Django - 每隔x秒运行一次函数

Question

我正在使用Django应用。我有一个API端点，如果需要，它必须执行一个必须重复几次的函数（直到某个条件为真）。我现在如何处理它是 -

def shut_down(request):
  # Do some stuff
  while True:
    result = some_fn()
    if result:
      break
    time.sleep(2)

  return True

虽然我知道这是一种可怕的方法，而且我不应该在2秒内阻挡，但我无法弄清楚如何绕过它。
在等了4秒之后，这有效。但是我喜欢能让循环在后台运行的东西，并且一旦some_fn返回True就停止。 （另外，some_fn肯定会返回True）。

编辑 -
阅读Oz123的回复给了我一个似乎有用的想法。这就是我的所作所为 -

def shut_down(params):
    # Do some stuff
    # Offload the blocking job to a new thread

    t = threading.Thread(target=some_fn, args=(id, ), kwargs={})
    t.setDaemon(True)
    t.start()

    return True

def some_fn(id):
    while True:
        # Do the job, get result in res
        # If the job is done, return. Or sleep the thread for 2 seconds before trying again.

        if res:
            return
        else:
            time.sleep(2)

这对我有用。这很简单，但我不知道多线程与Django的结合效率如何。
如果有人能指出这方面的陷阱，那么批评就会受到赞赏。

Answer 1

对于许多小项目celery来说太过分了。对于那些您可以使用schedule的项目，它非常易于使用。

使用此库，您可以使任何函数定期执行任务：

import schedule
import time

def job():
    print("I'm working...")

schedule.every(10).minutes.do(job)
schedule.every().hour.do(job)
schedule.every().day.at("10:30").do(job)
schedule.every().monday.do(job)
schedule.every().wednesday.at("13:15").do(job)

while True:
    schedule.run_pending()
    time.sleep(1) 

该示例以阻塞方式运行，但是如果您查看常见问题解答，您会发现您还可以在并行线程中运行任务，这样您就不会阻塞，并且不再需要删除任务：< / p>

from schedule import Scheduler

def run_continuously(self, interval=1):
    """Continuously run, while executing pending jobs at each elapsed
    time interval.
    @return cease_continuous_run: threading.Event which can be set to
    cease continuous run.
    Please note that it is *intended behavior that run_continuously()
    does not run missed jobs*. For example, if you've registered a job
    that should run every minute and you set a continuous run interval
    of one hour then your job won't be run 60 times at each interval but
    only once.
    """

    cease_continuous_run = threading.Event()

    class ScheduleThread(threading.Thread):

        @classmethod
        def run(cls):
            while not cease_continuous_run.is_set():
                self.run_pending()
                time.sleep(interval)

    continuous_thread = ScheduleThread()
    continuous_thread.setDaemon(True)
    continuous_thread.start()
    return cease_continuous_run


Scheduler.run_continuously = run_continuously

以下是在类方法中使用的示例：

    def foo(self):
        ...
        if some_condition():
           return schedule.CancelJob  # a job can dequeue it

    # can be put in __enter__ or __init__
    self._job_stop = self.scheduler.run_continuously()

    logger.debug("doing foo"...)
    self.foo() # call foo
    self.scheduler.every(5).seconds.do(
        self.foo) # schedule foo for running every 5 seconds

    ...
    # later on foo is not needed any more:
    self._job_stop.set()

    ...

    def __exit__(self, exec_type, exc_value, traceback):
        # if the jobs are not stop, you can stop them
        self._job_stop.set()

Answer 2

此答案在Oz123's answer上有所扩展。

为了使事情顺利进行，我创建了一个名为mainapp/jobs.py的文件，其中包含计划的作业。然后，在我的apps.py模块中，将from . import jobs放在ready方法中。这是我的整个apps.py文件：

from django.apps import AppConfig
import os

class MainappConfig(AppConfig):
    name = 'mainapp'

    def ready(self):
        from . import jobs

        if os.environ.get('RUN_MAIN', None) != 'true':
            jobs.start_scheduler()

（RUN_MAIN检查是因为python manage.py runserver runs the ready method twice（在两个进程中每个都一次，但是我们只希望运行一次）。

现在，这是我放入jobs.py文件中的内容。一是进口。您需要如下导入Scheduler，threading和time。 F和UserHolding的导入恰好适合我的工作；您将不会导入这些。

from django.db.models import F
from schedule import Scheduler
import threading
import time

from .models import UserHolding

接下来，编写您要安排的功能。以下仅是示例；您的函数看起来不会像这样。

def give_admin_gold():
    admin_gold_holding = (UserHolding.objects
        .filter(inventory__user__username='admin', commodity__name='gold'))

    admin_gold_holding.update(amount=F('amount') + 1)

接下来，通过向schedule类添加run_continuously方法来对Scheduler模块进行猴子补丁。通过使用下面的代码来做到这一点，该代码是从Oz123的答案中逐字复制的。

def run_continuously(self, interval=1):
    """Continuously run, while executing pending jobs at each elapsed
    time interval.
    @return cease_continuous_run: threading.Event which can be set to
    cease continuous run.
    Please note that it is *intended behavior that run_continuously()
    does not run missed jobs*. For example, if you've registered a job
    that should run every minute and you set a continuous run interval
    of one hour then your job won't be run 60 times at each interval but
    only once.
    """

    cease_continuous_run = threading.Event()

    class ScheduleThread(threading.Thread):

        @classmethod
        def run(cls):
            while not cease_continuous_run.is_set():
                self.run_pending()
                time.sleep(interval)

    continuous_thread = ScheduleThread()
    continuous_thread.setDaemon(True)
    continuous_thread.start()
    return cease_continuous_run

Scheduler.run_continuously = run_continuously

最后，定义一个函数来创建一个Scheduler对象，连接您的工作，并调用调度程序的run_continuously方法。

def start_scheduler():
    scheduler = Scheduler()
    scheduler.every().second.do(give_admin_gold)
    scheduler.run_continuously()

Answer 3

我建议您使用Celery的task管理。您可以参考this设置此应用（包，如果您是从javaScript背景）。

设置完成后，您可以将代码更改为：

@app.task
def check_shut_down():
    if not some_fun():
        # add task that'll run again after 2 secs
        check_shut_down.delay((), countdown=3)
    else:
        # task completed; do something to notify yourself
        return True