desired state of the device.

The device twin record holds:

• Summary of the device
• Last known heartbeat from the device
• The groups that the device belongs to
• Details about the device's state
• Details about the device's desired state

The service provides a cache so the devices can be monitored by the IoT Management Service, and relays actions to the device IoT agent e.g. to install a new application.

Design

Build

go build -o devicetwin bin/devicetwin/devicetwin.go

Configuration

Default values are loaded first. Those can be seen here in defaultValues.

Configuration can be provided by configuration yaml or environment variables. The configuration file path is specified by an environment variable CONFIG_FILE_PATH. It will also look in the current directory by default without specifying anything. If it finds a config.yaml then it will load those values.

Environment variables will override any previous specified values. Environment variables are the YAML keys in uppercase with periods replaced with underscores and prefaced with IOTDEVICETWIN_. Ex. database.driver becomes IOTDEVICETWIN_DATABASE_DRIVER as an environment variable. Additional examples can be seen in the Kubernetes YAML here.

Keys

Keys and descriptions can be found here.

Run

go run bin/devicetwin/devicetwin.go 

The service connects to the MQTT Broker using the certificates found in the directory specified by the service.certificates.path value. Its default value is /srv/certs. The filenames of the certificates have default values of ca.crt, server.crt and server.key. They can be modified by setting the values for mqtt.root.ca.filename, mqtt.client.certificate.filename and mqtt.client.key.filename respectively.