如何在Python3中与asyncio共享套接字？

Question

I need to use asyncio with os.fork() method for sharing socket between subprocess.

There is a heavy_jobs() function in data_received() callback, which will occupy a lot of CPU time.

import asyncio

class EchoClientProtocol(asyncio.Protocol):
    def __init__(self, message, loop):
        self.message = message
        self.loop = loop

    def data_received(self, data):
        heavy_jobs()

loop = asyncio.get_event_loop()
message = 'Hello World!'
coro = loop.create_connection(lambda: EchoClientProtocol(message, loop),
                              '127.0.0.1', 8000)
loop.run_until_complete(coro)
loop.run_forever()
loop.close()

In traditional method, we could use fork() to share socket between subprocess and parent:

bind(...);
listen(...);
pid = fork();

So, how could I do the same thing in asyncio ?

Answer 1

Currently asyncio does not support fork while the event loop is running ( https://bugs.python.org/issue21998 ). You must fork and then create the loop. A simple EchoClient with two processes:

import asyncio
import os
import socket

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(('127.0.0.1', 7777))
pid = os.fork()

class EchoClientProtocol(asyncio.Protocol):
    def __init__(self, message, loop):
        self.message = message
        self.loop = loop

    def data_received(self, data):
        print('Received in %s' % pid)

loop = asyncio.get_event_loop()
message = 'Hello World!'
coro = loop.create_connection(lambda: EchoClientProtocol(message, loop), sock=sock)
loop.run_until_complete(coro)
loop.run_forever()
loop.close()

And simple test - run nc -k -l 7777 , then start the client (code above).

If you also want to write a server, just change connect with socket.bind and socket.listen and of course asyncio.create_server