What is Scalprum?

Scalprum is a tool for building dynamic frontend UIs from a variety of different sources. Thanks to Scalprum’s dynamic nature, you can pick and choose different components that you want to pull into your UI without having to worry about rebuilding your UI each time you pull in a change. Scalprum has been built with configurability in mind - you can manage different outputs all from one configuration file, without the need to fill your code with conditionals.

Scalprum is a JavaScript micro frontend framework. It leverages webpack 5 and its module federation features to create fast and scaleable micro frontend environments.

Roadmap

See our roadmap to v1 to get of a future fo Scalprum.

Getting started

Prerequisites

Ensure that you have Node.js installed.
Environment using webpack 5 to build the final output
Using React frontend library

Procedure

Demo environment setup

The following steps outline an example webpack development setup for demo purposes. You can adjust the steps to suit your own development requirements.

Create a working directory for the project:

mkdir scalprum-demo && cd scalprum-demo

Use the following command to initialise a node.

npm init

Optional: Depending on your needs, you might want to create a Git repository:

git init

Create a webpack project to set up the development dependencies:

npm i --save-dev webpack webpack-cli webpack-dev-server swc-loader

Install swc-loader so that the webpack can understand react:

npm i --save-dev swc-loader @swc/core

Generate a default webpack configuration, and enter 'y' to any options you want to include:

npx webpack init

Edit the tsconfig.json file to match the following configuration:

{
  "compilerOptions": {
    "allowSyntheticDefaultImports": true,
    "noImplicitAny": true,
    "module": "ESNext",
    "target": "ESNext",
    "allowJs": true,
    "moduleResolution": "node",
    "jsx": "react",
    "strict": true,
    "esModuleInterop": true,
    "forceConsistentCasingInFileNames": true,
    "skipLibCheck": true,
  },
  "include": ["src/**/*tsx", "src/**/*ts"]
}

Install Scalprum and its dependencies:

npm i react react-dom @scalprum/core @scalprum/react-core

Add a type definition for react:

npm i --save-dev @types/react-dom @types/react

Edit the index.html file to add the root element also to the html:

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8"/>
            <title>Webpack App</title>
    </head>
<body>
<div id="root"></div>
</body>
</html>

Edit the webpack.config.js file to match the following configuration:

// Generated using webpack-cli https://github.com/webpack/webpack-cli

const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");
const { ModuleFederationPlugin } = require('webpack').container;

const isProduction = process.env.NODE_ENV == "production";

const stylesHandler = MiniCssExtractPlugin.loader;

const config = {
  entry: "./src/index.ts",
  output: {
    path: path.resolve(__dirname, "dist"),
  },
  devServer: {
    open: true,
    host: "localhost",
  },
  plugins: [
    new HtmlWebpackPlugin({
      template: "index.html",
    }),
    new MiniCssExtractPlugin(),
    new ModuleFederationPlugin({
      name: 'shell',
      filename: isProduction ? 'shell-entry.[contenthash].js' : 'shell-entry.js',
      shared: [
        {
          react: {
            requiredVersion: '*',
            singleton: true,
          },
          'react-dom': {
            requiredVersion: '*',
            singleton: true,
          },
          '@scalprum/react-core': { singleton: true, requiredVersion: '*' },
          '@openshift/dynamic-plugin-sdk': { singleton: true, requiredVersion: '*' },
        },
      ],
    }),
  ],
  module: {
    rules: [
      {
        test: /\.(ts|tsx)$/i,
        use: {
          loader: 'swc-loader',
          options: {
            jsc: {
              parser: {
                syntax: 'typescript',
                tsx: true
              }
            }
          }
        },
        exclude: ["/node_modules/"],
      },
      {
        test: /\.css$/i,
        use: [stylesHandler, "css-loader"],
      },
      {
        test: /\.s[ac]ss$/i,
        use: [stylesHandler, "css-loader", "sass-loader"],
      },
      {
        test: /\.(eot|svg|ttf|woff|woff2|png|jpg|gif)$/i,
        type: "asset",
      },

