Configuration Parameters

Input

Output

Creating a JavaScript Extension

1. Create an extension of the JavaScript operator and add the desired input and output ports.
2. Add your JavaScript snippet as an inline "script" parameter in the extension configuration or put the code into a separate file and use the prefix "file://" to specify the file name.

Basic Example

var counter = 0

$.setPortCallback("input",onInput)

function onInput(ctx,s) {
    counter++
    $.output(counter)
}

Generators

Generators are functions that are executed before the event processing loop starts.

var counter = 0

$.addGenerator(gen)
$.addGenerator(gen)

function gen(ctx) {
    for (var i = 0; i < 3; i++ ) {
      $.output(counter)
      counter++
    }
}

This example produces the values 0,1,2,3,4,5 on the output port "output".

Timers

This example produces the values 0,1,2,3,4,5 on the output port "output".

var counter = 0

$.addTimer("1s",t1)

function t1(ctx) {
  $.output(counter)
  counter++
}

This example produces the values 0,1,2... on port "output" until graph shutdown.

Shutdown Handlers

This example produces the values 0,1,2... on port "output" until graph shutdown.

var counter = 0

$.setPortCallback("input",onInput)

function onInput(ctx,s) {
    counter++
}

function shutdown(ctx) {
    $.output(counter)
}

$.addShutdownHandler(shutdown)
$.addShutdownHandler(shutdown)

This example produces values 7,7 if 7 values have been provided on the "input" port.

Configuration API

Configuration API provides the ability to read the configuration provided via a graph description.

function gen(ctx) {
  $.str($.config.getString("str"))
  $.int($.config.getInt("int"))
  $.bool(""+$.config.getBool("bool"))
  $.msg({Attributes: $.config.getObject("obj")})
  $.msg({Attributes: $.config.asObject()})
}
$.addGenerator(gen)

This example reads the configuration of the operator and provides the given values on the output ports.

Error Handling

The fail function provides the ability to terminate a processing loop in case of an internal error.

var counter = 0

$.setPortCallback("input",onInput)

function onInput(ctx,s) {
    counter++
    if (counter > 1 ) {
      $.fail("Failure in counter")
    }
    $.output(counter)
}

This example terminates the loop while processing the second input on "input" port.

Message Response Handling

The sendResponse function provides the ability to send either a response or error message to the request-response initiating operator. This function is only valid if the incoming data is of type message and it contains the response callback as part of a request-response message exchange.

var counter = 0

function onInput(ctx,s) {
    counter++
    if (counter < 100) {
        var msg = {};
        msg.Body = "pong " + counter;
        $.sendResponse(s, msg, null);
    } else {
        $.sendResponse(s, null, Error("Usage limit reached " + counter));
    }
}

This example sends a response or error depending on the current counter value.

Send Message to Logging App

Another optional parameters are user, messageCode, and details.

The function awaits the logging API call execution, returning a message if the log message was successfully sent to the logging app.

$.log("message to log", $.logSeverity.INFO, "", "10003", "this is a detailed message to the log message");

This example sends a message with INFO severity to the logging app, an empty value for the user parameter and a value for the messageCode and details parameters.