Python3 asyncio - 在自己的线程中运行两台服务器

Question

我的服务器类继承自 BaseServer:

class BaseServer(object):

    def __init__(self, host, port):
        self.loop = asyncio.new_event_loop()
        asyncio.set_event_loop(self.loop)

        self.instance = asyncio.start_server(self.handle_connection, host = host, port = port)

    async def handle_connection(self, reader: StreamReader, writer: StreamWriter):
        pass

    def start(self):
        # wrapping coroutine into ensure_future to allow it to call from call_soon
        # wrapping into lambda to make it callable
        callback = asyncio.ensure_future(self.instance)
        self.loop.call_soon(lambda: callback)
        self.loop.run_forever()
        self.loop.close()

    def stop(self):
        self.loop.call_soon_threadsafe(self.loop.stop)

    @staticmethod
    def get_instance():
        return BaseServer(None, None)

我需要两个在自己的线程中运行的服务器来并行处理请求。 但是当我尝试根据需要运行它们时，只有第一台服务器正在运行。下面是我如何运行它们：

if __name__ == '__main__':
    loop = asyncio.new_event_loop()
    asyncio.set_event_loop(loop)

    async def run():
        pool = ThreadPoolExecutor(max_workers=cpu_count())

        await loop.run_in_executor(pool, Server1.get_instance().start)
        await loop.run_in_executor(pool, Server2.get_instance().start)

    loop.run_until_complete(run())

1. 我做错了什么？如何在自己的线程中运行每个服务器？
2. 当asyncio.set_event_loop 从def __init__ 调用时，出现下一个错误：

RuntimeError: 线程 'Thread-1' 中没有当前事件循环。

但是如果我从def __init__ 中删除asyncio.set_event_loop 并将其移动到def start，错误就会消失。为什么会这样？

Answer 1

跟进 OP 的评论：

但是通过 run_until_complete 在同一个循环中运行两台服务器会阻止其中一台服务器循环处理对另一台服务器的请求，不是吗？如何正确运行两台服务器？

这里是 python 3.5 的 asyncio 文档中 TCP server example 的修改版本：

# Start server 1
coro1 = asyncio.start_server(handle_echo, '127.0.0.1', 8888, loop=loop)
server1 = loop.run_until_complete(coro1)
print('Serving 1 on {}'.format(server1.sockets[0].getsockname()))

# Start server 2
coro2 = asyncio.start_server(handle_echo, '127.0.0.1', 8889, loop=loop)
server2 = loop.run_until_complete(coro2)
print('Serving 2 on {}'.format(server2.sockets[0].getsockname()))

# Serve requests until Ctrl+C is pressed
try:
    loop.run_forever()
except KeyboardInterrupt:
    pass

# Close the servers
server1.close()
loop.run_until_complete(server1.wait_closed())
server2.close()
loop.run_until_complete(server2.wait_closed())

# Close the loop
loop.close()

请注意，在 asyncio 中添加了 python 3.7 后，它看起来像 much nicer：

async def main():
    server1 = await asyncio.start_server(
        handle_echo, '127.0.0.1', 8888)

    addr1 = server1.sockets[0].getsockname()
    print(f'Serving 1 on {addr1}')

    server2 = await asyncio.start_server(
        handle_echo, '127.0.0.1', 8889)

    addr2 = server2.sockets[0].getsockname()
    print(f'Serving 2 on {addr2}')

    async with server1, server2:
        await asyncio.gather(
            server1.serve_forever(), server2.serve_forever())

asyncio.run(main())