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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}".format(t)
sleep(2)
t += 1
callback()
def on_finish(self):
print ("inside finish")
self.write("Long running job complete")
self.finish()
def main():
tornado.options.parse_command_line()
settings = {
"static_path": os.path.join(os.path.dirname(__file__), "static"),
}
application = tornado.web.Application([
(r"/", MainHandler),
(r"/longPolling", LongHandler)
], **settings
)
http_server = tornado.httpserver.HTTPServer(application)
http_server.listen(options.port)
tornado.ioloop.IOLoop.instance().start()
if __name__ == "__main__":
main()
This is server part. It has main view (shows little greeting, current server time and url for ajax query, that executes long running job. If you press a button, a long running job executes. And server hangs :( I can't view no pages, while this job is running. Here is template page:
<html>
<head>
<title>{{ title }}</title>
<script type="text/javascript" language="JavaScript" src="{{ static_url("js/prototype.js")}}"></script>
<script type='text/javascript' language='JavaScript'>
offset=0
last_read=0
function test(){
new Ajax.Request("http://172.22.22.22:8888/longPolling",
{
method:"get",
asynchronous:true,
onSuccess: function (transport){
alert(transport.responseText);
}
})
}
</script>
</head>
<body>
Current time is {{c_time}}
<br>
<input type="button" value="Test" onclick="test();"/>
</body>
</html>
what am I doing wrong? How can implement long pooling, using Tornado and Prototype (or jQuery)
PS: I have looked at Chat example, but it too complicated. Can't understand how it works :(
PSS Download full example
981
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.
170
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