“With all the recent buzz about real-time web, surely this is the year XMPP/AMQP Publish-Subscribe (PubSub) makes it to the big leagues! Or maybe not. Ejabberd (XMPP), RabbitMQ (AMQP) and other pubsub server implementations have come a long way but they remain cumbersome to setup and maintain, and perhaps more importantly, the clients require special libraries and a steep learning curve. That is not to say that either XMPP or AMQP are doomed for failure, in fact, they will continue to thrive, but there is a great case for a simplified PubSub implementation to cover the ad-hoc cases where a dedicated TCP channel might be an overkill: enter Webhooks.
The best part about Webhooks is that most of us are already familiar with them: callbacks over HTTP. Pioneered by PayPal and Subversion as a way to send real-time notifications to the client, they have found their way into many dozens of products we all use every day. Need pre or post commit hooks for your SVN or Git repository? Both GitHub and SVN support HTTP callbacks. Need a payment alert from PayPal, or an alert when a wiki page is modified? There are webhooks for that too. This simple mechanism allows us to build web services that work together via a simple and ubiquitous protocol we can all understand: HTTP!”