RxJS State Sharing

RxJS State Sharing is an important part of building production-ready Module Federation systems. This lesson explains what rxjs state sharing means, how it works, and how to apply it with practical examples you can reuse.

RxJS State Sharing Overview

RxJS State Sharing lets you structure Module Federation work so it stays readable, testable, and easy to scale. Instead of ad-hoc code, you follow a clear pattern that other developers can recognise immediately.

The key is to keep rxjs state sharing focused and predictable. Start from the minimal example here, then layer in only the complexity your feature actually needs.

const { ModuleFederationPlugin } = require('webpack').container;

module.exports = {
  plugins: [
    new ModuleFederationPlugin({
      name: 'shell',
      remotes: { catalog: 'catalog@http://localhost:3001/remoteEntry.js' },
      exposes: {},
      shared: { react: { singleton: true }, 'react-dom': { singleton: true } },
    }),
  ],
};

ModuleFederationPlugin configures which modules an app exposes, consumes, and shares.

RxJS State Sharing Example

new ModuleFederationPlugin({
  name: 'app',
  filename: 'remoteEntry.js',
  exposes: { './Widget': './src/Widget' },
  remotes: { other: 'other@http://host/remoteEntry.js' },
  shared: { react: { singleton: true } },
});

Start from a minimal RxJS State Sharing example and grow it only as needed.
Keep configuration explicit so RxJS State Sharing behaves the same in every environment.
Name things clearly so teammates understand your RxJS State Sharing at a glance.
Add tests around RxJS State Sharing early to lock in expected behaviour.

Module Federation Cheatsheet

Key Module Federation settings related to rxjs state sharing.

Option	Example	Purpose
name	`name: 'shell'`	Unique container name
filename	`filename: 'remoteEntry.js'`	Remote entry manifest
exposes	`exposes: { './X': './src/X' }`	Modules a remote shares
remotes	`remotes: { app: 'app@url' }`	Remotes a host consumes
shared	`shared: { react: { singleton: true } }`	Deduplicate libraries
lazy load	`import('remote/Module')`	Load remotes on demand
Suspense	`<Suspense fallback={...}>`	Handle async loading

How RxJS State Sharing Works in Module Federation

RxJS State Sharing builds on Module Federation's ability to load code from another independently built and deployed application at runtime. Each app can be a host, a remote, or both.

ModuleFederationPlugin configures which modules an app exposes, consumes, and shares.

Remotes expose modules through a remoteEntry.js manifest.
Hosts declare remotes and import exposed modules dynamically.
Shared dependencies are deduplicated, ideally as singletons.
Each micro frontend builds and deploys on its own schedule.

Practical Guidance for RxJS State Sharing

In production, rxjs state sharing needs careful version management and graceful failure handling. Align shared dependency versions and always render a fallback when a remote cannot load.

Concern	Recommendation
Shared versions	Use singletons with requiredVersion
Runtime errors	Wrap remotes in error boundaries and fallbacks
Deployment	Resolve remotes from a runtime manifest
Performance	Lazy-load remotes and cache remoteEntry.js

Common Mistakes

Copying rxjs state sharing snippets without understanding what each line does.
Skipping error handling and edge cases when wiring up rxjs state sharing.
Leaving rxjs state sharing untested, so regressions slip into production.
Over-engineering rxjs state sharing before you actually need the extra flexibility.

Key Takeaways

RxJS State Sharing is a core part of working effectively with Module Federation.
Start small and keep rxjs state sharing focused on a single responsibility.
Apply consistent patterns so rxjs state sharing scales across your project.
Test and document rxjs state sharing to keep it maintainable over time.

Pro Tip

When you get stuck on rxjs state sharing, reduce it to the smallest reproducible example first — most Module Federation issues become obvious once the noise is gone.