Python 队列链接对象运行 asyncio 协程与主线程输入

Question

我有一个脚本运行ning，其中主线程从标准输入获取输入，然后使用队列将其传递给子线程。在子线程中，我使用 asyncio 协同程序在套接字上启动侦听器并等待连接。建立连接后，我现在可以从主线程通过侦听器发送数据。

一切似乎都运行良好，但由于 asyncio.BaseEventLoop 不是线程安全的，我是否会运行遇到问题？

这是我尝试解决使用像 python 的带有 asyncio 的 cmd 模块的阻塞库的问题。

我的代码如下。

import sys
import asyncio
from time import sleep
from threading import Thread
from queue import Queue

stdin_q = Queue()

clients = {} # task -> (reader, writer)

def client_connected_handler(client_reader, client_writer):
    # Start a new asyncio.Task to handle this specific client connection
    task = asyncio.Task(handle_client(client_reader, client_writer))
    clients[task] = (client_reader, client_writer)

    def client_done(task):
        # When the tasks that handles the specific client connection is done
        del clients[task]

    # Add the client_done callback to be run when the future becomes done
    task.add_done_callback(client_done)

@asyncio.coroutine
def handle_client(client_reader, client_writer):
    # Handle the requests for a specific client with a line oriented protocol
    while True:

        cmd = yield from get_input()
        client_writer.write(cmd.encode())

        data = yield from client_reader.read(1024)

        print(data.decode(),end="",flush=True)

@asyncio.coroutine
def get_input():
  while True:
    try:
      return stdin_q.get()
    except:
      pass



class Control:

    def start(self):
        loop = asyncio.new_event_loop()
        asyncio.set_event_loop(loop)
        self.loop = asyncio.get_event_loop()

        server = self.loop.run_until_complete(asyncio.start_server(client_connected_handler, '0.0.0.0', 2222))
        self.loop.run_forever()
        self.stop()

    def stop(self):    
        self.loop.stop()
        self.loop.close()

def fire_control():
    con = Control()
    con.start()

if __name__ == "__main__":

    stdin_q.put("\n")
    t = Thread(target=fire_control)
    t.start()
    sleep(2)
    _cmd = ""
    while _cmd.lower() != "exit":
        _cmd = input("")
        if _cmd == "":
          _cmd = "\r\n"

        stdin_q.put(_cmd)

Answer 1

这不会很好地工作，因为对 stdin_q.get() 的调用将阻止您的事件循环。这意味着如果您的服务器有多个客户端，那么所有客户端都将被第一个到达 stdin_q.get() 的客户端完全阻塞，直到您将数据发送到队列中。解决这个问题的最简单方法是在后台 ThreadPoolExecutor 中使用 BaseEvent.loop.run_in_executor 到运行 stdin_q.get，这允许您等待它而不会阻塞事件循环：

@asyncio.coroutine
def get_input():
    loop = asyncio.get_event_loop()
    return (yield from loop.run_in_executor(None, stdin_q.get))  # None == use default executor.

编辑 (1/27/16)：

有一个名为 janus 的库，它提供了一个异步友好、线程安全的队列实现。

使用该库，您的代码将如下所示（我省略了未更改的部分）：

...
import janus

loop = asyncio.new_event_loop()
stdin_q = janus.Queue(loop=loop)
...

@asyncio.coroutine
def get_input():
  loop = asyncio.get_event_loop()
  return (yield from stdin_q.async_q.get())

class Control:

    def start(self):
        asyncio.set_event_loop(loop)
        self.loop = asyncio.get_event_loop()

        server = self.loop.run_until_complete(asyncio.start_server(client_connected_handler, '0.0.0.0', 2222))
        self.loop.run_forever()
        self.stop()

    def stop(self):    
        self.loop.stop()
        self.loop.close()

...

if __name__ == "__main__":

    stdin_q.sync_q.put("\n")
    t = Thread(target=runner)
    t.start()
    sleep(2)
    _cmd = ""
    while _cmd.lower() != "exit":
        _cmd = input("")
        if _cmd == "":
          _cmd = "\r\n"

        stdin_q.sync_q.put(_cmd)

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