calculated fields

Triggers calculated field processing for incoming time series or attributes without persisting the data to the database.

Preconditions

The message type and data structure must correspond to your incoming data type:

• Time series data: Use POST_TELEMETRY_REQUEST with formats defined here
• Attributes data: Use POST_ATTRIBUTES_REQUEST with formats defined here

Configuration

This node has no configuration options.

JSON Schema

1
2
3
4
5
6
7
{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "EmptyNodeConfiguration",
  "type": "object",
  "properties": {},
  "additionalProperties": false
}

Message processing algorithm

1. The node examines the type of the incoming message.
2. For POST_TELEMETRY_REQUEST or POST_ATTRIBUTES_REQUEST messages:
   • Parses the time series or attribute data from the message data (including attribute scope from metadata when applicable)
   • Triggers the evaluation of any calculated fields that use this data
   • The incoming time series or attribute data itself is not persisted to the database
3. When calculated fields are evaluated:
   • A new message is generated with the originator whose calculated field state was updated
   • This new message is pushed into the root rule chain of the originator
4. After triggering calculated field processing, the original message is forwarded to the Success connection
5. If an unsupported message type is received or an error occurs, the message is routed to the Failure connection

Note: The calculated results are included in the newly generated message (step 3). To persist these results to the database, you still need to use a “save time series” or “save attributes” node in the rule chain.

Output connections

• Success
  • The message data contains valid time series or attribute data and calculated field processing was triggered
  • The message data is empty (no processing required)
• Failure
  • The incoming message type is not POST_TELEMETRY_REQUEST or POST_ATTRIBUTES_REQUEST
  • The incoming message data could not be parsed into time series data or attributes data
  • An unexpected error occurred during message processing

Examples

Example 1 — Processing time series for calculated fields

Incoming message

Type: POST_TELEMETRY_REQUEST

Data:

1
2
3
4
{
  "temperature": 25.5,
  "humidity": 60
}

Originator: DEVICE.

Node configuration

1
{}

State of the system

The device has a calculated field “heatIndex” defined that uses the formula: temperature + 0.5 * humidity

Outgoing message

The outgoing message is identical to the incoming one. Routed via the Success connection.

Result

The calculated field “heatIndex” is evaluated using the incoming temperature and humidity values (25.5 + 0.5 * 60 = 55.5). A new message containing the calculated value is generated with the device as the originator and pushed to the root rule chain. The original time series data (temperature and humidity) is not stored in the database.

Example 2 — Processing attributes for calculated fields

Incoming message

Type: POST_ATTRIBUTES_REQUEST

Data:

1
2
3
4
{
  "maxSpeed": 100,
  "currentSpeed": 75
}

Metadata:

1
2
3
{
  "scope": "SERVER_SCOPE"
}

Originator: DEVICE.

Node configuration

1
{}

State of the system

The device has a calculated field “speedPercentage” defined that calculates: (currentSpeed / maxSpeed) * 100

Outgoing message

The outgoing message is identical to the incoming one. Routed via the Success connection.

Result

The calculated field “speedPercentage” is evaluated (75 / 100 * 100 = 75%). A new message with the calculated value is generated and pushed to the root rule chain. The original attributes are not persisted to the database.

Example 3 — Empty payload handling

Incoming message

Type: POST_TELEMETRY_REQUEST

Data: {}

Node configuration

1
{}

Outgoing message

The outgoing message is identical to the incoming one. Routed via the Success connection.

Result

No calculated fields are triggered since the data is empty. The message passes through successfully without any processing.

Example 4 — Unsupported message type

Incoming message

Type: ENTITY_CREATED

Node configuration

1
{}

Outgoing message

The outgoing message is identical to the incoming one. Routed via the Failure connection.

Result

The processing fails because the node only supports POST_TELEMETRY_REQUEST and POST_ATTRIBUTES_REQUEST message types. ENTITY_CREATED lifecycle events cannot trigger calculated field processing.