I came across a publisher\subscriber protocol called PubSubHubBub. It is a server-to-server web-hook-based pubsub (publish/subscribe) protocol - an extension to Atom and RSS. Here the parties (servers) get an instant notification when a feed URL, that they are interested in is updated. Traditionally a subscriber would subscribe to a feed and poll for it at regular intervals, to see if there is an updated feed available. In this protocol rather than polling for a feed, the content is pushed out from the publisher. The theory here is that the subscriber can subscribe to a feed via a 'Hub', which then would inform the subscribers when the feed is updated. How PubSubHubBub works? A Publisher instead of sending an update to every subscriber, it includes a in its feed URL and sends an update to the Hub . A Subscriber sends a subscription request to the Hub with the feed URL that it is interested in. The request also contains a callback URL to which the Hub should send an up...
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