Error Handling

Error Handling Overview

At its core, error handling is about doing one thing well inside your Module Federation project. Once you understand the pattern, you can apply it consistently across features and teams.

Good error handling pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

const ProductList = React.lazy(() =>
  import('catalog/ProductList').catch(() => ({
    default: () => <p>Catalog is temporarily unavailable</p>,
  })),
);

Always provide a fallback so a failing remote degrades gracefully instead of crashing the shell.

Error Handling 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 Error Handling example and grow it only as needed.
• Keep configuration explicit so Error Handling behaves the same in every environment.
• Name things clearly so teammates understand your Error Handling at a glance.
• Add tests around Error Handling early to lock in expected behaviour.

Module Federation Cheatsheet

Key Module Federation settings related to error handling.

How Error Handling Works in Module Federation

Error Handling 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.

Always provide a fallback so a failing remote degrades gracefully instead of crashing the shell.

• 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 Error Handling

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

Common Mistakes

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

Key Takeaways

• Error Handling is a core part of working effectively with Module Federation.
• Start small and keep error handling focused on a single responsibility.
• Apply consistent patterns so error handling scales across your project.
• Test and document error handling to keep it maintainable over time.