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Core Command

Introduction

The command micro service (often called the command and control micro service) enables the issuance of commands or actions to devices on behalf of:

  • other micro services within Edge Xpert (for example, an edge analytics or rules engine micro service)
  • other applications that may exist on the same system with Edge Xpert (for example, a management agent that needs to shutoff a sensor)
  • To any external system that needs to command those devices (for example, a cloud-based application that determined the need to modify the settings on a collection of devices)

The command micro service exposes the commands in a common, normalized way to simplify communications with the devices. There are two types of commands that can be sent to a device.

  • a GET command requests data from the device. This is often used to request the latest sensor reading from the device.
  • SET commands request to take action or actuate the device or to set some configuration on the device.

In most cases, GET commands are simple requests for the latest sensor reading from the device. Therefore, the request is often parameter-less (requiring no parameters or body in the request). SET commands require a request body where the body provides a key/value pair array of values used as parameters in the request (i.e. {"additionalProp1": "string", "additionalProp2": "string"}).

Note

v2.1 supports a new value type, Object, to present the structral value instead of encoding it as string for both SET and GET commands, for example, the SET command parameter might be {"Location": {"latitude": 39.67872546666667, "longitude": -104.97710646666667}}.

The command micro service gets its knowledge about the devices from the metadata service. The command service always relays commands (GET or SET) to the devices through the device service. The command service never communicates directly to a device. Therefore, the command micro service is a proxy service for command or action requests from the north side of Edge Xpert (such as analytic or application services) to the protocol-specific device service and associated device.

While not currently part of its duties, the command service could provide a layer of protection around device. Additional security could be added that would not allow unwarranted interaction with the devices (via device service). The command service could also regulate the number of requests on a device do not overwhelm the device - perhaps even caching responses so as to avoid waking a device unless necessary.

Data Model

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Note

While the general concepts of core command's GET/PUT requests are the same, the core command request/response models has changed significantly in Edge Xpert 2.0. Consult the API documentation for details.

Data Dictionary

Property Description
Id uniquely identifies the device, a UUID for example
Description
Name Name for identifying a device
Manufacturer Manufacturer of the device
Model Model of the device
Labels Labels used to search for groups of profiles
DeviceResources deviceResource collection
DeviceCommands collect of deviceCommand
Property Description
DeviceName reference to a device by name
ProfileName reference to a device profile by name
CoreCommands array of core commands
Property Description
Name
Get bool indicating a get command
Set bool indicating a set command
Path
Url
Parameters array of core command parameters
Property Description
ResourceName
ValueType

Configuration Properties

Please refer to the general Common Configuration documentation for configuration properties common to all services. Core Command no longer has any additional settings.

V2 Configuration Migration Guide

Refer to the Common Configuration Migration Guide for details on migrating the common configuration sections such as Service.

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