This started as a thought experiment that is growing into a viable option for realtime Rails apps without ditching the standard rails stack that we love and are so productive with for a heavy client side MVC framework.

Real-time partials with Rails. Sync lets you render partials for models that, with minimal code, update in realtime in the browser when changes occur on the server.

In practice, one simply only needs to replace:

<%= render partial: 'user_row', locals: {user: @user} %>

with:

<%= sync partial: 'user_row', resource: @user %>

Then update views realtime with a simple sync_update(@user) in the controller without any extra javascript or configuration.

In addition to real-time updates, Sync also provides:

• Realtime removal of partials from the DOM when the sync'd model is destroyed in the controller via sync_destroy(@user)
• Realtime appending of newly created model's on scoped channels
• JavaScript/CoffeeScript hooks to override and extend element updates/appends/removes for partials
• Support for Faye and Pusher

• Ruby >= 1.9.2
• Rails >= 3.1
• jQuery

gem 'faye'
gem 'thin'
gem 'sync'

gem 'pusher'
gem 'sync'

$ bundle
$ rails g sync:install

//= require sync

<%= javascript_include_tag Sync.adapter_javascript_url %>

Set your configuration in the generated config/sync.yml file, using the Faye adapter. Then run Faye alongside your app.

rackup sync.ru -E production

Set your configuration in the generated config/sync.yml file, using the Pusher adapter. No extra process/setup.

By Default, Sync runs in async mode, meaning all http post requests to the pubsub server will run in an eventmachine-http request, bypassing the need for a background job/worker and allowing the controller request-response times to remain unaffected by sync publishes. Running in async mode requires either an evented webserver like thin or manually running an eventmachine process in a seperate thread. For example, async mode works perfectly with unicorn using a configuration such as:

# config/unicorn.rb
worker_processes 3
preload_app true
timeout 30

before_fork do |server, worker|
  ActiveRecord::Base.connection.disconnect! if defined?(ActiveRecord::Base)
  EM.stop if defined?(EM) && EM.reactor_running?
end

after_fork do |server, worker|
  ActiveRecord::Base.establish_connection if defined?(ActiveRecord::Base)
  Thread.new { EM.run }
end

The current implementation uses a DOM range query (jQuery's nextUntil) to match your partial's "element" in the DOM. The way this selector works requires your sync'd partial to be wrapped in a root level html tag for that partial file. For example, this parent view/sync partial approach would not work:

Given the sync partial _todo_row.html.erb:

Title:
<%= link_to todo.title, todo %>

And the parent view:

<table>
  <tr>
    <%= sync partial: 'todo_row', resource: @todo %>
  </tr>
</table>

sync partial _todo_row.html.erb:

<tr> <!-- root level container for the partial required here -->
  Title:
  <%= link_to todo.title, todo %>
</tr>

And the parent view changed to:

<table>
  <%= sync partial: 'todo_row', resource: @todo %>
</table>

I'm currently investigating true DOM ranges via the Range object.

View sync/users/_user_list_row.html.erb

<tr>
  <td><%= link_to user.name, user %></td>
  <td><%= link_to 'Edit', edit_user_path(user) %></td>
  <td><%= link_to 'Destroy', user, method: :delete, remote: true, data: { confirm: 'Are you sure?' } %></td>
</tr>

View users/index.html.erb

<h1>Some Users</h1>
<table>
  <tbody>
    <%= sync partial: 'user_list_row', collection: @users %>
  </tbody>
</table>

Controller

def UsersController < ApplicationController
  …
  def update
    @user = User.find(params[:id])
    if user.save
    …
    end

    # Sync updates to any partials listening for this user
    sync_update @user

    redirect_to users_path, notice: "Saved!"
  end

  def destroy
    @user = User.find(params[:id])
    @user.destroy

    # Sync destroy, telling client to remove all dom elements containing this user
    sync_destroy @user

    respond_to do |format|
      format.html { redirect_to users_url }
      format.json { head :no_content }
    end
  end
end