Core Data Service APIs

The Core Data microservice provides a centralized persistence facility for data readings collected by devices and sensors.

Content

• Core Data's purpose

• Event & Reading

• REST API outline

• Reference

Core Data’s Purpose

• Provides a centralized persistence facility for data readings collected by devices and sensors.

• Device services for devices and sensors that collect data, call on Core Data to store the device and sensor data on the edge system (such as a gateway)

  • Allows for store and forward technology

  • Supports actuation decisions at the edge

• Data is stored until…

  • It can be moved "north" and exported to Enterprise and cloud systems

  • It is “scrubbed” to make way for new sensor data

• Provides an API that other services can use to access the historical data

  • Should be used sparingly as not to impact data collection

Event & Reading

• Events are collections of Readings

  • Associated to a device

• Readings represent a sensing on the part of a device/sensor

  • Simple Key/Value pair

  • Key is a value descriptor

  • Value is the sensed value

  • Ex: Temperature: 72

• Event would need to have one Reading to make sense

REST API Outline

• Event APIs

  • DELETE – should really only be used by data clean up facilities

  • GET’s galore to query for Events, by

    • id

    • Associated Device

    • timestamp (range start & end)

    • Associated Device and Reading with particular Value Descriptor

  • GET Event count

• Reading APIs

  • GET’s galore to query for Readings, by

    • id

    • Associated Device (via Event)

    • uomLabel (of associated Value Descriptor)

    • label (of associated Value Descriptor)

    • type (of associated Value Descriptor)

    • Timestamp (via Event)

  • GET Reading count (good debug/checking mechanism)

Some API examples

GET Event Count

http://localhost:48080/api/v1/event/count/{deviceId}

Return a count of the number of events in core data for a given device - identified by id or name.

GET Events

http://localhost:48080/api/v1/event/device/{deviceId}/{limit}

Return list of events with their associated readings for a given device, sort by event creation date.

DELETE Events by deviceId

http://localhost:48080/api/v1/event/device/{deviceId}

Delete all events (and their readings) associated to a device given the device's id (either database generated id or name).

DELETE All Events

http://localhost:48080/api/v1/event/scrub

Remove all pushed events and their associated readings.

GET Reading by device

http://localhost:48080/api/v1/reading/device/{deviceId}/{limit}

Return list of all readings for a given device, sort by reading creation date.

GET Reading by value descriptor and device

http://localhost:48080/api/v1/reading/name/{name}/device/{deviceId}/{limit}

Return a list of readings that are associated to a ValueDescripter by name and Device by name (or id).

Reference

Core-data API document link: https://docs.edgexfoundry.org/core-data.html