โมดูลซิงเกิลตันและการจัดการเวอร์ชัน

In Micro Frontend architectures, a singleton module is a piece of code or a library that should only ever exist as a single instance across your entire application, even if multiple Micro Frontends try to load it.

Think of it as a unique resource that all parts of your system need to share consistently.

• Ensures a single source of truth.
• Prevents conflicting states or behaviors.

Imagine multiple Micro Frontends (MFEs) all loading their own copy of a UI library like React, or a state management library like Redux.

Without singletons, you could end up with:

• Multiple instances of React Context, breaking component communication.
• Separate Redux stores, leading to inconsistent application state.
• Increased bundle size due to duplicate code.

Singletons solve these issues by guaranteeing a unified dependency.

Module Federation makes it easy to declare shared modules as singletons using the singleton: true option in your Webpack configuration.

When this is set, Webpack ensures that only one version of the specified module is loaded and used by all federated applications (hosts and remotes) at runtime.

Here's how you'd configure a shared module, like react, to be a singleton in your webpack.config.js:

Beyond ensuring a single *instance* (singleton), you also need to manage which *version* of a shared module gets loaded.

What if one MFE needs React v17 and another needs React v18? Module Federation has mechanisms to handle these version conflicts and ensure compatibility or gracefully fail.

The requiredVersion option in the shared configuration allows you to specify the semantic version (semver) range that your application expects for a shared module.

Webpack will try to find a compatible version among the host and remote applications. If a compatible version is found, it's used. If not, it might load a fallback or throw an error, depending on other settings.

Here's how you might define a requiredVersion for a shared library:

While requiredVersion guides version selection, strictVersion: true enforces it rigorously.

If strictVersion: true is enabled and a remote module requests a version that is incompatible with the host's requiredVersion (or the version already loaded), Module Federation will throw an error and prevent the application from loading. This prevents unexpected behavior from version mismatches.

Combining singleton, requiredVersion, and strictVersion for critical dependencies:

To effectively manage singleton modules and versioning:

• Use Semantic Versioning (SemVer): Adhere to major.minor.patch for all shared modules.
• Communicate: Ensure teams are aware of shared module updates and version requirements.
• Test Compatibility: Regularly test your federated applications to ensure shared modules work across all remotes and hosts.
• Be Strategic: Not all shared modules need to be singletons or have strict versioning. Apply these settings thoughtfully based on the module's criticality.

You've now learned about singleton modules and versioning in Module Federation!

• Singleton modules ensure only one instance of a shared dependency exists across your federated application, crucial for stateful libraries.
• The requiredVersion and strictVersion options help manage compatibility and prevent issues arising from conflicting module versions.

These techniques are vital for building robust and predictable Micro Frontend applications.