How do you spawn an EventMachine "inside" a Rails app?

Question

I've got a Rails application, and am looking to add some sort of WebSocket support to it. From various googling, it appears that the best Ruby based WebSocket solution is em-websocket running on EventMachine.

I was wondering if there was a way to "integrate" an EventMachine reactor into Rails? Where do I put the initialization code? Is this the proper way to accomplish this?

I've seen this example that falls back on Sinatra to do an EventMachine GET request, but that isn't quite what I'm looking for.

Any help is appreciated.

Answer 1

You cannot run the Eventmachine engine inside of Rails itself as it is a persistent run loop that would block one of your Rails processes permanently. What is usually done is there's a side-process that uses Eventmachine and Rails communicates with it through sockets to send notifications.

Juggernaut serves as an example of this kind of thing where it implements a Websocket client and a Rails hook to send notifications to it. The project has since deprecated the Ruby version in favor of a JavaScript Node.js version but this still serves as a very thorough example of how Eventmachine can be used.