> I figured that it might be useful to collect answers to all these
> questions, that periodically are asked in this mailing list in a blog post.
> Here it is:http://lbolla.info/blog/2012/10/03/asynchronous-programming-with-torn...
> If you have comments or you want me to add/correct something, just let me
> know.
> L.
> On Wed, Oct 3, 2012 at 7:04 AM, Ben Darnell <b...@bendarnell.com> wrote:
> > Your async_callback version doesn't actually work - it never calls
> > callback_sleep. async_callback is meant to be used as a wrapper to
> > deal with exception handling - it was necessary in early versions of
> > Tornado, but not any more. You probably meant io_loop.add_callback
> > instead of async_callback, but if you make that change you'll see that
> > time.sleep blocks in that version as well.
> > @asynchronous is a declaration, not a directive: it describes the
> > fact that get() is asynchronous (i.e. there is more work to be done
> > after it returns), it doesn't make it so. Tornado's core is still a
> > single-threaded event loop, so to achieve concurrency within a single
> > process you need to use or make non-blocking versions of any
> > time-consuming functions you use (e.g. IOLoop.add_timeout instead of
> > time.sleep, or AsyncHTTPClient instead of HTTPClient or urllib), or
> > hand that work off to another thread or process.
> > -Ben
> > On Tue, Oct 2, 2012 at 8:57 PM, Jimmy <li.jiam...@gmail.com> wrote:
> > > I don't mean to make it sleep. You can assume the sleep to some heavy
> > load
> > > work, like loop i from 0 to 10000000000. When multiple requests come in
> > > concurrently, I saw the request is executed in sequence, not in parallel
> > > (using yield gen.Task). But the old way of async_callback works.
> > > How to use gen.Task to create async behavior?
> > > On Wednesday, October 3, 2012 5:51:54 AM UTC+8, aliane abdelouahab wrote:
> > >> look here, maybe it will help:
> >http://groups.google.com/group/python-tornado/browse_thread/thread/ae...
> > >> On 2 oct, 11:08, Li jiaming <li.jiam...@gmail.com> wrote:
> > >> > I created a simple app with gen.task. But seems doesn't work
> > >> > asynchronously. I try to call /sleep for multiple times, but it
> > handles
> > >> > request in sequence.
> > >> > import tornado.ioloop
> > >> > import tornado.web
> > >> > from tornado.web import asynchronous
> > >> > from tornado import gen
> > >> > import time
> > >> > import tornado.httpserver
> > >> > class MainHandler(tornado.web.RequestHandler):
> > >> > def get(self):
> > >> > print 'receive root request'
> > >> > self.write("Hello, world")
> > >> > class SleepHandler(tornado.web.RequestHandler):
> > >> > @asynchronous
> > >> > @gen.engine
> > >> > def get(self):
> > >> > print 'receive sleep request'
> > >> > yield [ gen.Task(self.sleep, 10),
> > >> > gen.Task(self.sleep, 9)]
> > >> > self.write("Wake up")
> > >> > self.finish()
> > >> > def sleep(self, sec, callback):
> > >> > print 'sleep for %d seconds' % sec
> > >> > time.sleep(sec)
> > >> > print 'finish sleep %d' % sec
> > >> > return callback()
> > >> > application = tornado.web.Application([
> > >> > (r"/", MainHandler),
> > >> > (r"/sleep", SleepHandler),
> > >> > ])
> > >> > if __name__ == "__main__":
> > >> > server = tornado.httpserver.HTTPServer(application)
> > >> > server.listen(8888)
> > >> > tornado.ioloop.IOLoop.instance().start()
> > >> > *Anything wrong in my code?*
> > >> > I also tried async_callback (which is claimed to be obsoleted way of
> > >> > doing
> > >> > async). But it works. It can handle multiple requests in parallel when
> > >> > calling /sleep.
> > >> > class SleepHandler(tornado.web.RequestHandler):
> > >> > @asynchronous
> > >> > def get(self):
> > >> > print 'receive sleep request'
> > >> > self.async_callback(self.callback_sleep, 10)
> > >> > def callback_sleep(self, sec):
> > >> > print 'callback sleep for %d seconds' % sec
> > >> > time.sleep(sec)
> > >> > print 'finish callback sleep for %d seconds' % sec
> > >> > self.write('wake up')
> > >> > self.finish()
