Python 3 asyncio 如何正确关闭客户端连接

Question

我发现 tornado 网络应用程序存在内存泄漏，但我不确定如何修复它。经过一些内存分析后，我发现我的 memcached 客户端在关闭客户端连接时泄漏了字典。作为 auto-discovery mechanism w/ AWS ElastiCache 的一部分，我经常打开/关闭 memcached 客户端(具体来说每分钟一次) .

这是一个使用 pympler 的最小复制器演示泄漏:

from pympler import muppy, summary
import asyncio
import aiomcache

loop = asyncio.get_event_loop()

async def hello_aiomcache():
    mc = aiomcache.Client("127.0.0.1", 11211, loop=loop)
    await mc.set(b"some_key", b"Some value")
    value = await mc.get(b"some_key")
    print(value)
    values = await mc.multi_get(b"some_key", b"other_key")
    print(values)
    await mc.delete(b"another_key")
    mc.close()  

# establish a baseline (watch the <class 'dict line)
summary.print_(summary.summarize(muppy.get_objects()))

for i in range(50):
    loop.run_until_complete(hello_aiomcache())

# <class 'dict grows
summary.print_(summary.summarize(muppy.get_objects()))

ds = [ao for ao in muppy.get_objects() if isinstance(ao, dict)]

# leaked dict looks like {'_loop': <_UnixSelectorEventLoop running=False closed=False debug=False>, '_paused': False, '_drain_waiter': None, '_connection_lost': False, '_stream_reader': <StreamReader t=<_SelectorSocketTransport fd=34 read=polling write=<idle, bufsize=0>>>, '_stream_writer': None, '_client_connected_cb': None, '_over_ssl': False}
ds[2364]

看起来这些字典将永远存在，直到 loop.close() 被调用。我对此感到困惑。我认为我不想关闭我通过 tornado.ioloop.IOLoop.IOLoop.current().asyncio_loop 从 tornado 借来的循环。有没有其他方法可以在不关闭循环的情况下正确关闭/清理这些连接？

Answer 1

问题是由于 awaiting mc.close() 引起的。

我有点惊讶地发现协程在没有明确调度的情况下实际上不会运行。我天真地认为它最终会在未来的某个时候被调用。然而，coroutine docs明确声明:

Calling a coroutine does not start its code running – the coroutine object returned by the call doesn’t do anything until you schedule its execution. There are two basic ways to start it running: call await coroutine or yield from coroutine from another coroutine (assuming the other coroutine is already running!), or schedule its execution using the ensure_future() function or the AbstractEventLoop.create_task() method.