获取一个asyncio服务器来调用另一台服务器

Question

所以我修改了asyncio客户端和服务器（在这里找到：https://docs.python.org/3/library/asyncio-protocol.html#protocol-example-tcp-echo-server-and-client）的例子，我只想让client.py调用serverone.py，然后调用它来调用servertwo.py。

client.py

#!/usr/bin/env python3.4 
import asyncio 

class EchoClient(asyncio.Protocol): 
    message = 'This is the Client' 

    def connection_made(self, transport): 
     transport.write(self.message.encode()) 

    def data_received(self, data): 
     print('data received: {}'.format(data.decode())) 

    def connection_lost(self, exc): 
     asyncio.get_event_loop().stop() 

loop = asyncio.get_event_loop() 
coro = loop.create_connection(EchoClient, '127.0.0.1', 8888) 
loop.run_until_complete(coro) 
loop.run_forever() 
loop.close() 

serverone.py

#!/usr/bin/env python3.4 

import asyncio 

class EchoClient(asyncio.Protocol): 
    message = 'Server One sending message' 

    def connection_made(self, transport): 
     transport.write(self.message.encode()) 

    def data_received(self, data): 
     print('data received: {}'.format(data.decode())) 

    def connection_lost(self, exc): 
     asyncio.get_event_loop().stop() 

class EchoServer(asyncio.Protocol): 
    def connection_made(self, transport): 
     peername = transport.get_extra_info('peername') 
     self.transport = transport 

    def data_received(self, data): 
     loop = asyncio.get_event_loop() 
     coro = loop.create_connection(EchoClient, '127.0.0.1', 8889) 
     loop.run_until_complete(coro) 
     # close the socket 
     self.transport.close() 
     loop.close() 

loop = asyncio.get_event_loop() 
coro = loop.create_server(EchoServer, '127.0.0.1', 8888) 
server = loop.run_until_complete(coro) 
try: 
    loop.run_forever() 
except KeyboardInterrupt: 
    print("exit") 
finally: 
    server.close() 
    loop.close() 

servertwo.py

#!/usr/bin/env python3.4 

import asyncio 

class EchoServer(asyncio.Protocol): 
    def connection_made(self, transport): 
     peername = transport.get_extra_info('peername') 
     self.transport = transport 

    def data_received(self, data): 
     print('data received: {}'.format(data.decode())) 
     self.transport.write(data) 
     # close the socket 
     self.transport.close() 

loop = asyncio.get_event_loop() 
coro = loop.create_server(EchoServer, '127.0.0.1', 8889) 
server = loop.run_until_complete(coro) 
try: 
    loop.run_forever() 
except KeyboardInterrupt: 
    print("exit") 
finally: 
    server.close() 
    loop.close() 

我启动servertwo.py和serverone.py，然后拨打client.py。事情有部分工作;客户端不会调用serverone这确实通话servertwo，但随后serverone失败，此错误：

Exception in callback <bound method _SelectorSocketTransport._read_ready of <asyncio.selector_events._SelectorSocketTransport object at 0x7fbf4453b048>>() 
handle: Handle(<bound method _SelectorSocketTransport._read_ready of <asyncio.selector_events._SelectorSocketTransport object at 0x7fbf4453b048>>,()) 
Traceback (most recent call last): 
    File "/usr/lib64/python3.4/asyncio/events.py", line 39, in _run 
    self._callback(*self._args) 
    File "/usr/lib64/python3.4/asyncio/selector_events.py", line 458, in _read_ready 
    self._protocol.data_received(data) 
    File "./serverone.py", line 25, in data_received 
    loop.run_until_complete(coro) 
    File "/usr/lib64/python3.4/asyncio/base_events.py", line 203, in run_until_complete 
    self.run_forever() 
    File "/usr/lib64/python3.4/asyncio/base_events.py", line 179, in run_forever 
    raise RuntimeError('Event loop is running.') 
RuntimeError: Event loop is running. 

文档没有涵盖了很多的奇怪的使用情况，所以我有点卡住了。我应该使用asyncio.async拨打电话吗？我是否正确地处理了这个问题？

如何修复或避免RuntimeError？

Answer 1

您可以使用asyncio.async安排由create_connection返回由事件循环运行的协同程序，然后使用asyncio.Future的add_done_callback方法（更具体地说，asyncio.Task），其async返回到关闭一次循环的协同程序完成：

class EchoServer(asyncio.Protocol): 
    def connection_made(self, transport): 
     peername = transport.get_extra_info('peername') 
     self.transport = transport 

    def data_received(self, data): 
     loop = asyncio.get_event_loop() 
     coro = loop.create_connection(EchoClient, '127.0.0.1', 8890) 
     fut = asyncio.async(coro) 
     fut.add_done_callback(self.shutdown) 

    def shutdown(self, *args): 
     self.transport.close() 
     loop.stop()