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Google Fashioning PubSubHubbub as RSS on Steroids
by Clint Boulton
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PubSubHubbub
The PubSubHubbub protocol has its own colorful logo. Check out the ensuing flow chart for how it works.
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A Subscriber
A subscriber polls a publisher's feed. The feed contains a forward link to the Hub.
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The Subscriber
The subscriber posts a subscription request to the Hub. The request contains the URL where the Hub should post new updates.
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The Hub
The Hub posts to the endpoint URL to verify the request was authentic. The subscriber then responds with confirmation to the Hub.
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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.
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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.
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Receiving Feed Updates
When the Hub receives a new update to a feed, it posts the update to the Subscriber's endpoint URL.
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What if There Are Multiple Subscribers?
If feed X has multiple subscribers, the Hub sends updates to all of them.
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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.
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PubSubHubbub Requirements
This is what publishers, subscribers and hubs need for the protocol to work.
