Python Quart无法关闭后台任务

Question

我正在开发一个Python应用程序，但我正在从Flask移动到Quart。应用程序需要一个在应用程序运行时持续运行的后台任务。

当我尝试使用control-c停止该进程时，线程并没有干净地关闭，而是处于shutdown例程中的while循环中。

    while not self._master_thread_class.shutdown_completed:
        if not pro:
            print('[DEBUG] Thread is not complete')
            pro = True

我已经跟踪了this堆栈溢出问题，但我不知道如何干净利落地关闭后台线程，所以我想要一个解释，因为它看起来夸特文档有点缺乏。

MasterThread类：

import asyncio

class MasterThread:

    def __init__(self, shutdown_requested_event):
        self._shutdown_completed = False
        self._shutdown_requested_event = shutdown_requested_event
        self._shutdown_requested = False

    def __del__(self):
        print('Thread was deleted')

    def run(self, loop) -> None:
        asyncio.set_event_loop(loop)
        loop.run_until_complete(self._async_entrypoint())

    @asyncio.coroutine
    def _async_entrypoint(self) -> None:
        while not self. _shutdown_requested and \
            not self._shutdown_requested_event.isSet():
            #print('_main_loop()')
            pass

            if self._shutdown_requested_event.wait(0.1):
                self. _shutdown_requested = True

        print('[DEBUG] thread has completed....')
        self._shutdown_completed = True

    def _main_loop(self) -> None:
        print('_main_loop()')

主要应用模块：

import asyncio
import threading
from quart import Quart
from workthr import MasterThread

app = Quart(__name__)

class Service:

    def __init__(self):
        self._shutdown_thread_event = threading.Event()
        self._master_thread = MasterThread(self._shutdown_thread_event)
        self._thread = None

    def __del__(self):
        self.stop()

    def start(self):
        loop = asyncio.get_event_loop()
        self._thread = threading.Thread(target=self._master_thread.run, args=(loop,))
        self._thread.start()
        return True

    def stop(self) -> None:
        print('[DEBUG] Stop signal caught...')
        self._shutdown_thread_event.set()
        while not self._master_thread.shutdown_completed:
            print('[DEBUG] Thread is not complete')

        print('[DEBUG] Thread has completed')

        self._shutdown()

    def _shutdown(self):
        print('Shutting down...')

service = Service()
service.start()

Answer 1

Quart有一些startup and shutdown方法，允许在服务器开始服务之前启动一些东西，并在服务器结束服务时停止。如果你的后台任务主要是IO限制的，我建议你只使用协程函数而不是线程，

async def background_task():
    while True:
        ...

@app.before_serving
async def startup():
    app.background_task = asyncio.ensure_future(background_task())

@app.after_serving
async def shutdown():
    app.background_task.cancel()  # Or use a variable in the while loop

或者您也可以对您的服务执行相同的操作，

@app.before_serving
async def startup():
    service.start()

@app.after_serving
async def shutdown():
    service.stop()