34. Metric Harvester Filter¶
The Metric Harvester filter provides a way to capture properties from datum generated by data sources as metrics.
This filter is provided by the Metrics Harvester plugin, which is included in the solarnode-app-metrics-harvester package in SolarNodeOS.
34.1 Settings¶
In addition to the Common Settings, the following general settings are available:
| Setting | Description |
|---|---|
| Properties | A list of datum property configurations. See Property settings for more information. |
| Expressions | A list of expression configurations. See Expression settings for more information. |
34.2 Property settings¶
Use the Properties + and - buttons to add/remove property configurations. Each property configuration contains the following settings:
| Setting | Description |
|---|---|
| Property Type | The type of the datum property to extract. |
| Property | The name of the datum property to extract. Only numeric properties are supported. |
| Unit Offset | An offset to add to the value. This is the first transform applied. Set to 0 for no offset. |
| Unit Multiplier | A multiplication factor to normalize the value into some other unit. This is the second transform applied, after the Unit Offset. Set to 1 to leave the input unchanged. |
| Multiplier | A multiplication factor to normalize the value into some other unit. This is the third transform applied, after the Unit Multiplier. Set to 1 to leave the input unchanged. |
| Offset | An offset to add to the value. This is the forth transform applied, after the Multiplier. Set to 0 for no offset. |
| Metric Name | The metric name to assign to the value. |
34.2.1 Value transform¶
The various Multiplier and Offset settings allow you to apply two linear equations to the datum property values to transform a raw data value x into a corresponding metric value y.
First the Unit Offset B and Unit Multiplier M are applied using the equation
y = (x + B) × M
Then the Multiplier m and Offset b are applied using the equation
y = (m × x) + b
Taken together, the overal equation applied is thus:
y = (m × ((x + B) × M)) + b
34.3 Expression settings¶
Use the Expressions + and - buttons to add/remove property configurations. Each expression configuration contains the following settings:
| Setting | Description |
|---|---|
| Metric Name | The metric name to assign to the value. |
| Expression | The expression to evaluate. See Expressions for more info. |
| Expression Language | The expression language to write Expression in. |