python龙卷风websocket错误：RuntimeError：线程'Thread-1'中没有当前事件循环

Question

i have the following code, it run well on Tornado <5 but it run into failure if i run it by Tornado>= 5,

import tornado.httpserver
import tornado.ioloop
import threading
import tornado.web,tornado.websocket

class thr(threading.Thread):
    def __init__(self,handler):
        self.handler=handler
        threading.Thread.__init__(self)
    def run(self):
        self.handler.write_message("test")
class ClientWebSocketConnectionHandler(tornado.websocket.WebSocketHandler):
    def open(self):
            print ("opened")
    def on_message(self, message):
            thr(self).start()    

class MainApplication(tornado.web.Application):
    def __init__(self):
        handlers = [(r'/User', ClientWebSocketConnectionHandler),]
        tornado.web.Application.__init__(self, handlers,)

TheShieldsWebSocket = MainApplication()
server = tornado.httpserver.HTTPServer(TheShieldsWebSocket)
server.listen(8085,'0.0.0.0')
tornado.ioloop.IOLoop.instance().start()

Error says: RuntimeError: There is no current event loop in thread 'Thread-1'

what the hell wrong with? it looks like it has something to do with the thread.

Answer 1

Assume you want write a api, this api may be need to wait something before render to the client side! here are serval way to achieve that! as you have use thread and this is good but no recommend. so we have invoke concurrent in tornado, you can see detail here .

And here you code can be modify as below:

import tornado.httpserver
import tornado.ioloop
import tornado.web,tornado.websocket


class ClientWebSocketConnectionHandler(tornado.websocket.WebSocketHandler):
    def open(self):
            print ("opened")
    def on_message(self, message):
            self.write_message('test')    

class MainApplication(tornado.web.Application):
    def __init__(self):
        handlers = [(r'/User', ClientWebSocketConnectionHandler),]
        tornado.web.Application.__init__(self, handlers,)

TheShieldsWebSocket = MainApplication()
server = tornado.httpserver.HTTPServer(TheShieldsWebSocket)
server.listen(8085,'0.0.0.0')
tornado.ioloop.IOLoop.instance().start()

Typical, you will got a 403 error, in that situation you can add a function name as check_origin .

    # rest of above code
    def check_origin(self, param):
            return True

    def open(self):
            print ("opened")
    def on_message(self, message):
            self.write_message('test') 

And then if you want you server can handler multi connection, you can use `concurrent way to do that like below :

    @gen.coroutine
    def on_message(self, message):
            http_client = AsyncHTTPClient()
            response = yield http_client.fetch("http://example.com")
            do_something_with_response(response)
            self.write_message('test')