如何优雅地处理SIGTERM信号? [英] How to process SIGTERM signal gracefully?

问题描述

假设我们有一个用python编写的琐碎的守护程序:

Let's assume we have such a trivial daemon written in python:

def mainloop():
    while True:
        # 1. do
        # 2. some
        # 3. important
        # 4. job
        # 5. sleep

mainloop()

，我们使用start-stop-daemon对其进行守护进程，默认情况下，它会在--stop上发送SIGTERM(TERM)信号.

and we daemonize it using start-stop-daemon which by default sends SIGTERM (TERM) signal on --stop.

让我们假设当前执行的步骤是#2.此时此刻，我们正在发送TERM信号.

Let's suppose the current step performed is #2. And at this very moment we're sending TERM signal.

发生的事情是执行立即终止.

What happens is that the execution terminates immediately.

我发现我可以使用signal.signal(signal.SIGTERM, handler)处理信号事件，但事实是它仍然会中断当前执行并将控制权传递给handler.

I've found that I can handle the signal event using signal.signal(signal.SIGTERM, handler) but the thing is that it still interrupts the current execution and passes the control to handler.

所以，我的问题是-是否可以不中断当前执行，而是在单独的线程(?)中处理TERM信号，以便我能够设置shutdown_flag = True以便使mainloop()有机会优雅地停下来?

So, my question is - is it possible to not interrupt the current execution but handle the TERM signal in a separated thread (?) so that I was able to set shutdown_flag = True so that mainloop() had a chance to stop gracefully?

推荐答案

基于类的全新使用解决方案:

A class based clean to use solution:

import signal
import time

class GracefulKiller:
  kill_now = False
  def __init__(self):
    signal.signal(signal.SIGINT, self.exit_gracefully)
    signal.signal(signal.SIGTERM, self.exit_gracefully)

  def exit_gracefully(self,signum, frame):
    self.kill_now = True

if __name__ == '__main__':
  killer = GracefulKiller()
  while not killer.kill_now:
    time.sleep(1)
    print("doing something in a loop ...")

  print("End of the program. I was killed gracefully :)")

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