在无协程函数中，如何从 Tornado TCP 的协程函数中获取返回值？

Question

我用 Tornado TCP 编写了 3 段代码。我遇到了一些困难。

我的代码如下：

client.py

'''tcp client'''


from socket import socket, AF_INET, SOCK_STREAM
s = socket(AF_INET, SOCK_STREAM)
s.connect(('localhost', 20000))
resp = s.recv(8192)
print('Response:', resp)
s.send(b'Hello\n')
s.close()

server.py

'''tcp server'''

#! /usr/bin/env python
#coding=utf-8

from tornado.tcpserver import TCPServer
from tornado.ioloop import IOLoop
from tornado.gen import *

clientDict=dict()        #save infomation of client

class TcpConnection(object):
    def __init__(self,stream,address):
        self._stream=stream
        self._address=address
        self._stream.set_close_callback(self.on_close)

    @coroutine
    def send_messages(self):
        yield self.send_message(b'world \n')
        response = yield self.read_message()

        return response


    def read_message(self):
        return self._stream.read_until(b'\n')

    def send_message(self,data):
        return self._stream.write(data)

    def on_close(self):
        global clientDict
        clientDict.pop(self._address)
        print("the monitored %d has left",self._address)

class MonitorServer(TCPServer):
    @coroutine
    def handle_stream(self,stream,address):
        global clientDict
        print("new connection",address,stream)
        clientDict.setdefault(address, TcpConnection(stream,address))



if __name__=='__main__':
    print('server start .....')
    server=MonitorServer()
    server.listen(20000)
    IOLoop.instance().start()

ma​​in.py

import time
from threading import Thread
import copy
from server import *

def watchClient():
    '''call the "send" function when a new client connect''

    global clientDict
    print('start watch')
    lastClientList=list()
    while True:
        currentClientList=copy.deepcopy([key for key in clientDict.keys()])
        difference=list(set(currentClientList).difference(set(lastClientList)))

        if len(difference)>0:
            send(difference)
            lastClientList=copy.deepcopy(currentClientList)
            time.sleep(5)
        else:
            time.sleep(5)
            continue

def send(addressList):
    '''send message to a new client and get response'''
    global clientDict
    for address in addressList:
        response=clientDict[address].send_messages()
        print(address," response :",response)

def listen():
    server=MonitorServer()
    server.listen(20000)
    IOLoop.instance().start()


if __name__=='__main__':
    listenThread=Thread(target=listen)
    watchThead=Thread(target=watchClient)
    watchThead.start()
    listenThread.start()

我想获取main.py运行时的“打印信息”---address,response:b'hello\n'

但实际上我得到的“打印信息”为----

('127.0.0.1', 41233)  response :<tornado.concurrent.Future object at 0x7f2894d30518>

它不能返回 b'hello\n'。

那我猜它无法从协程函数（@coroutine def send_messages(self))。

如何解决？

顺便说一句，我想知道如何使 clientDict 成为 class MonitorServer 的属性，而不是全局属性。 请帮我！谢谢。

Answer 1

一般来说，任何调用协程的东西都应该是协程本身。混合线程和协程可能非常棘手；大多数基于协程的代码故意不是线程安全的。

从非协程函数在不同的线程调用协程的正确方法是这样的：

def call_coro_from_thread(f, *args, **kwargs):
    q = queue.Queue()
    def wrapper():
        fut = f(*args, **kwargs)
        fut.add_done_callback(q.put)
    IOLoop.instance().add_callback(wrapper)
    fut = q.get()
    return fut.result()

IOLoop.add_callback是安全的将控制权转移到IOLoop线程所必需的，然后使用Queue将结果传回。