Google Fashioning PubSubHubbub as RSS on Steroids
by Clint Boulton
PubSubHubbub
The PubSubHubbub protocol has its own colorful logo. Check out the ensuing flow chart for how it works.
A Subscriber
A subscriber polls a publisher’s feed. The feed contains a forward link to the Hub.
The Subscriber
The subscriber posts a subscription request to the Hub. The request contains the URL where the Hub should post new updates.
The Hub
The Hub posts to the endpoint URL to verify the request was authentic. The subscriber then responds with confirmation to the Hub.
The Publisher
The publisher notifies the Hub about updates by posting feed URLs to the Hub. The Hub pulls the feed again to find new entries.
When the Publisher Does not Tell the Hub About Updates
If the publisher does not inform the Hub, the Hub will periodically poll the Publisher’s feed for new updates.
Receiving Feed Updates
When the Hub receives a new update to a feed, it posts the update to the Subscriber’s endpoint URL.
What if There Are Multiple Subscribers?
If feed X has multiple subscribers, the Hub sends updates to all of them.
The Distribution
The future is distributed: There will be big hubs, many small hubs and tons of publishers and subscribers. Publishers, subscribers and hubs may play multiple roles.
PubSubHubbub Requirements
This is what publishers, subscribers and hubs need for the protocol to work.