An adapter for Rack that makes it look like node

app.ru

##
# Make Rack look like node.
#
#  http://youtu.be/Zp91yUH-zAw
#
# Run like this:
#
#   $ unicorn -I. app.ru

require 'node_adapter'

use Rack::Chunked

run createServer { |req, res|
  res.writeHead(200, {'Content-Type' => 'text/plain'})
  10.times do
    res.chunk "hi mom!\n"
    sleep 0.5
  end
  res.end "Hello World\n"
}

node_adapter.rb

require 'thread'

class Adapter
  class Latch # :nodoc:
    def initialize
      @mutex = Mutex.new
      @cond  = ConditionVariable.new
      @released = false
    end

    def release
      @mutex.synchronize {
        @released = true
        @cond.broadcast
      }
    end

    def await
      @mutex.synchronize {
        @cond.wait @mutex unless @released
      }
    end
  end

  class Buffer < Struct.new(:q)
    def each
      while part = q.pop
        yield part
      end
    end
  end

  class << self; attr_accessor :block; end

  def self.call env
    new(block).call env
  end

  def initialize block
    @block        = block
    @code         = 200
    @header       = {}
    @body_written = Latch.new
    @q            = ::Queue.new
  end

  def call env
    Thread.new { @block.call(env, self) }

    # Wait for the child thread to write to the body,
    # effectively "closing" the response.
    @body_written.await
    [@code, @header, Buffer.new(@q)]
  end

  def writeHead code, header
    @code   = code
    @header = header
  end

  def chunk string
    @body_written.release
    @q.push string
  end

  def end string
    @body_written.release
    @q.push string
    @q.push nil
  end
end

def createServer &block
  Adapter.block = block
  Adapter
end