Programming Social Applications

The Benefits: From Publishers to Subscribers

The PubSubHubbub specification offers a number of benefits to both publishers and subscribers for using a distributed hub-based system. Let’s take a look at a few.

Publisher: No repeated polling from multiple sources

The major benefit that publishers gain from this type of system is the fact that subscribers no longer need to periodically poll the publisher to check for updates to content they are interested in. A single subscriber making requests at regular intervals does not incur a lot of load, but if there are thousands of subscribers all continually requesting updated content from the publisher at regular intervals, it’s easy to imagine how heavy the load can get on the publisher’s side.

This burden on the publisher wouldn’t be so bad if subscribers only made single requests once the content has changed, but the only way for subscribers to know that is to make a request to the provider, creating a Catch-22 situation. This is the point, and role, of the hub in this specification. Subscribers subscribe to the hub only once for a given feed, and when the publisher pushes updates to the hub, it will in turn notify the subscribers of the update. Although the hub may periodically poll the publisher’s feeds if the publisher does not notify the hub of updates, this is only a single request source for a potentially large number of subscribers.

Subscriber: No need for repeated polling

On the other side of the fence, the largest benefit from the ...