async applications test those with `ab -n 10 -c 10` it should take around 1 sec (and not 10) : http://yoan.dosimple.ch/blog/2010/04/24/

eventlet_app.py

from eventlet import sleep, wsgi, listen

def application(environ, start_response):
    start_response("200 OK", [("Content-Type", "text/plain")])
    sleep(1)
    return ["Hello, world!"]

def main():
    wsgi.server(listen(('', 8000)), application)

if __name__ == "__main__":
    main()

gevent_app.py

from gevent import sleep, wsgi

def application(environ, start_response):
    start_response("200 OK", [("Content-Type", "text/plain")])
    sleep(1)
    return ["Hello, world!"]

def main():
    wsgi.WSGIServer(('', 8000), application).serve_forever()

if __name__ == "__main__":
    main()

node.js

var http = require("http");

http.createServer(function(req, res){
    res.writeHead(200, {"Content-Type": "text/html"});
    setTimeout(function(){
        res.end("Hello, world!")
    },1000)
}).listen(8000);

thin_em.ru

class DeferrableBody
  include EventMachine::Deferrable

  def call(body)
    body.each do |chunk|
      @body_callback.call(chunk)
    end
  end

  def each &block
    @body_callback = block
  end
end

app = proc do |env|
  body = DeferrableBody.new
  
  EventMachine::next_tick do
    env["async.callback"].call [200,
                                {"Content-Type" => "text/html"},
                                body]
  end
  
  EventMachine::add_timer(1) do
     body.call ["Hello, world!"]
     body.succeed
  end

  [-1, {}, []]
end

run app

tornado_app.py

import time

import tornado.httpserver
import tornado.ioloop
import tornado.options
import tornado.web

from tornado.options import define, options

define("port", default=8000, help="run on the given port", type=int)

class MainHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous 
    def get(self):
        tornado.ioloop.IOLoop.instance().add_timeout(
            time.time() + 1,
            self.async_callback(self.later))

    def later(self):
        self.write("Hello, world!")
        self.finish()

urls = (
    (r"/", MainHandler),
)

application = tornado.web.Application(urls)

def main():
    tornado.options.parse_command_line()
    http_server = tornado.httpserver.HTTPServer(application)
    http_server.listen(options.port)
    tornado.ioloop.IOLoop.instance().start()

if __name__ == "__main__":
    main()

twisted_app.py

from twisted.web import server, resource
from twisted.internet import reactor, task

class Root(resource.Resource):
    isLeaf = True
    def render_GET(self, request):
        d = task.deferLater(reactor, 1, lambda: request)
        d.addCallback(self.output)
        return server.NOT_DONE_YET
    
    def output(self, request):
        request.write("Hello, world!")
        request.finish()

site = server.Site(Root())
reactor.listenTCP(8000, site)
reactor.run()