      // Add your rules for custom modules here
      // Learn more about loaders from https://webpack.js.org/loaders/
    ],
  },
  resolve: {
    extensions: [".tsx", ".ts", ".jsx", ".js", "..."],
  },
};

module.exports = () => {
  if (isProduction) {
    config.mode = "production";
  } else {
    config.mode = "development";
  }
  return config;
};

Change the index.ts file to match the following example:

import('./bootstrap.tsx')

Create a bootstrap.tsx file with this code:

import React from 'react';
import { createRoot } from 'react-dom/client';

const App = () => {
  return (
    <div>I am an app</div>
  )
}

const domNode = document.getElementById('root');
if(domNode) {
  const root = createRoot(domNode);
  root.render(<App />)
}

If everything is set up, you can run npm run serve and view the example text that you entered in the <div> of index.tsx.

Scalprum setup

To use Scalprum, we must create a host application.

A host application is the main provider that manages module loading, routing, data sharing, and related tasks. It functions as the manager of the micro-frontend. The host application always loads first. It can be any React application as long as it has some mandatory webpack configuration.

To create a host application - a top-level application to manage the micro frontend, in the scalprum-demo/src directory, create a ScalprumRoot.tsx file, and edit to match the following configuration:

import React from 'react';
import { AppsConfig } from '@scalprum/core'
import { ScalprumProvider, ScalprumComponent } from '@scalprum/react-core'

const config: AppsConfig = {
  remoteModule: {
    name: 'remoteModule',
    manifestLocation: 'http://localhost:8003/plugin-manifest.json'
  }
}

const ScalprumRoot = () => {
  return (
    <div>
      <ScalprumProvider config={config}>
        <ScalprumComponent scope="remoteModule" module="RemoteModuleComponent" />
      </ScalprumProvider>
    </div>
  )
}

export default ScalprumRoot;

Let's take a look at what we set up in this example.

Component	Definition
`AppsConfig module`	The `AppsConfig` is a set of dynamic modules from '@scalprum/core'. This is framework-agnostic and will work as long as it is in Javascript.
`@scalprum/core` package	The `@scalprum/core` package is responsible for managing federated modules. It provides an abstraction on low-level API to make it more developer friendly alongside additional features. Behind the scenes, it uses our exposed webpack modules, `@openshift/dynamic-plugin-sdk`, to manage plugins.
`ScalprumProvider` module	The `ScalprumProvider` is the main root component. If you want to load modules, you must ensure they are enclosed in the `<ScalprumProvider />` components. `ScalprumProvider` has a mandatory `config` field. This informs `ScalprumProvider` of which remote modules are available to render. For the purpose of the demo, `const config: AppsConfig = {}`, we set up `remoteModule` to use in the next steps. The config requires a `name`, and a `manifestLocation`.
`@scalprum/react-core`	The `@scalprum/react-core` packages provide react core bindings for `@scalprum/core`.
`ScalprumComponent`	The `ScalprumComponent` is provided by the `@scalprum/react-core` packages. It requires two parameters: `scope`: the `name` that you set in the `ScalprumProvider`'s `config{}`. `module`: the actual module that you want to render. For the purposes of this demo, create `RemoteModuleComponent`.

|

Edit the index.tsx file and make the following changes:

import React from 'react';
import { createRoot } from 'react-dom/client';
import ScalprumRoot from './ScalprumRoot';

const App = () => {
  return (
    <ScalprumRoot/>
  )
}

const domNode = document.getElementById('root');
if(domNode) {
  const root = createRoot(domNode);
  root.render(<App />)
}

In the webpack.config.js file, add the moduleFederation plugin to set up the environment for plugin applications to use the context of the host applications:

// declare shared dependencies
const moduleFederationPlugin = new ModuleFederationPlugin({
  name: 'host',
  filename: 'host.[contenthash].js',
  shared: [
    {
      '@openshift/dynamic-plugin-sdk': {
        singleton: true,
        requiredVersion: '*',
      },
    },
    {
      '@scalprum/react-core': {
        singleton: true,
        requiredVersion: '*',
      },
    },
    { react: { singleton: true, requiredVersion: '*' } },
    { 'react-dom': { singleton: true, requiredVersion: '*'} },
    // any other packages you wish to share
  ],
});

Note that for demo purposes, the requiredVersion for dependencies in this example is set to *, but you can update this to a version that suits your requirements.

