This topic provides detailed information about the Action Runner scripting language that you can use to implement logic in Edge Actions that run on Octave edge devices at the edge.

JavaScript Environment

The Action Runner runs the appropriate Actions when their configured triggers are received from the Data Hub.

ECMAScript 5

The environment that executes your code is in strict mode, a restricted subset of JavaScript 5.1. For more information, read the documentation.

With this version you should avoid declaring global variables (use var x = 1; instead of just simply x = 1;). For more information about strict mode, read the Mozilla Developer Network article.

We do not support most features of ECMAScript 6 and we also disallow the use of eval. If you are not familiar with JavaScript, get started in a few minutes with the following resources:

• Learn JavaScript with learnxinyminutes.com
• JavaScript in 14 minutes

Format

Structure

The Action is a standard ECMAScript 5.1 function, with arity-1:

function ( payload ) {
}

Valid input payload consists of any valid JSON element:

• JSON Boolean
• JSON Number
• JSON String
• JSON Object
• JSON Array

Output

Each Action should return a value. If no value is returned, no further work needs to be done. If a value is returned, Action Runner validates it to match the following JSON format:

result = {
     key1 : [ value1, value2, … , valueN],
     key2 : [ … ],
     …
     keyN : [ … ]
}

Each value must be in an array of key/value pairs.

The “keys” specify the target to deliver the payloads. Each key is a URI, comprised of a scheme (), a separator (://), and a path () - i.e. ://. The available key types are:

The “values” are the data to output. Each “value” can be any JSON type (boolean, number, string, object, array).

📘

Note

Events sent from an Edge Action cannot be sent to a named Stream in the Cloud, they will be stored in the :/default Stream of the device.

Each <destination>://<path> entry must be unique.

Errors and Failures

• If an Action fails validation at compilation (load) time, it cannot be loaded. If it is the sole Action to specify that topic, Octave remove the callback handler for that topic.
• If an Action fails while executing, an error should be logged, and a value should be written to the Data Hub.
• If a single output “key” or “value” fails validation, Octave proceeds with the other keys and values and continue to process those which are valid.

Octave Functions

The following JavaScript functions are provided within the environment.

📘

Note

It's recommended that the functions listed below in firmware 3.1.0+ be used where possible.

Functions Available in Firmware 3.1.0+:

• Resource.readValue(): Reads the current value of a Resource.
• Resource.read(): Reads the current value of a resource and returns it as a tuple (value and timestamp).
• Observation.getMax(): Gets the maximum value of an Observation's buffer.
• Observation.getMin(): Gets the minimum value of an Observation's buffer.
• Observation.getMean(): Gets the mean value of an Observation's buffer.
• Observation.getBuffer(): Extracts the raw buffer values from an Observation.

Functions Available in all Firmware Versions:

• Datahub.read(): Performs a read operation on the Data Hub (e.g., to read the value of a resource).
• Datahub.query(): Performs a query operation which reads the min, max, mean, or standard deviation of a value on the Data Hub.

Resource.readValue()

Reads and returns the current value of a Resource.

This function is available in firmware 3.1.0+.

Parameters

Returns

The current value of the Resource.

Example

Request

var result = Resource.readValue('/redSensor/light/value');

Response

988

Resource.read()

Reads the current value of a Resource.

This function is available in firmware 3.1.0+.

Parameters

Returns

Example

Request

var result = Resource.read('/redSensor/light/value');

Response

{
    "value": 1291,
    "timestamp": 1606159021.780723
}

Observation.getMax()

Returns the maximum value in an Observation's buffer.

This function is available in firmware 3.1.0+.

Parameters

Returns

The resulting data will be a scalar, or null if the buffer is empty.

Example

Request

var result = Observation.getMin('light', 10);

Response

780

Observation.getMin()

Returns the minimum value in an Observation's buffer.

This function is available in firmware 3.1.0+.

Parameters

Returns

The resulting data will be a scalar, or null of the buffer is empty.

Example

Request

var result = Observation.getMax('light', 10);

Response

900

Observation.getMean()

Returns the mean value in an Observation's buffer.

This function is available in firmware 3.1.0+.

Parameters

Returns

The resulting data will be a scalar, or null of the buffer is empty.

Example

Request

var result = Observation.getMean('light', 10);

Response

890

Observation.getBuffer()

Extracts the raw buffer from an Observation.

This function is available in firmware 3.1.0+.

Parameters

Returns

An array of value/timestamp pairs:

Example

Request

var result = Observation.getBuffer('light');

Response

[
  {"v" : 254, "t" : 1234567890},
  {"v" : 259, "t" : 1233563449}
]

Datahub.read()

Performs a read operation on the Data Hub (e.g. to read the value of a Resource).

Parameters

Returns

The resulting data will be in JSON format, with two field names:

Example 1

Request

For regular Resources, <data name> is the terminating node of the path provided. For example:

var result = Datahub.read('/io/ADC0/period', 0)

Response

{
    "period" : 300,
    timestamp : 1292947293
}

Example 2

Request

For user-defined Resources, the terminating node of the path is always "value". For example:

var result = Datahub.read("/redSensor/light/value",0);

Response

{
    "value" : 254,
    timestamp : 1234567890
}

Datahub.query()

Performs a query operation which reads the min, max, mean, or standard deviation of a value on the Data Hub.

Parameters

Returns

The resulting data will be a scalar.

Example

Request

var queryResult = Datahub.query('my_observation', 'mean', 10000)

Response

32

Manipulating Binary Data

Often times it necessary to manipulate data such as that read from Modbus (e.g., to change endianness). This is can be done in an Edge Action or, less commonly, in a Cloud Action, using JavaScript's support for bitwise operators.

For more information about bitwise operator support in JavaScript, see: Bitwise Operators.