如何管理 Tornado 应用程序中资源的异步启动和关闭？

Question

我想在 Quart 或 FastAPI 中使用 aioredis in a Tornado application. However, I couldn't figure out a way to implement an async startup and shutdown of its resources since the Application class has no ASGI Lifespan 事件。换句话说，我需要在应用程序开始为请求提供服务之前创建一个 Redis 池，并在应用程序完成或即将结束后立即释放该池。问题是 aioredis 池创建是异步的，但 Tornado 应用程序创建是同步的。

基本应用程序如下所示：

    import os

from aioredis import create_redis_pool
from aioredis.commands import Redis
from tornado.httpserver import HTTPServer
from tornado.ioloop import IOLoop
from tornado.web import Application

from .handlers import hello

redis: Redis = None


async def start_resources() -> None:
    '''
    Initialize resources such as Redis and Database connections
    '''
    global redis
    REDIS_HOST = os.environ['REDIS_HOST']
    REDIS_PORT = os.environ['REDIS_PORT']
    redis = await create_redis_pool((REDIS_HOST, REDIS_PORT), encoding='utf-8')


async def close_resources() -> None:
    '''
    Release resources
    '''
    redis.close()
    await redis.wait_closed()


def create_app() -> Application:
    app = Application([
        ("/hello", hello.HelloHandler),
    ])

    return app


if __name__ == '__main__':

    app = create_app()
    http_server = HTTPServer(app)
    http_server.listen(8000)
    IOLoop.current().start()

重要的是我也可以在测试期间使用启动和关闭功能。

有什么想法吗？

Answer 1

要创建池，请在开始循环之前run_sync 调用协程：

if __name__ == '__main__': IOLoop.current().run_sync(start_resources) ...

要在程序退出前销毁池，请使用 try...finally 块，这样由于未处理的异常而导致的突然退出也被考虑在内：

if __name__ == '__main__': # create db pool IOLoop.current().run_sync(start_resources) ... try: # start the loop IOLoop.current().start() except: pass finally: # this will close the pool before exiting IOLoop.current().run_sync(close_resources)

Answer 2

是正确的，让我走上了正确的轨道。我只是认为它可以改进一点，所以我发布了这个替代方案：

from contextlib import contextmanager

# ... previous code omitted for brevity


@contextmanager
def create_app() -> Application:
    IOLoop.current().run_sync(start_resources)
    try:
        app = Application([
            ("/hello", hello.HelloHandler),
        ])
        yield app
    finally:
        IOLoop.current().run_sync(close_resources)


if __name__ == '__main__':
    with create_app() as app:
        http_server = HTTPServer(app)
        http_server.listen(8000)
        IOLoop.current().start()

此外，要在 pytest 和 pytest-tornado 的测试中使用此代码，您应该创建一个 conftest.py 文件，如下所示：

from typing import Iterator

from pytest import fixture
from tornado.platform.asyncio import AsyncIOLoop
from tornado.web import Application

from app.main import create_app


@fixture
def app(io_loop: AsyncIOLoop) -> Iterator[Application]:
    '''
    Return a Tornado.web.Application object with initialized resources
    '''
    with create_app() as app:
        yield app

请注意，将 io_loop 声明为依赖项注入很重要。

如何管理 Tornado 应用程序中资源的异步启动和关闭？

How do I manage asynchronous startup and shutdown of resources in a Tornado application?

shutdown

startup

tornado

python-asyncio

asgi