PubSubHubbub_Publisher 1.0

PubSubHubbub_Publisher 1.0 is yet another excellent utility for everyone. It is actually a simple, open, server-to-server web-hook-based pubsub (publish/subscribe) protocol as a simple extension to Atom.

Parties (servers) speaking the PubSubHubbub protocol can get near-instant notifications (via webhook callbacks) when a topic (Atom URL) they're interested in is updated.

This tool works as follow:

1. An Atom URL (a "topic") declares its Hub server(s) in its Atom XML file, via . The hub(s) can be run by the publisher of the Atom, or can be a community hub that anybody can use.
2. A subscriber (a server that's interested in a topic), initially fetches the Atom URL as normal. If the Atom file declares its hubs, the subscriber can then avoid lame, repeated polling of the URL and can instead register with the feeds hub(s) and subscribe to updates.
3. The subscriber subscribes to the Topic URL from the Topic URLs declared Hub(s).
4. When the Publisher next updates the Topic URL, the publisher software pings the Hub(s) saying that there's an update.
5. The hub efficiently fetches the published feed and multicasts the new/changed content out to all registered subscribers.
6. The protocol is decentralized and free. No company is at the center of this controlling it. Anybody can run a hub, or anybody can ping (publish) or subscribe using open hubs.
7. To bootstrap this, the publisher has provided an open source reference implementation of the hub (the hard part of the protocol) that runs on Google App Engine, and is open for anybody to use.