python - 异步客户端: `connection_lost` not called,导致ResourceWarning

我正在使用asyncio客户端进行连接，然后从服务器断开连接。

如果我连接到同一台计算机上的服务器程序，则连接会正常关闭。 添加:当我开始向连接写入数据时，该连接有时也开始发出警告。请参阅下面的第二个代码版本。

如果我连接到本地网络上的设备，则会得到ResourceWarning进行未封闭的传输。

如何正确关闭连接？

我在Windows 7(64位)上使用Python 3.6.0(32位)。

第一次尝试

相关代码:

import asyncio
import logging
import warnings

class ClientConnection(asyncio.Protocol):
    def connection_made(self, transport):
        self.transport = transport
        transport.write_eof()  # Send EOF to close connection

    def connection_lost(self, exception):
        self.transport.close()
        super().connection_lost(exception)

def main():
    logging.basicConfig(level=logging.DEBUG)
    eventLoop = asyncio.get_event_loop()
    eventLoop.set_debug(True)
    warnings.simplefilter('always', ResourceWarning)  # enables ResourceWarning
    #co = eventLoop.create_connection(ClientConnection, '127.0.0.1', 7001)     # Works without warning
    co = eventLoop.create_connection(ClientConnection, '192.168.10.66', 7001)  # Gives warning
    try:
        eventLoop.run_until_complete(co)
    finally:
        eventLoop.close()

if __name__ == "__main__":
    main()

控制台输出:

DEBUG:asyncio:Using selector: SelectSelector
DEBUG:asyncio:connect <socket.socket fd=240, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6> to ('19
2.168.10.66', 7001)
DEBUG:asyncio:poll took 0.000 ms: 1 events
DEBUG:asyncio:<socket.socket fd=240, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6, laddr=('192.168
.10.62', 64587), raddr=('192.168.10.66', 7001)> connected to 192.168.10.66:7001: (<_SelectorSocketTransport fd=240 read=
polling write=<idle, bufsize=0>>, <__main__.ClientConnection object at 0x005EBD90>)
DEBUG:asyncio:Close <_WindowsSelectorEventLoop running=False closed=False debug=True>
sys:1: ResourceWarning: unclosed <socket.socket fd=240, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto
=6, laddr=('192.168.10.62', 64587), raddr=('192.168.10.66', 7001)>
C:\Program Files (x86)\Python36-32\lib\asyncio\selector_events.py:631: ResourceWarning: unclosed transport <_SelectorSoc
ketTransport fd=240>
  source=self)

第二次尝试

我对代码进行了以下更改:

从transport.close()删除connection_lost

将一些数据写入连接

添加了data_received和eof_received回调

添加了更多调试日志

观察结果:

我尝试将transport.close()添加到connection_made中，但始终会导致OSError: [WinError 10038]。注意:这可能是另一个问题，所以让我们暂时忽略它，并假设我不会这样做。

将一些数据写入套接字时，本地主机连接也开始发出警告，但并不总是这样。

发出警告时，不会调用connection_lost。为什么？

修改后的代码:

import asyncio
import logging
import warnings

class ClientConnection(asyncio.Protocol):
    def connection_made(self, transport):
        logging.debug('connection_made')
        self.transport = transport
        transport.write(b'1234\r')
        transport.write_eof()  # Send EOF to close connection
        #transport.close()  # Cannot close here either, gives 'OSError: [WinError 10038]'

    def connection_lost(self, exception):
        logging.debug('connection_lost')
        super().connection_lost(exception)

    def data_received(self, data):
        logging.debug('received {} bytes'.format(len(data)))

    def eof_received(self):
        logging.debug('EOF received')
        self.transport.close()

def main():
    logging.basicConfig(level=logging.DEBUG)
    eventLoop = asyncio.get_event_loop()
    eventLoop.set_debug(True)
    warnings.simplefilter('always', ResourceWarning)  # enables ResourceWarning
    #co = eventLoop.create_connection(ClientConnection, '127.0.0.1', 7001)     # Works without warning
    co = eventLoop.create_connection(ClientConnection, '192.168.10.66', 7001)  # Gives warning
    try:
        eventLoop.run_until_complete(co)
        logging.debug('done')
    finally:
        eventLoop.close()

if __name__ == "__main__":
    main()

成功时输出:

...
DEBUG:root:EOF received
DEBUG:root:connection_lost
DEBUG:root:done
DEBUG:asyncio:Close <_WindowsSelectorEventLoop running=False closed=False debug=True>

失败时输出(请注意缺少connection_lost):

...
DEBUG:root:EOF received
DEBUG:root:done
DEBUG:asyncio:Close <_WindowsSelectorEventLoop running=False closed=False debug=True>
sys:1: ResourceWarning: unclosed <socket.socket fd=240, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto
=6, laddr=('127.0.0.1', 63858), raddr=('127.0.0.1', 7001)>
C:\Program Files (x86)\Python36-32\lib\asyncio\selector_events.py:631: ResourceWarning: unclosed transport <_SelectorSoc
ketTransport closing fd=240>
  source=self)

最佳答案

等待服务器关闭连接，或者使用transport.close()关闭传输。这也会触发connection_lost(不要从transport.close()调用connection_lost!):

class ClientConnection(asyncio.Protocol):
    def connection_made(self, transport):
        logging.debug("connection made, calling write eof")
        transport.write_eof()
        logging.debug("after calling write eof, calling close")
        transport.close()
        logging.debug("after calling close")

    def connection_lost(self, exception):
        logging.debug("connection lost")
        super().connection_lost(exception)

如果再尝试一些，您可能还会在本地计算机上得到一些ResourceWarning。例如，尝试在transport.write(b'hello world!')之前添加write_eof()或使本地服务器的响应速度变慢。

关于python - 异步客户端: `connection_lost` not called,导致ResourceWarning，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/41695498/