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This document has been moved to https://github.com/edx/edx-developer-docs/blob/5191e800bf16cf42f25c58c58f983bdaf7f9305d/docs/micro-frontends-in-open-edx.rst

The purpose of this document is to provide an overview of how micro-frontend applications (MFEs) are developed, configured, and deployed with the Open edX ecosystem. Open edX MFEs are small React applications that can be built and deployed independently.

MFEs are static site generators. They are supplied configuration, then run to build HTML, CSS, and Javascript. The static assets are then ready then be moved to a location and served to the user.

All MFEs offer the following commands:

npm install (install dependencies)
npm start (development server)
npm run lint
npm run test
npm run build (build static output)

Use of Environment Variables for App Config

Open edX MFEs expect a number of process environment variables (Accessible in node via process.env) in order to properly configure authentication, routing to other parts of the system, etc. Each MFE has .env, .env.development, and .env.test files that are consumed by the MFE. The production .env file contains only null values – the build process should supply them via the command line prior to npm run build.

Example .env.development:

NODE_ENV='development'

PORT=1995

ACCESS_TOKEN_COOKIE_NAME='edx-jwt-cookie-header-payload'

BASE_URL='localhost:1995'

CREDENTIALS_BASE_URL='http://localhost:18150'

CSRF_COOKIE_NAME='csrftoken'

CSRF_TOKEN_API_PATH='/csrf/api/v1/token'

ECOMMERCE_BASE_URL='http://localhost:18130'

LANGUAGE_PREFERENCE_COOKIE_NAME='openedx-language-preference'

LMS_BASE_URL='http://localhost:18000'

LOGIN_URL='http://localhost:18000/login'

LOGOUT_URL='http://localhost:18000/login'

MARKETING_SITE_BASE_URL='http://localhost:18000'

ORDER_HISTORY_URL='localhost:1996/orders'

REFRESH_ACCESS_TOKEN_ENDPOINT='http://localhost:18000/login_refresh'

SEGMENT_KEY=null

SITE_NAME='edX'

USER_INFO_COOKIE_NAME='edx-user-info'

Overriding Brand Specific Elements

MFEs contain Open edX branded headers, footers and style. To build a MFE to reflect the brand of the particular Open edX instance some npm dependencies are designed to be overridden. Overriding packages must expose the same interface as the dependencies they are overriding.

Example: for edx.org the Open edX @edx/frontend-component-header is overridden with @edx/frontend-component-header-edx using npm aliases (introduced in npm version 6.9.0). Example syntax below:

# npm install <package-name>@<type>:<branded-package> # npm package npm install @edx/frontend-component-header@npm:@edx/frontend-component-header-edx@latest # git repository npm install @edx/frontend-component-header@git:https://github.com/edx/frontend-component-header-edx.git # local folder npm install @edx/frontend-component-header@file:../path/to/local/module

A the list overridable packages is being developed. Currently only @edx/frontend-component-header and @edx/frontend-component-footer are designed to be overridden. See those repositories for the interfaces they expose.

Deployment

Note: This section is edX specific and depends upon automation setup in GoCD. A similar, more manual process will need to be defined for Open edX installations.

edX MFEs are deployed automatically upon updates to the master branch in Github. GoCD collects three materials: the MFE source code, .yml configuration, and tubular pipeline scripts.

.yml configuration contains:

APP_CONFIG
NPM_OVERRIDES
S3_BUCKET_NAME

Relevant tubular scripts:

The tubular pipeline scripts perform a routine like below:

Parse .yml configuration
Install requirements in the MFE source via npm install
Check for NPM_OVERRIDES and install them via npm install @edx/pkg@npm:custom-pkg
Collect APP_CONFIG and transform it into command line form (NODE_ENV=development BASE_URL=open.edx.org)
Build the static output with the APP_CONFIG: NODE_ENV=development BASE_URL=open.edx.org npm run build
Deploy static output to s3 using S3_BUCKET_NAME

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