README.md

Next.js 12 with Module Federation

Module Federation in Next.js depends on @module-federation/nextjs-mf

NOTE: There seems to be a problem with css-in-js sharing between federated modules. This is likely due to some internal module not being shared as a singleton. PR is welcome

Getting Started

1. run npm install @module-federation/nextjs-mf with npm 7 (yarn probably better) or install it directly in each folder/app
2. run yarn start and browse to http://localhost:3001

We are available to consult

Looking for SSR over fetch() or architecture support and designs for module federation and Next.js?

Contact me zackary.l.jackson@gmail.com or @ScriptedAlchemy on Twitter

Context

We have three next.js applications

• checkout - port 3000
• home - port 3001
• shop - port 3002

The applications utilize omnidirectional routing and pages or components are able to be federated between applications like a SPA

I am using hooks here to ensure multiple copies of react are not loaded into scope on server or client.

Sharing

Next.js does not have an async boundary. Between the entrypoint and the shared code. Read this for more context: https://github.com/sokra/slides/blob/master/content/ModuleFederationWebpack5.md

In order for webpack to figure out who shares what, an async boundary is typically needed somewhere before the module is used. Usually, we can work around async boundaries for things like react by specifying the following

https://medium.com/dev-genius/module-federation-advanced-api-inwebpack-5-0-0-beta-17-71cd4d42e534?source=friends_link&sk=70658eb0bf58dfcc5ce534cb1cd78b1f

const config = {
  shared: {
    react: {
      eager: true,
      singleton: true,
    },
  },
};

However, in the case of Next.js - you need to use @module-federation/nextjs-mf

Reference Points

I do have some helpful examples floating around, hopefully these will be of use.

Next.js specific:

• module-federation#155
• https://github.com/module-federation/module-federation-examples/blob/master/nextjs-sidecar/

SSR Specific:

• https://github.com/module-federation/module-federation-examples/tree/master/server-side-rendering

Useful files in the SSR build.

• https://github.com/module-federation/module-federation-examples/blob/master/server-side-rendering/website1/build/webpack.config.js/server.base.js
• https://github.com/module-federation/module-federation-examples/blob/master/server-side-rendering/website1/build/webpack.config.js/client.base.js
• Entrypoint - https://github.com/module-federation/module-federation-examples/blob/master/server-side-rendering/website1/server/index.js
• Async import middleware - https://github.com/module-federation/module-federation-examples/blob/master/server-side-rendering/website1/server/server-entry.js

The async import middleware is where i keep the async boundary, this is also the only point of reference where React is import into scope.

By doing so, I can ensure that webpack has time to initialize and load anything it might need before attempting to actually require, and render the application.