Script Processor

The script processor executes Javascript code to process an event. The processor uses a pure Go implementation of ECMAScript 5.1 and has no external dependencies. This can be useful in situations where one of the other processors doesn’t provide the functionality you need to filter events.

The processor can be configured by embedding Javascript in your configuration file or by pointing the processor at external files.

- script:
    lang: javascript
    source: >
      function process(event) {
          event.Tag("js");
      }

This example loads filter.js from disk:

- script:
    lang: javascript
    file: ${path.config}/filter.js

Parameters can be passed to the script by adding params to the config. This allows for a script to be made reusable. When using params the code must define a register(params) function to receive the parameters.

- script:
    lang: javascript
    tag: my_filter
    params:
      threshold: 15
    source: >
      var params = {threshold: 42};
      function register(scriptParams) {
          params = scriptParams;
      }
      function process(event) {
          if (event.Get("severity") < params.threshold) {
              event.Cancel();
          }
      }

If the script defines a test() function, it will be invoked when the processor is loaded. Any exceptions thrown will cause the processor to fail to load. This can be used to make assertions about the behavior of the script.

function process(event) {
    if (event.Get("event.code") === 1102) {
        event.Put("event.action", "cleared");
    }
    return event;
}

function test() {
    var event = process(new Event({event: {code: 1102}}));
    if (event.Get("event.action") !== "cleared") {
        throw "expected event.action === cleared";
    }
}

The Event object passed to the process method has the following API.