Facebook® Application Development For Dummies®

Finding the Hubbub about PubsubHubbub

At the time of this writing, one of the more popular real-time updating services is a protocol called PubsubHubbub. As funny as the name sounds, It's actually quite an efficient way of subscribing to real-time updates, with the capability to insert a “hub” in the middle so that the content provider doesn't have to do all the heavy work if it doesn't want to.

A typical PubsubHubbub workflow involves a subscriber, a hub, and a publisher. It works like this (see Figure 11-1):

1. The subscriber does a typical RSS or Atom request to the publisher's feed.

   The publisher's feed includes an item in the feed, directing the subscriber to a hub for that feed where it can subscribe to get future updates.

2. The subscriber notifies the hub, via the specified URL, that it wants to get updates from the publisher.

   The subscriber sends the hub a URL that the hub can notify the subscriber with when it has new updates.

3. When the publisher has new updates, it notifies the hub that it has new updates. The hub then requests those updates, and the publisher sends those updates to the hub.
4. The hub then posts the new update to the subscriber via the URL that the subscriber sent to the hub in Step 2.

   If multiple subscribers exist, the hub posts to all the subscribers.

The goal of PubsubHubbub is to provide a means for publishers to reduce the load on their servers through one or multiple hubs through which subscribers can subscribe.

Figure 11-1: The general workflow of a ...