KubeEdge supports device management with the help of Kubernetes CRDs and a Device Mapper (explained below) corresponding to the device being used. We currently manage devices from the cloud and synchronize the device updates between edge nodes and cloud, with the help of device controller and device twin modules.
Device Management features are updated from v1alpha1 to v1alpha2 in release v1.4. It is not compatible for v1alpha1 and v1alpha2. Details can be found device-management-enhance
device model describes the device properties such as ‘temperature’ or ‘pressure’. A device model is like a reusable template using which many devices can be created and managed.
Details on device model definition can be found here.
Device Model Sample
A sample device model like below,
apiVersion: devices.kubeedge.io/v1alpha2 kind: DeviceModel metadata: name: sensor-tag-model namespace: default spec: properties: - name: temperature description: temperature in degree celsius type: int: accessMode: ReadWrite maximum: 100 unit: degree celsius - name: temperature-enable description: enable data collection of temperature sensor type: string: accessMode: ReadWrite defaultValue: 'OFF'
device instance represents an actual device object. It is like an instantiation of the
device model and references properties defined in the model which exposed by property visitors to access. The device spec is static while the device status contains dynamically changing data like the desired state of a device property and the state reported by the device.
Details on device instance definition can be found here.
Device Instance Sample
A sample device instance like below,
apiVersion: devices.kubeedge.io/v1alpha2 kind: Device metadata: name: sensor-tag-instance-01 labels: description: TISimplelinkSensorTag manufacturer: TexasInstruments model: CC2650 spec: deviceModelRef: name: sensor-tag-model protocol: modbus: slaveID: 1 common: com: serialPort: '1' baudRate: 115200 dataBits: 8 parity: even stopBits: 1 nodeSelector: nodeSelectorTerms: - matchExpressions: - key: '' operator: In values: - node1 propertyVisitors: - propertyName: temperature modbus: register: CoilRegister offset: 2 limit: 1 scale: 1 isSwap: true isRegisterSwap: true - propertyName: temperature-enable modbus: register: DiscreteInputRegister offset: 3 limit: 1 scale: 1.0 isSwap: true isRegisterSwap: true status: twins: - propertyName: temperature reported: metadata: timestamp: '1550049403598' type: int value: '10' desired: metadata: timestamp: '1550049403598' type: int value: '15'
Customized Protocols and Customized Settings
From KubeEdge v1.4, we can support customized protocols and customized settings, samples like below
propertyVisitors: - propertyName: temperature collectCycle: 500000000 reportCycle: 1000000000 customizedProtocol: protocolName: MY-TEST-PROTOCOL configData: def1: def1-val def2: def2-val def3: innerDef1: idef-val
protocol: common: ... customizedValues: def1: def1-val def2: def2-val
From KubeEdge v1.4, we add data section defined in device spec. Data section describe a list of time-series properties which will be reported by mappers to edge MQTT broker and should be processed in edge.
apiVersion: devices.kubeedge.io/v1alpha1 kind: Device metadata: ... spec: deviceModelRef: ... protocol: ... nodeSelector: ... propertyVisitors: ... data: dataTopic: "$ke/events/device/+/data/update" dataProperties: - propertyName: pressure metadata: type: int - propertyName: temperature metadata: type: int
Mapper is an application that is used to connect and control devices. Following are the responsibilities of mapper: 1) Scan and connect to the device. 2) Report the actual state of twin-attributes of device. 3) Map the expected state of device-twin to actual state of device-twin. 4) Collect telemetry data from device. 5) Convert readings from device to format accepted by KubeEdge. 6) Schedule actions on the device. 7) Check health of the device.
Mapper can be specific to a protocol where standards are defined i.e Bluetooth, Zigbee, etc or specific to a device if it a custom protocol.
Mapper design details can be found here
An example of a mapper application created to support bluetooth protocol can be found here
Usage of Device CRD
The following are the steps to
Create a device model in the cloud node.
kubectl apply -f <path to device model yaml>
Create a device instance in the cloud node.
kubectl apply -f <path to device instance yaml>
Note: Creation of device instance will also lead to the creation of a config map which will contain information about the devices which are required by the mapper applications The name of the config map will be as follows: device-profile-config-< edge node name >. The updates of the config map is handled internally by the device controller.
Run the mapper application corresponding to your protocol.
Edit the status section of the device instance yaml created in step 2 and apply the yaml to change the state of device twin. This change will be reflected at the edge, through the device controller and device twin modules. Based on the updated value of device twin at the edge the mapper will be able to perform its operation on the device.
The reported values of the device twin are updated by the mapper application at the edge and this data is synced back to the cloud by the device controller. User can view the update at the cloud by checking his device instance object.
Note: Sample device model and device instance for a few protocols can be found at $GOPATH/src/github.com/kubeedge/kubeedge/build/crd-samples/devices