Timeseries Data

You can update Asset / Data Stream data values on the Kelvin Cloud from the Kelvin SmartApp™.

Structure

Define Data Stream Names

In order to publish an output Data Message, the first requirement is to add the intended Data Stream names to the outputs to the app.yaml as follows:

app:
  type: kelvin
  kelvin:

    outputs:
    - data_type: number
      name: motor_temperature_fahrenheit

    - data_type: boolean
      name: motor_error

    - data_type: string
      name: motor_error_description

    - data_type: object
      name: gps_data

Define Asset Names

The Asset name can only be related to any Assets associated with the Kelvin SmartApp™ workload.

Note

Any attempt to write to Assets not associated with the Kelvin SmartApp™ workload will be dropped and an error recorded in the logs.

Timeseries Data Messages

Output (Number/Boolean/String/Object) Objects support the following attribute:

Attribute	Required	Description
`payload`	required	Number, Boolean, String or object value, depending on the `data_type`

You need to create and publish each output Data Message according to the Asset / Data Stream's data_type.

NumberBooleanStringObject

from kelvin.message import Number
from kelvin.krn import KRNAssetDataStream

(...)

# Create and Publish a Number
await app.publish(
    Number(resource=KRNAssetDataStream(asset, "motor_temperature_fahrenheit"), payload=97.3)
)

from kelvin.message import Boolean
from kelvin.krn import KRNAssetDataStream

(...)

# Create and Publish a Boolean
await app.publish(
    Boolean(resource=KRNAssetDataStream(asset, "motor_error"), payload=True)
)

from kelvin.message import String
from kelvin.krn import KRNAssetDataStream

(...)

# Create and Publish a String
await app.publish(
    String(resource=KRNAssetDataStream(asset, "motor_error_description"), payload="Temperature is too high")
)

For objects, the payload is an arbitrary dict with any given dict structure.

from kelvin.message import String
from kelvin.krn import KRNAssetDataStream

(...)

# Create and Publish an Object
gpsd_dict = {
"latitude": 90,
"longitude": 100
}

await app.publish(
    Message(
    type=KMessageTypeData(primitive="object", icd="gps"),
    resource=KRNAssetDataStream(asset, datastream),
    payload=gps_dict,
    )
)