Faye Presence

Presence channels are an addition to Faye implemented via an extension and monitoring Faye events.

Getting Started

Install faye-presence:

$ npm install faye-presence --save

After creating your Faye server, install the faye-presence plugin:

var presence = require('faye-presence');

//...

var faye = new Faye.NodeAdapter(options);
presence.setup(faye, faye.getClient(), {
  servers: [ 'localhost:6379' ]
});

servers is an array of redis hostname/ports to use for storing presence data.

When a user subscribes to a channel starting with /presence/, they should also include in the message some presence information. (This is done using a Faye client plugin.) The outgoing subscription message should include an ext field that looks like this:

{
  ext: {
    presence: {
      id: 'username',
      data: {
        name: 'John Doe',
        avataur: 'http://example.com/avatar.png'
      }
    }
  }
}

The data field is optional and can be a javscript object with whatever information you want. It is persisted in Redis as long as that client is subscribed to that channel.

The subscription confirmation message from the server will then include a list of everyone current subscribed to that channel. Again, this needs to be intercepted using a client plugin:

{
  ext: {
    presence: {
      subscribe: {
        $id: $data,
        $id: $data,
        ...
      }
    }
  }
}

Whenever somebody new subscribes or unsubscribes from the channel, a message will be posted to the channel and delivered to all subscribers:

{
  subscribe: {
    $id: $data,
    ...
  },
  unsubscribe: {
    $id: null,
    ...
  }
}

The presence id is used instead of the internal Faye client id because it can more accurately identify an entity, where the Faye client id identifies a connection. A user can be subscribed concurrently on several browsers, and will not show as unsubscribed until all connections are closed.

Running tests:

Using docker-compose:

docker-compose run node npm test