In the webpack.config.js file, add an entry also for the moduleFederationPlugin to the declared plugins:

   plugins: [
    new HtmlWebpackPlugin({
      template: "index.html",
    }),
    new MiniCssExtractPlugin(),
    // scalprum required plugin
    moduleFederationPlugin,
  ],

To create the remote module, in the scalprum-demo directory, create a remoteModule directory.
Install the following dependencies:

npm i --save-dev @openshift/dynamic-plugin-sdk-webpack

In the scalprum-demo/remoteModule directory, create a webpack.config.js file.
You can copy the contents of webpack.config.js file from the previous steps.
In the webpack.config.js file, remove the HtmlWebpackPlugin because it breaks dynamic modules. This is a known issue that is being actively worked on.
Remove the moduleFederationPlugin and replace with the DynamicRemotePlugin:

// declare shared dependencies

const { DynamicRemotePlugin } = require('@openshift/dynamic-plugin-sdk-webpack');

const sharedModules = {
  '@openshift/dynamic-plugin-sdk': { singleton: true },
  '@scalprum/react-core': { singleton: true },
  react: { singleton: true },
  'react-dom': { singleton: true },
};

const dynamicPlugin = new DynamicRemotePlugin({
  extensions: [],
  sharedModules,
  entryScriptfilename: 'remoteModule.[contenthash].js',
  pluginMetadata: {
    name: 'remoteModule',
    version: '1.0.0',
    exposedModules: {
      RemoteModuleComponent: './remoteModule/src/RemoteModuleComponent.tsx',
    },
    extensions: [],
  },
});

In the webpack.config.js file, also replace the moduleFederationPlugin with the dynamicPlugin plugins:

   plugins: [

    new MiniCssExtractPlugin(),
    // scalprum required plugin
    dynamicPlugin
    ,
  ],

In the webpack.config.js file, also add a publicPath:

const config = {
    entry: "./src/index.tsx",
    output: {
    path: path.resolve(_dirname, "dist"),
    publicPath:'http://localhost:8003'
    },
devServer: {
    open: true,
    host: "localhost",
},

In your scalprum-demo/remoteModule directory, create a src directory.
In your scalprum-demo/remoteModule/src directory, create an index.tsx file.
In your scalprum-demo/remoteModule/src directory, create a RemoteModuleComponent.tsx file and add the following:

import React from 'react';

const RemoteModuleComponent = () => {
  return (
    <div>
    I am a remote module component;
    </div>
  )
}

export default RemoteModuleComponent;

In the scalprum-demo/package.json file, add the following entry and point to remoteModule/webpack.config.js as your configuration file:

"build:plugin":"webpack --mode=production --node-env=production -c remoteModule/webpack.config.js"

To test if everything is set up correctly, enter the following command:

npm run build:plugin

Normally, your modules would be served via your own content delivery network, but for demo purposes, you can serve it locally from the dist directory that is created when you run npm run build:plugin.

cd scalprum-demo/remoteModule/dist/ && npx http serve . -p 8003

If this action completes without error, you can view your plugin manifest at http://localhost:8003/. You can also run the host application via npm run serve and check if the dynamic plugin was loaded correctly in the UI.

