Dishes is a Rack-based Ruby framework that makes it easy to write real-time web applications.
Classically, the HTTP protocol is strictly request/response based. The client always sends a request first; the server can't send data to a client arbitrarily. Workarounds using Ajax exist (such as long polling), but they almost always tie up a whole connection until the server has something to say. Some browsers allow only a small number of active connections, placing a heavy upper-limit on what can be done simultaneously.
Dishes takes a different approach to this problem, requiring only two connections. One connection is used to send a request to the server, which is immediately closed so it can be reused. A second connection uses long-polling to stay open, which the server uses to send results back to the client. Whenever the long-polling connection is closed, it is re-opened to wait for updates. (This is the same model that the BOSH protocol uses.) This makes Dishes a perfect fit for rich applications like real-time chat and other applications with a lot of client/server communication.
Dishes is written specifically for my needs, so it may not fit yours exactly. There are other Comet-based alternatives, including (but not limited to):
- [node.js](http://nodejs.org/ Node.js) - An asynchronous server-side framework written in Javascript.
- [Meteor](http://meteorserver.org/ Meteor Server) - A Comet server written in Perl.
Dishes can be dropped right into a Rack server with minimal pain, coexisting with other applications (such as a Sinatra app) on the same port and domain. You only need to map one URL to a Dishes app, for example "/dishes".
Dishes is under heavy development at this time, so there is no official RubyGems package. Feel free to clone or fork it and play around though!
At this time, Thin is required to use Dishes. Hopefully other (evented) webservers will be supported in the future!
See basic.ru for the current target syntax/feature-set. It's practically guaranteed not to work at this time, but it paints a pretty picture.
The name "Dishes" is an extraordinarily lame pun. "Asynchronous" sounds like it has a "sink" in it, and sinks contain dishes. See, I told you it was lame.