Question

我有一个模块，该模块可以阻止对某些TCP服务器的网络请求并接收响应。我必须将其集成到asyncio应用程序中。我的模块如下所示：

import socket

# class providing transport facilities
# can be implemented in any manner
# for example it can manage asyncio connection
class CustomTransport:
    def __init__(self, host, port):
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.host = host
        self.port = port

    def write(self, data):
        left = len(data)
        while left:
            written = self.sock.send(data.encode('utf-8'))
            left = left - written
            data = data[written:]

    def read(self, sz):
        return self.sock.recv(sz)

    def open(self):
        self.sock.connect((self.host, self.port))

    def close(self):
        self.sock.shutdown(2)


# generated. shouldn't be modified
# however any transport can be passed
class HelloNetClient:
    def __init__(self, transport):
        self.transport = transport

    def say_hello_net(self):
        self.transport.write('hello')
        response = self.transport.read(5)
        return response


# can be modified
class HelloService:
    def __init__(self):
        # create transport for connection to echo TCP server
        self.transport = CustomTransport('127.0.0.1', 6789)
        self.hello_client = HelloNetClient(self.transport)

    def say_hello(self):
        print('Saying hello...')
        return self.hello_client.say_hello_net()

    def __enter__(self):
        self.transport.open()
        return self

    def __exit__(self,exc_type, exc_val, exc_tb):
        self.transport.close()

用法：

def start_conversation():
    with HelloService() as hs:
        answer = hs.say_hello()
        print(answer.decode('utf-8'))


if __name__ == "__main__":
    start_conversation()

现在，我看到使模块与 asyncio 兼容的唯一方法是将所有内容转换为协程，并用asyncio提供的传输替换常规套接字。但是我不想触摸生成的代码（HelloNetClient）。有可能吗？

P.S。我希望这样使用它：

async def start_conversation():
    async with HelloService() as hs:
        answer = await hs.say_hello()
        print(answer.decode('utf-8'))


if __name__ == "__main__":
    loop = asyncio.get_event_loop()
    loop.run_until_complete(start_conversation())

Answer 1

HelloService可能需要使用run_in_executor（管理线程池）在后台运行HelloNetClient方法。例如：

async def say_hello(self):
    print('Saying hello...')
    loop = asyncio.get_event_loop()
    return await loop.run_in_executor(self.hello_client.say_hello_net)

这不是asyncio的惯用用法，并且您缺少其某些功能-例如，您将无法创建成千上万个并行工作的客户端，并且您将无法获得可靠的取消（能够cancel()完成您想要的任何任务）。尽管如此，简单的用法也可以。

不幸的是，此处提供自定义传输的功能没有帮助，因为中间层HelloNetClient期望同步行为。即使您要编写一个挂接到asyncio的自定义传输，say_hello_net之类的方法仍会等待，直到它需要响应才能到达，因此HelloService必须将它们安排在单独的时间中线。因此，最好的选择是使用默认传输方式，并将带有asyncio的代码与服务中的代码连接起来。

异步代码同步

1 个答案: