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[英]How does asyncio main thread manage running either the event loop and coroutines at the same time?
[英]Python queue linking object running asyncio coroutines with main thread input
我有一个脚本运行,其中主线程从stdin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协同程序来启动套接字上的侦听器并等待连接。 一旦建立连接,我现在可以通过主线程中的侦听器发送数据。
这一切似乎都运行得很好,但由于asyncio.BaseEventLoop不是线程安全的,我会遇到问题吗?
这是我尝试解决使用像python的cmd模块和asyncio这样的阻塞库的问题。
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)
这不会stdin_q.get()
,因为对stdin_q.get()
的调用会阻止你的事件循环。 这意味着如果您的服务器有多个客户端,那么所有这些客户端都会被首先到达stdin_q.get()
所有客户端完全阻止,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使用BaseEvent.loop.run_in_executor
在后台ThreadPoolExecutor
运行stdin_q.get
,它允许您在不阻塞事件循环的情况下等待它:
@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asyncio友好的,线程安全的队列实现。
使用该库,您的代码将如下所示(我遗漏了未更改的部分):
...
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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