ember-cli-fastboot

Ember FastBoot

An Ember CLI addon that allows you to render and serve Ember.js apps on the server. Using FastBoot, you can serve rendered HTML to browsers and other clients without requiring them to download JavaScript assets.

Currently, the set of Ember applications supported is extremely limited. As we fix more issues, we expect that set to grow rapidly. See Known Limitations below for a full-list.

The bottom line is that you should not (yet) expect to install this add-on in your production app and have FastBoot work.

Installation

FastBoot requires Ember 2.3 or higher.

From within your Ember CLI application, run the following command:

ember install ember-cli-fastboot

Running

• ember fastboot --serve-assets
• Visit your app at http://localhost:3000.

You may be shocked to learn that minified code runs faster in Node than non-minified code, so you will probably want to run the production environment build for anything "serious."

ember fastboot --environment production

You can also specify the port (default is 3000):

ember fastboot --port 8088

See ember help fastboot for more.

Using Node/npm Dependencies

Whitelisting Packages

When your app is running in FastBoot, it may need to use Node packages to replace features that are available only in the browser.

For security reasons, your Ember app running in FastBoot can only access packages that you have explicitly whitelisted.

To allow your app to require a package, add it to the fastbootDependencies array in your app's package.json:

{
  "name": "my-sweet-app",
  "version": "0.4.2",
  "devDependencies": {
    // ...
  },
  "dependencies": {
    // ...
  },
  "fastbootDependencies": [
    'rsvp',
    'path'
  ]
}

The fastbootDependencies in the above example means the only node modules your Ember app can use are rsvp and path.

If the package you are using is not built-in to Node, you must also specify the package and a version in the package.json dependencies hash. Built-in modules (path, fs, etc.) only need to be added to fastbootDependencies.

Using Dependencies

From your Ember.js app, you can run FastBoot.require() to require a package. This is identical to the CommonJS require except it checks all requests against the whitelist first.

let path = FastBoot.require('path');
let filePath = path.join('tmp', session.getID());

If you attempt to require a package that is not in the whitelist, FastBoot will raise an exception.

Note that the FastBoot global is only available when running in FastBoot mode. You should either guard against its presence or only use it in FastBoot-only initializers.

Known Limitations

While FastBoot is under active development, there are several major restrictions you should be aware of. Only the most brave should even consider deploying this to production.

No didInsertElement

Since didInsertElement hooks are designed to let your component directly manipulate the DOM, and that doesn't make sense on the server where there is no DOM, we do not invoke either didInsertElement nor willInsertElement hooks.

No jQuery

Running most of jQuery requires a full DOM. Most of jQuery will just not be supported when running in FastBoot mode. One exception is network code for fetching models, which we intended to support, but doesn't work at present.

No JavaScript Served

Right now, this is only useful for creating an HTML representation of your app at a particular route and serving it statically. Eventually, we will support also serving the JavaScript payload, which can takeover once it has finished loading and making the app fully interactive.

In the meantime, this is probably only useful for cURL or search crawlers.

Troubleshooting

Because your app is now running in Node.js, not the browser, you'll need a new set of tools to diagnose problems when things go wrong. Here are some tips and tricks we use for debugging our own apps.

Verbose Logging

Enable verbose logging by running the FastBoot server with the following environment variables set:

DEBUG=ember-cli-fastboot:* ember fastboot

PRs adding or improving logging facilities are very welcome.

Developer Tools

You can get a debugging environment similar to the Chrome developer tools running with a FastBoot app, although it's not (yet) as easy as in the browser.

First, install the Node Inspector:

npm install node-inspector -g

Make sure you install a recent release; in our experience, older versions will segfault when used in conjunction with Contextify, which FastBoot uses for sandboxing.

Next, start the inspector server. We found the experience too slow to be usable until we discovered the --no-preload flag, which waits to fetch the source code for a given file until it's actually needed.

node-inspector --no-preload

Once the debug server is running, you'll want to start up the FastBoot server with Node in debug mode. One thing about debug mode: it makes everything much slower. Since the ember fastboot command does a full build when launched, this becomes agonizingly slow in debug mode.

Avoid the slowness by manually running the build in normal mode, then running FastBoot in debug mode without doing a build:

ember build && node --debug-brk ./node_modules/.bin/ember fastboot --no-build

This does a full rebuild and then starts the FastBoot server in debug mode. Note that the --debug-brk flag will cause your app to start paused to give you a chance to open the debugger.

Once you see the output debugger listening on port 5858, visit http://127.0.0.1:8080/debug?port=5858 in your browser. Once it loads, click the "Resume script execution" button (it has a ▶︎ icon) to let FastBoot continue loading.

Assuming your app loads without an exception, after a few seconds you will see a message that FastBoot is listening on port 3000. Once you see that, you can open a connection; any exceptions should be logged in the console, and you can use the tools you'd expect such as console.log, debugger statements, etc.

Tests

Run the automated tests by running npm test.

Note that the integration tests create new Ember applications via ember new and thus have to run an npm install, which can take several minutes, particularly on slow connections.

To speed up test runs you can run npm run test:precook to "precook" a node_modules directory that will be reused across test runs.

Debugging Integration Tests

Run the tests with the DEBUG environment variable set to fastboot-test to see verbose debugging output.

DEBUG=fastboot-test npm test