Eventless

Eventless aspires to be a concurrent networking library for Ruby that lets you write asynchronous, event driven code that looks like normal, blocking code. It uses Fibers, so it requires Ruby 1.9. It also uses Marc Lehmann's libev via Tony Arcieri's cool.io. Eventless is inspired heavily by gevent.

Right now it's more of an experiment than an actual library, but I'm working hard on that.

##How it works

Eventless monkey patches Socket to make its API asynchronous. All of your code runs in a Fiber. You can make new fibers using Eventless.spawn. Fiber.new will not work. Your code should look exactly the same, but when you call something that normally blocks, your fiber gets put to sleep on the event loop and gets woken up when there is data to be read or written.

##How to use it

Because Eventless monkey patches the core library (eww, gross, I know), any networking library that is written in pure Ruby should just work (tm). Currently Eventless has enough code in it to support open-uri, so you can do things like this:

require 'eventless'
require 'open-uri'

# no async dns support yet, so we'll request IP addresses
# all of these are google.com
fibers = %w(74.125.226.240 74.125.226.241 74.125.226.242 74.125.226.243 74.125.226.244).map do |url|
  Eventless.spawn do
    open("http://#{url}/") { |f| puts f.read }
  end
end

fibers.each { |f| f.join }

You can also do this, which is admittedly, pretty silly:

require 'eventless'

fibers = []
5.times do
  fibers << Eventless.spawn { sleep 2 }
end

fibers.each { |f| f.join }

Even though you've spawned five fibers that sleep for two seconds a piece, this code should only take two seconds to run.

###Threads

Eventless has very experimental support for monkeypatching Thread.new to spawn a Fiber instead effectively turing multithreaded programs into single threaded, evented programs. This doesn't work well yet and it is currently an explicit opt-in by putting require 'eventless/thread' in your code.

##Install

It will probably crash or not work, but:

$ git clone git://github.com/davidbalbert/eventless.git
$ cd eventless/examples # run some of these

##Test

This doesn't really work yet, but here's the start. Eventless is going to test against rubyspec. Here's how you do it:

$ rake spec:deps # clones rubyspec and mspec
$ rake spec # right now this just runs the socket specs without eventless

By default mspec will test against the ruby binary. You can specify the binary name or path by setting TARGET:

$ TARGET=ruby19 rake spec
$ TARGET=/usr/local/bin/ruby rake spec

Remember, right now Eventless only works on Ruby 1.9.

##Status

###What works

The event loop
Exception handling in Fiber
Kernel#sleep
IO.select
Socket#recv, Socket#connect, Socket#write, and TCPSocket.new
IO#read* and IO#sysread (for sockets only)
IO#get* (but I haven't really tested them)
IO#write*
timeout.rb
open-uri

###What doesn't work

All the other Socket code.
DNS resolution
Everything else

##Contributing

The current goal is to replace all blocking methods in Socket with API compatible versions that transfer control to the event loop rather than block. When in doubt, read the code for gevent, but write your code like a Rubyist would.

##License

Eventless is licensed under the MIT License. See LICENSE for more information.

DanielleSucher/eventless

Eventless