fastboot-app-server

Ember FastBoot App Server

The FastBoot App Server is an application server for hosting Ember FastBoot apps. It manages downloading the Ember app, starting multiple HTTP server processes, and detecting when new versions of the application have been deployed.

FastBoot allows Ember apps to be rendered on the server, to support things like search crawlers and clients without JavaScript. For more information about FastBoot, see FastBoot website.

Extensibility

The App Server is designed to be flexible and extensible enough to run in whatever environment you want to use to host FastBoot apps. In particular, you can provide a custom:

• Downloader, to control how app builds gets downloaded
• Notifier, to control how new versions of the build are detected
• HTTP Server, to use whatever stack you prefer for serving HTTP requests in Node.js

Requirements

FastBoot App Server requires Node.js v4.2 or later.

Quick Start

Put the following in a server.js file:

const FastBootAppServer = require('fastboot-app-server');

let server = new FastBootAppServer({
  distPath: 'dist'
});

server.start();

Configure distPath to point to the dist directory you upload to your server. (See Application Builds below.)

Run the server file:

$ PORT=8000 node server.js

This will start an HTTP server on port 8000. To stop the server, type Ctrl-C.

Application Builds

When you build an Ember.js app via ember build, it will build the app for production and, by default, put the resulting files in your application's dist directory.

Clustering

Because Node.js is single-threaded, you must run multiple processes to take advantage of multi-core systems. FastBoot App Server takes advantage of Node's clustering support out of the box, automatically spawning one worker HTTP server per core.

The app server will automatically spawn a new worker if one dies while handling a request. When a new application deploy is detected, workers will automatically reload with the newest version.

Downloaders

You can point the app server at a static path that you manage, but that means taking responsibility for uploading builds to each server whenever you want to deploy a new version.

Instead, you can provide the app server with a downloader, an adapter that knows how to download the current version of your application.

For example, to use the S3 downloader that downloads a zip file from AWS S3:

const S3Downloader = require('fastboot-s3-downloader');
const FastBootAppServer = require('fastboot-app-server');

let downloader = new S3Downloader({
  bucket: 'S3_BUCKET',
  key: 'S3_KEY'
});

let server = new FastBootAppServer({
  downloader: downloader
});

server.start();

Available Downloaders

• fastboot-s3-downloader

Writing a Downloader

To write your own downloader, construct an object that conforms to the following interface:

download()

Returns a promise that resolves to the path to the downloaded dist directory (which does not have to be named dist).

Note that download() may be called more than once in the lifetime of an application, if a new version is deployed. Make sure your downloader cleans up after itself to avoid running out of disk space.

Notifiers

Once the FastBoot App Server is up and running, it will happily chug away until the server dies or it reaches the inevitable heat death of the universe. Before that happens, presumably, you may want to deploy a new version of your application.

Notifiers are responsible for detecting when a new version of an app has been deployed and reloading the app server.

For example, here's how to use the S3 notifier, which polls the last modified date of a file on S3 to detect new versions:

const S3Notifier = require('fastboot-s3-notifier');
const FastBootAppServer = require('fastboot-app-server');

let notifier = new S3Notifier({
  bucket: S3_BUCKET,
  key: S3_KEY
});

let server = new FastBootAppServer({
  notifier: notifier
});

server.start();

Available Notifiers

• fastboot-s3-notifier

Writing a Notifier

To write your own notifier, construct an object that conforms to the following interface:

subscribe(notify)

The subscribe() method ony our notifier is passed a notify function. If you detect that a new version of your app has been deployed (whether via polling or a push notification), call this function to trigger a reload.