Green

Cooperative multitasking for Ruby. Proof of concept.

Based on Ruby 1.9 Fibers, but unlike EM::Synchrony it uses symmetric coroutines (only #current and #transfer used) and HUB-orientend architecture. So coroutines transfer control to HUB and HUB transfer control to coroutines. Coroutines never tranfer control to each other.

In comparison with EM-Synchrony it allows:

• develop real complex cooperative multitasking apps;
• timeouts. Yes, in common case you cannot add timeout with EM-Synchrony;
• kill greens. And it safe unlike kill Threads;
• works with REPL and debugger. EM-Synchrony uses Fiber.yield, so you cannot run nothing in REPL;
• works with every environment. You can run nonblock web-applications with Unicorn;
• compatible with Ruby's Enumerator and with any other uses of Fibers themself (see https://github.com/igrigorik/em-synchrony/issues/114)

require 'green'
require 'green/group'
require 'green-em/em-http'

g = Green::Pool.new(size: 2)

urls = ['http://google.com', 'http://yandex.ru']

results = g.enumerator(urls) do |url|
  EventMachine::HttpRequest.new(url).get
end.map { |i| i.response }

p results

You can run it from Irb! ;)

You can add timeout:

require 'green'
require 'green/group'
require 'green-em/em-http'

g = Green::Pool.new(size: 2)

urls = ['http://google.com', 'http://yandex.ru']

begin
  Green.timeout(1) do
    results = g.enumerator(urls) do |url|
      EventMachine::HttpRequest.new(url).get
    end.map { |i| i.response }
    p results
  end
rescue Timeout::Error
  p "Timeout!"
end

You can use net/http (and any gem over it):

require 'green'
require 'green/group'
require 'green/monkey'
require 'net/http'

g = Green::Pool.new(size: 2)

hosts = ['google.com', 'yandex.ru']

results = g.enumerator(hosts) do |host|
  Net::HTTP.get host, '/'
end.map { |i| i }

p results

You can run nonblock Web application with any webserver:

require 'green'
require 'green/group'

app = proc do |env|
  start = Time.now
  g = Green::Group.new
  results = []
  g.spawn do
    Green.sleep 1
    results << :fiz
  end
  g.spawn do
    Green.sleep 1
    results << :buz
  end
  g.join
  [200, {"Content-Type" => 'plain/text'}, ["Execution time: #{Time.now - start}; Results: #{results.inspect}"]]
end
run app 

Run it with unicorn app.ru