tornado.websocket和[Errno 24]太多打开的文件

Question

I have got and error ( [Errno 24] Too many open files ) while testing tornado.websocket on a local machine.

server.py

import tornado.ioloop
import tornado.web
import tornado.websocket
import tornado.options


class ChatSocketHandler(tornado.websocket.WebSocketHandler):
    waiters = set()

    def open(self):
        ChatSocketHandler.waiters.add(self)
        print "Clients: ", len(ChatSocketHandler.waiters)

    def on_close(self):
        ChatSocketHandler.waiters.remove(self)

    @classmethod
    def send_updates(cls, chat):
        for waiter in cls.waiters:
            try:
                waiter.write_message(chat)
            except:
                logging.error("Error sending message", exc_info=True)

    def on_message(self, message):
        ChatSocketHandler.send_updates(message)

app = tornado.web.Application([
    (r"/ws", ChatSocketHandler)
])

def main():
    tornado.options.parse_command_line()
    app.listen(8888)
    tornado.ioloop.IOLoop.instance().start()

if __name__ == "__main__":
    main()

clients.py (using websocket-client )

from multiprocessing import Pool, Process
from websocket import create_connection

def go():
    ws = create_connection("ws://127.0.0.1:8888/ws")

    while True:
        try:
            ws.send("Message ...")
            result =  ws.recv()
            print "Received '%s'" % result
        except KeyboardInterrupt:
            break
    ws.close()


for i in range(1000):
    Process(target=go).start()

The server dies after ~800 connections ;/

Additional question: is it ok to set up a Nginx proxy to a tornado server instance? Do I get some benefits?

Answer 1

Your process likely runs out of file descriptors. Here is a recipe for network tuning on Linux including how to increase max. FDs. (This is for Crossbar.io , but will work for Tornado also).

As to your question "does it make sense to put Nginx in front of Tornado": yes, definitely. Tornado's native TLS support is limited. Have a look at Hynek Schlawack: The Sorry State of SSL - PyCon 2014

Note: the latter does not apply to Twisted (or Crossbar.io, which is based on Twisted) - since Twisted uses pyOpenSSL and can be made to have high-quality TLS. So there is no need for Nginx with these (at least not for TLS reasons).