Asynchronous COMET query with Tornado and Prototype

Question

I'm trying to write simple web application using Tornado and JS Prototype library. So, the client can execute long running job on server. I wish, that this job runs Asynchronously - so that others clients could view page and do some stuff there. Here's what I've got: ``` #!/usr/bin/env/ python import tornado.httpserver import tornado.ioloop import tornado.options import tornado.web from tornado.options import define, options import os import string from time import sleep from datetime import datetime define("port", default=8888, help="run on the given port", type=int) class MainHandler(tornado.web.RequestHandler): def get(self): self.render("templates/index.html", title="::Log watcher::", c_time=datetime.now()) class LongHandler(tornado.web.RequestHandler): @tornado.web.asynchronous def get(self): self.wait_for_smth(callback=self.async_callback(self.on_finish)) print("Exiting from async.") return def wait_for_smth(self, callback): t=0 while (t < 10): print "Sleeping 2 second, t={0}".f…

Accepted Answer

Tornado is single-threaded web server. Your while loop in `wait_for_smith` method is blocking Tornado.

You can rewrite that method like this:

```
def wait_for_smth(self, callback, t=10):
    if t:
        print "Sleeping 2 second, t=%s" % t
        tornado.ioloop.IOLoop.instance().add_timeout(time.time() + 2, lambda: self.wait_for_smth(callback, t-1))
    else:
        callback()
```

You need to add `import time` at the top to make this work.

Asynchronous COMET query with Tornado and Prototype

Solution

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