KO with Dependencies

Many of the functions developed for Knowledge Objects are simple and require no external libraries or files. However the use of these libraries and files can simplify design, increase maintainability and create a better solution.

The js-bundled object (opens new window) is an object that uses npm to bundle dependencies into a single javascript file that can run in the V8 engine.

Currently the KGrid Activator uses the Graal V8 (opens new window) JavaScript engine for execution of JavaScript Objects. V8 is compatible with the ECMAScript 2020 specification (opens new window) but doesn't support external dependencies without bundling your function using Webpack (opens new window) and Babel (opens new window). The use of webpack and babel allows the function to be transpiled into a graal V8 compliant code artifact.

Create bundled KO

To create a new KO from the template of bundled KO, run the KGrid CLI command and select the template type of bundled:

 kgrid create myko

Comparing with the project created as a simple KO in the developer's guide, you will notice some additional files webpack.config.js and package.json in the created KO folder. These files will configure the webpack tool to build the source files into a JAVASCRIPT bundle, ready for KGrid activator.

Looking in to the folder named /src, you will find a few more files in addition to index.js.

cvdscore.js is a Javascript file containing the core function of SCORE computation.

beta.json and coefficients.json are the data files containing coefficients for the SCORE models. They are referenced in cvdscore.js using require().

When we build the bundled KO, index.js will be the main entry for webpack.

Build bundled KO

Similar with the simple KO, the bundled KO under development is basically a Javascript project which follows the development pattern of node.js/npm.

In our example template, webpack is used to build the bundled script. We use default values for the webpack configuration wherever possible to keep it simple.

This shows the configuration file from the template.

let path = require('path');
module.exports = {

  entry: './src/index.js',

  output: {
    library: "score",
    path: path.resolve(__dirname, 'dist')
  },

  module: {
    rules: [
      {
        test: /\.m?js$/,
        exclude: /(node_modules|bower_components)/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env']
          }
        }
      }
    ]
  },
};

By default, the output.libraryTarget is set as 'var'. For bundling the KO for Graal V8 Script Engine, only 'var', 'assign' and 'this' are valid options. By default, the output file is set as 'main.js' in the folder defined in path. In the example template, it will be /dist.

WARNING

Note library name in the output element library: "score" must match the deployment description element entry: score found on the deployment specification page.

For details on customization of the webpack config, please refer to Webpack Documentation (opens new window)

To bundle the code you need to change to the ko directory and run

npm install

Once npm installs all dependencies, run

npm run build

The build process will create a file main.js in /dist directory. deployment.yaml is referring this file as the artifact for the service. Note that this object will not run in an activator if it has not been bundled.

Activate bundled KO Service

Now, the bundled KO is ready to be activated. The activation process is the same as described in the developer's guide, referring to the Kgrid Activator Documentation (opens new window).