PeerTube/support/doc/server/code.md

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# Server code documentation
The server is a web server developed with [NodeJS](https://nodejs.org)/[Express](http://expressjs.com).
## Technologies
* [NodeJS](https://nodejs.org) -> Language
* [MongoDB](https://www.mongodb.com/) -> Database
* [Express](http://expressjs.com) -> Web server framework
* [Mongoose](http://mongoosejs.com/) -> MongoDB object modeling
* [WebTorrent](https://webtorrent.io/) -> BitTorrent over WebRTC
* [Electron](http://electron.atom.io/) -> To make WebRTC inside NodeJS
* [Mocha](https://mochajs.org/) -> Test framework
## Files
The server main file is [server.js](https://github.com/Chocobozzz/PeerTube/blob/master/server.js).
The server modules description are in the [package.json](https://github.com/Chocobozzz/PeerTube/blob/master/package.json) at the project root.
All other server files are in the [server](https://github.com/Chocobozzz/PeerTube/tree/master/server) directory:
server.js -> app initilization, main routes configuration (static routes...)
config -> server YAML configurations (for tests, production...)
scripts -> Scripts files for npm run
server
|__ controllers -> API routes/controllers files
|__ helpers -> functions used by different part of the project (logger, utils...)
|__ initializers -> functions used at the server startup (installer, database, constants...)
|__ lib -> library function (WebTorrent, OAuth2, friends logic...)
|__ middlewares -> middlewares for controllers (requests validators, requests pagination...)
|__ models -> Mongoose models for each MongoDB collection (videos, users, pods...)
|__ tests -> API tests and real world simulations (to test the decentralized feature...)
## Conventions
Uses [JavaScript Standard Style](http://standardjs.com/).
## Developing
* Install [the dependencies](https://github.com/Chocobozzz/PeerTube#dependencies)
* Run `npm install` at the root directory to install all the dependencies
* Run MongoDB
* Run `npm run dev` to compile the client and automatically run the server. If the client files are already compiled you can simply run `NODE_ENV=test node server`
The `NODE_ENV=test` is set to speed up communications between pods (see [constants.js](https://github.com/Chocobozzz/PeerTube/blob/master/server/initializers/constants.js#L71)).
`npm run help` gives you all available commands.
If you want to test the decentralization feature, you can easily run 3 pods by running `npm run play`. The pods password are `test1`, `test2` and `test3`.
## Architecture
The server is composed by:
* a REST API
* a WebTorrent Tracker
* A separate Electron process
The seperate Electron process has the goal to seed videos through WebRTC because WebRTC directly in NodeJS is not usable for now.
![Architecture scheme](https://github.com/Chocobozzz/PeerTube/blob/master/support/doc/server/upload-video.png)
When a user uploads a video, the rest API asks the Electron process to seed it (communicate with IPC) and then adds it to its Mongo database.
If a user wants to watch the video, the tracker will indicate all other users that are watching the video + the Electron process.
## Newcomers
The server entrypoint is [server.js](https://github.com/Chocobozzz/PeerTube/blob/master/server.js). You can begin to look at this file.
Then you can try to understand the [controllers](https://github.com/Chocobozzz/PeerTube/tree/master/server/controllers): they are the entrypoint of each API request.