It persists messages in one direction. Imagine you have a publish subscribe situation where you have a few apps subscribed to a publisher. If one of those apps goes down, the publisher will make a note and store the messages until it comes back. When the app comes back, it will get all the messages it missed. It's really a wonderful thing if you were going to implement peer-to-peer pub/sub yourself.
It's also nice in applications like Mongrel2. Make an http request, in your browser, start up your web server, and the request completes! Great for development, where sometimes you switch to the browser faster than your app can restart after a change. With Mongrel2 (and thanks to 0MQ), you don't even notice the race condition.
It's also nice in applications like Mongrel2. Make an http request, in your browser, start up your web server, and the request completes! Great for development, where sometimes you switch to the browser faster than your app can restart after a change. With Mongrel2 (and thanks to 0MQ), you don't even notice the race condition.