Reference information

dependencies

npm i @openshift/dynamic-plugin-sdk @scalprum/core @scalprum/react-core

Webpack config

TODO: Create host webpack plugin or extensible default webpack config

// webpack.config.js

// require module federation plugin
const { ModuleFederationPlugin } = require('webpack').container;

// declare shared dependencies
const moduleFederationPlugin = new ModuleFederationPlugin({
  name: 'host',
  filename: 'host.[contenthash].js',
  shared: [{
    // These packages has to be shared and has to be marked as singleton!
    { '@openshift/dynamic-plugin-sdk', { singleton: true, }}
    { '@scalprum/react-core': { singleton: true, } },
    { react: { singleton: true, } },
    { 'react-dom': { singleton: true } },
    // any other packages you wish to share
  }]
})

module.exports = {
  // regular react webpack config
  plugins: [moduleFederationPlugin, ... /** other plugins you need */]
}

The host application requires an extra module federation plugin to be compatible with scalprum packages.

The following modules have to be shared and marked as singletons:

@scalprum/react-core
react
react-dom

If your application requires additional shared/singleton packages (eg. react-router-dom) they can be added to the plugin configuration.

ScalprumProvider

The ScalprumProvider is a root React node that propagates necessary context to its children. It requires a configuration object that is referenced when a module is loaded.

import App from './App'

const config = {
  testModuleOne: {
    name: 'testModuleOne', // module name
    manifestLocation: '/path/to/manifest/file.json' // metadata file with module entry script location and other information
  },
  testModuleTwo: {
    name: 'testModuleTwo',
    manifestLocation: ...
  }
}

const HostRoot = () => {
  return (
    <ScalprumProvider
      api={{
        /** Custom object */
      }}
      config={config}
    >
      <App />
    </ScalprumProvider>
  )
}

export default HostRoot

config

The config prop contains is a module registry. The config data is used to load and initialize modules at runtime.

type Config = {
  [name: string]: {
    name: string;
    manifestLocation: string;
  }
}

api

The api prop is an object that is available to all provider children nodes via useScalprum hook. It is a good place to store your global context (user, auth API, etc...).

const HostRoot = () => {
  return (
    <ScalprumProvider
      api={{
        user: {
          name: 'John Doe',
          email: 'johndoe@email.com'
        }
      }}
      config={config}
    >
      <App />
    </ScalprumProvider>
  )
}

import { useScalprum } from '@scalprum/react-core'

const Plugin = () => {
  const { api: { user } } = useScalprum()
  return (
    <div>
      <h2>Hello {user.name}</h2>
    </div>
  )
}

ScalprumComponent

The ScalprumComponent is a react binding that directly renders a module. The referenced module has to be a React component. The module also has to be present in the ScalprumProvider config.

import { ScalprumComponent } from '@scalprum/react-core';

const RemotelyLoadedComponent = () => {

  const anyProps = {
    foo: 'bar'
  }

  return (
    <ScalprumComponent
      scope="testModuleOne"
      module=" "
      // any non scalprum props will be passed to the actual component
      {...anyProps} 
    />
  );
}

importName

The importName prop is a string that is used to reference the module. It is a name of the exported component from the module. Should be used if other than default export is required.

// Remote module definition
export const NamedComponent = () => {
  return (
    <div>
      <h2>Named component</h2>
    </div>
  )
}

// Consumer
<ScalprumComponent {...props} importName="NamedComponent">

One module can have multiple exports.

fallback

Similar to React.Suspense. This component will be loaded before the module is ready.

<ScalprumComponent {...props} fallback={<Spinner />}>

ErrorComponent

A node that is rendered if a module encountered a runtime error or failed to load.

// error type cannot be strict and depends on type of error and on application
const ErrorComponent = ({ error, errorInfo }) => {
  useEffect(() => {
    // handle the error (report to logging service)
  }, [])
  return (
    <div>
      <h2>Error rendering component</h2>
    </div>
  )
}


<ScalprumComponent {...props} ErrorComponent={<ErrorComponent />}>

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What is Scalprum?

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Reference information

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What is Scalprum?

Roadmap

Getting started

Prerequisites

Procedure

Demo environment setup

Scalprum setup

Reference information

Webpack config

ScalprumProvider

ScalprumComponent