jeffamcgee/ember-prerender

Make your Ember.js web apps crawlable by rendering static HTML on the server.

Ember Prerender

This project allows Ember.js (and likely other) web applications to be prerendered on the server using Node.js and either PhantomJS or JSDOM based on your preference.

The goal of the project is to couple server-side rendering more closely with a specific web app framework. By utilizing a long-lived instance of an app rather than reloading it on every request, rendering times can be reduced.

The concept and plugin code is based loosely off of the Prerender Service by Todd Hooper.

Usage

Install ember-prerender:

$ sudo npm install -g zipfworks/ember-prerender

Copy or edit the default configuration file (in /config/) to match your app's environment.

Run the service with the path to your configuration file:

$ ember-prerender config/default.js [optional process num]

If you're invoking node directly:

$ export CONFIG="./config/default.js"
$ export PROCESS_NUM=0
$ node server.js

Ember Prerender Event

In order for ember-prerender to know that your pages are fully rendered, your application must emit the prerenderReady event whenever each of your routes finishes rendering their templates.

Example configuration (CoffeeScript):

Add to: app/initialize.coffee

# Prerender event
prerenderEvent = document.createEvent('Event')
prerenderEvent.initEvent('prerenderReady', true, true)
App.prerenderReady = ->
  console.log('PRERENDER READY')
  document.dispatchEvent(prerenderEvent)

In your routes (as of Ember 1.4):

  # Promise hook for when a page has loaded, can be overridden in subclasses
  willComplete: -> Em.RSVP.resolve()

  actions:
    didTransition: ->
      promises = []
      for handler in @router.router.currentHandlerInfos
        if handler.handler.willComplete
          promises.push handler.handler.willComplete()
      Ember.RSVP.all(promises).then App.prerenderReady

Instead of adding this to each of your routes, you can extend Ember.Route to create a base route or use Ember.Route.reopen to change the default behavior.

Depending on your app, you may need to postpone firing the prerenderReady event by overriding willTransition. You can do so by returning a deferred promise and resolving it after the other parts of the page have loaded.

To detect whether your app is being loaded in a browser or through prerender, you can check the window.isPrerender variable which is set to true by ember-prerender.

Reloading

If your web application changes, you can send a SIGUSR2 signal to the master prerender process to cause the page to be reloaded.

Supervisor

You may use supervisord to start, stop, restart, and monitor ember-prerender. The following is an example configuration file which should be placed in /etc/supervisor/conf.d/:

[program:prerender-yourappname]
command = ember-prerender /mnt/ebs1/www/yourappname/conf/prerender.js %(process_num)d
directory = /mnt/ebs1/www/yourappname
user = yourappname
autostart = true
autorestart = true
stopasgroup = true
stdout_logfile = /mnt/ebs1/www/yourappname/logs/prerender.log
stderr_logfile = /mnt/ebs1/www/yourappname/logs/prerender.error.log
process_name = %(program_name)s_%(process_num)02d
numprocs = 1

Web Server Setup

Once Ember Prerender is working with your project, you'll probably want to enable prerendering for certain user agents (e.g. web crawlers) while serving Javascript for compatible browsers. One way to do this is by setting up Nginx as a reverse proxy (below).

Nginx Reverse Proxy Setup

Example configuration (you can add additional instances to the upstream backend:

upstream prerender-yourappname-backend {
  #ip_hash;
  server localhost:3000;
  #server localhost:3001;
  #server localhost:3002;
  #server localhost:3003;
}

server {
  listen 80;
  listen [::]:80;
  server_name yourserver.com;
 
  root /path/to/your/htdocs;
 
  error_page 404 /404.html
  index index.html;
 
  location ~ /\. {
    deny all;
  }
 
  location / {
    try_files $uri @prerender;
  }
 
  location @prerender {
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    #proxy_intercept_errors on;
    proxy_next_upstream error timeout;
 
    set $prerender 0;
    if ($http_user_agent ~* "googlebot|yahoo|bingbot|baiduspider|yandex|yeti|yodaobot|gigabot|ia_archiver|facebookexternalhit|twitterbot|developers\.google\.com") {
      set $prerender 1;
    }
    if ($args ~ "_escaped_fragment_|prerender=1") {
      set $prerender 1;
    }
    if ($http_user_agent ~ "Prerender") {
      set $prerender 0;
    }

    if ($prerender = 1) {
      proxy_pass http://prerender-yourappname-backend;
    }
    if ($prerender = 0) {
      rewrite .* /index.html break;
    }
  }
}

License

The MIT License (MIT)

Copyright (c) 2013-2014 ZipfWorks Inc

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.