Fullly stopping a threaded tornado WebSocket server

Question

For testing a WebSocket client, I am writing a small tornado WebSocket server, which resides in a designated thread and can be started and stopped during test runtime. Here is what I have come up with so far:

class SocketHandler(tornado.websocket.WebSocketHandler):
    def __init__(self, application, request, **kwargs):
        super().__init__(application, request, **kwargs)
        self.authenticated = False

    def check_origin(self, origin):
        return True

    def open(self):
        pass

    def on_message(self, message):
        pass

    def on_close(self):
        pass


application = tornado.web.Application([
    (r"/ws", SocketHandler),
])

class WebSocketServer(threading.Thread):
    def __init__(self, port):
        threading.Thread.__init__(self, name='WebServer')
        self.port = port
        self.ioloop = None

    def run(self):
        self.ioloop = tornado.ioloop.IOLoop()

        http_server_api = tornado.httpserver.HTTPServer(application)
        http_server_api.listen(self.port)

        self.ioloop.start()

        http_server_api.stop()
        self.ioloop.clear_instance()

    def stop(self):
        self.ioloop.add_callback(self.ioloop.stop)

Starting the server works well:

server = WebSocketServer(8888)
server.start()  

I can conncet to the server using any WebSocket client. Unfortunately, when I stop the server:

server.stop()

the thread closes, the listen port of the server is being removed, but all established WebSocket connections remain intact. How can I close all established connections as well? Thanks for the help!

Answer 1

In Tornado 5.1 there's no easy way to do this for websocket connections (for regular HTTP there's HTTPServer.close_all_connections). You'll just have to keep track of all your connections and explicitly close them. Tornado's own test suite jumps through a lot of ugly hoops to make this work without spamming the logs with warnings about unclean shutdown.

In Tornado 6.0 I want to fix this so that HTTPServer.close_all_connections is aware of websocket connections and closes them too.