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Handle pub/sub messaging through private channels in Rails.
Ruby JavaScript
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README.rdoc

Private Pub

Private Pub is a Ruby gem for use with Rails to publish and subscribe to messages through Faye. It allows you to easily provide real-time updates through an open socket without tying up a Rails process. All channels are private so users can only listen to events you subscribe them to.

This project was motivated by RailsCasts episode #260.

Setup

Add the gem to your Gemfile and run the bundle command to install it.

gem "private_pub"

Run the generator to create the initial files.

rails g private_pub:install

Add the generated JavaScript to your layout file. This can be used with any JavaScript framework.

<%= javascript_include_tag "private_pub" %>

Next, install and start up Faye using the rackup file that was generated.

gem install faye
rackup faye.ru -s thin -E production

It's not necessary to include faye.js since that will be handled automatically for you.

Usage

Use the subscribe_to helper method on any page to subscribe to a channel.

<%= subscribe_to "/messages/new" %>

Use the publish_to helper method to send JavaScript to that channel. This is usually done in a JavaScript AJAX template (such as a create.js.erb file).

<% publish_to "/messages/new" do %>
  $("#chat").append("<%= escape_javascript render(@messages) %>");
<% end %>

This JavaScript will be immediately evaluated on all clients who have subscribed to that channel. In this example they will see the new chat message appear in real-time without reloading the browser.

Alternative Usage

If you prefer to work through JSON instead of JavaScript templates to handle AJAX responses, you can pass an argument to publish_to instead of a block and it will be converted to_json behind the scenes. This can be done through the controller.

publish_to "/messages/new", :chat_message => "Hello, world!"

And then handle this through JavaScript on the client side.

PrivatePub.subscribe("/messages/new", function(data, channel) {
  $("#chat").append(data.chat_message);
});

The Ruby subscribe_to call is still necessary with this approach to grant the user access to the channel. The JavaScript is just a callback for any custom behavior.

Security

Security is handled automatically for you. Only the Rails app is able to publish messages. Users are only able to receive messages on the channels you subscribe them to so every channel is private.

Here's how it works. The subscribe_to helper will output a script element containing data information about the channel.

<script type="text/javascript">
  PrivatePub.sign({
    channel: "/messages/new",
    timestamp: 1302306682972,
    signature: "dc1c71d3e959ebb6f49aa6af0c86304a0740088d",
    server: "http://localhost:9292/faye"
  });
</script>

The signature is a combination of the channel, timestamp, and secret token set in the Rails app. This is checked by the Faye extension when subscribing to a channel to ensure the signature is correct. The signature is automatically expired after 1 hour but this can be configured in the generated YAML file.

signature_expiration: 600 # 10 minutes, expressed in seconds

Or use a blank value for no expiration.

signature_expiration:

Note: if Faye is on a separate server from the Rails app it's important that the system clocks be in sync so the expiration works properly.

Development & Feedback

Questions or comments? Please use the issue tracker. If you would like to contribue to this project, clone this repository and run bundle and rake to run the tests.

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