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CourseUp - Backend Services

The CourseUp application backend REST API exists as a Express application deployed on Google Cloud Platform's Cloud Functions service.

Development

Setup

Pre-requisites

In order to develop this application you will need to setup the development dependencies. It is assumed that you have:

  • Node.js 12
    • We recommend using a Node version manager available on your platform like nvm.
  • Java Runtime Environment
    • This is required to run some of the emulators as part of Firebase Tools
  • Using a *NIX compatible terminal like Git-Bash on Windows or literally anything else on Linux, macOS etc.
    • just don't use Powershell or the default Windows command prompt

Install

  1. Install Firebase Tools using npm install -g firebase-tools.
    • This will install Firebase tools globally under your current Node/npm version.
  2. Install Node dependencies using npm ci
    • Note: Avoid using npm install unless you are install/updating a dependency.

Once you're done that, you should be good to go!

Developing

Once your development environment is setup, you will be able to use the following npm scripts configured. Both must be running concurrently, so you will need to open two terminals in this directory.

Develop

  • This will start the Express application and tsoa route generator. It will rebuild the app when files change, making development quite fast and enjoyable. 
    npm run dev
  • This will start a local instance of the database allowing you to develop and test locally without modifying our production database. By default, the database will be seeded with courses from the Fall 2021 semester. 
    npm run db:start

Architecture

Since we utilize Cloud Functions to run a Express app, it is faster and easier to run the Express app through normal means rather than starting it with firebase emulators:start --only functions.

You can start the Express application and tsoa route generator with a single command using npm run dev. This will also rebuild the app when files change, making development quite fast and enjoyable.

tsoa

tsoa helps create "OpenAPI-compliant REST APIs using TypeScript and Node". As part of that process, tsoa generates Express routes from files that match *.controller.ts. This means that when a change is made to a controller, the tsoa generator must run. Developers can manually invoke the generator with npx tsoa routes.

Firebase

Since this Express app is meant to be utilized in a Firebase/Cloud Functions environment, it is important to test your changes inside the Firebase emulator prior to deployment to confirm there are no environment specific issues. While the development environment tries to address these issues, you may still run into some.

To test your changes for cloud functions within a Firebase context:

  1. Build the application with npm run build.
  2. Start the emulator with firebase emulators:start --only functions.
    • If you wish you start the entire application (including the frontend), omit --only functions.

Architecture

In this section, the architecture and structure of the application code is explained. Please similarize yourself with the basic of the model-view-controller software design pattern.

Service

Since "service" is not mentioned in most MVC type systems. we briefly explain the purpose of them.

We utilize the concept of a "service" in this application to faciliate any logic that doesn't fit in the model or controller. Since the controller faciliates how the REST API behaves such as the route and caching behaviour and the model facilitates the data we're handling, any logic that is required to accomplish what the controller needs etc. should live in the service file. This might include tasks of fetching data from a database and what not.