将作业提交到异步事件循环

Question

我想将作业从线程提交到 asyncio 事件循环（就像 run_in_executor 但相反）。

asyncio 文档对 concurrency and multithreading 的描述如下：

To schedule a callback from a different thread, the BaseEventLoop.call_soon_threadsafe() method should be used. Example to schedule a coroutine from a different thread: loop.call_soon_threadsafe(asyncio.async, coro_func())

这很好用，但协程的结果丢失了。

相反，可以使用向 async（或 ensure_future）返回的未来添加完成回调的函数，以便线程可以通过 concurrent.futures.Future.

标准库中没有实现这样的功能是否有特殊原因？还是我错过了更简单的方法？

Answer 1

我的请求得到了满足 run_coroutine_threadsafe function has been implemented here。

示例：

def target(loop, timeout=None):
    future = asyncio.run_coroutine_threadsafe(add(1, b=2), loop)
    return future.result(timeout)

async def add(a, b):
    await asyncio.sleep(1)
    return a + b

loop = asyncio.get_event_loop()
future = loop.run_in_executor(None, target, loop)
assert loop.run_until_complete(future) == 3

我最初发布了 concurrent.futures.Executor 的子 class 仍然可以实现为：

class LoopExecutor(concurrent.futures.Executor):
    """An Executor subclass that uses an event loop 
    to execute calls asynchronously."""

    def __init__(self, loop=None):
        """Initialize the executor with a given loop."""
        self.loop = loop or asyncio.get_event_loop()

    def submit(self, fn, *args, **kwargs):
        """Schedule the callable, fn, to be executed as fn(*args **kwargs).
        Return a Future object representing the execution of the callable."""
        coro = asyncio.coroutine(fn)(*args, **kwargs)
        return asyncio.run_coroutine_threadsafe(coro, self.loop)

将作业提交到异步事件循环

Submit a job to an asyncio event loop

python

multithreading

python-asyncio