一段时间后杀死线程的大多数Python方法

Question

我想在线程中运行一个进程（正在对一个大的数据库表进行迭代）。在线程运行时，我只希望程序等待。如果该线程花费的时间超过30秒，我想终止该线程并执行其他操作。通过杀死线程，我的意思是我希望它停止活动并优雅地释放资源。

我想这样做是通过最好的方式Thread()的join(delay)和is_alive()功能，以及Event。使用join(delay)I，我可以让我的程序等待30秒等待线程完成，并且通过使用该is_alive()函数，我可以确定线程是否完成了工作。如果尚未完成工作，则设置事件，并且线程知道在该点停止工作。

这种方法有效吗，这是解决我的问题陈述的最有效的方法吗？

这是一些示例代码：

import threading
import time

# The worker loops for about 1 minute adding numbers to a set
# unless the event is set, at which point it breaks the loop and terminates
def worker(e):
    data = set()
    for i in range(60):
        data.add(i)
        if not e.isSet():
            print "foo"
            time.sleep(1)
        else:
            print "bar"
            break

e = threading.Event()
t = threading.Thread(target=worker, args=(e,))
t.start()

# wait 30 seconds for the thread to finish its work
t.join(30)
if t.is_alive():
    print "thread is not done, setting event to kill thread."
    e.set()
else:
    print "thread has already finished."

Answer 1

在这种情况下，使用事件作为信号传递机制就可以了，实际上在线程模块docs中建议使用。

如果您希望线程正常停止，请使其成为非守护进程，并使用适当的信号传递机制，例如Event。

验证线程终止时，超时几乎总是会引入错误空间。因此，虽然将.join()with超时用于触发事件的初始决策是可以的，但最终验证应使用.join()没有超时的a
进行。

# wait 30 seconds for the thread to finish its work
t.join(30)
if t.is_alive():
    print "thread is not done, setting event to kill thread."
    e.set()
    # The thread can still be running at this point. For example, if the 
    # thread's call to isSet() returns right before this call to set(), then
    # the thread will still perform the full 1 second sleep and the rest of 
    # the loop before finally stopping.
else:
    print "thread has already finished."

# Thread can still be alive at this point. Do another join without a timeout 
# to verify thread shutdown.
t.join()

可以简化为以下形式：

# Wait for at most 30 seconds for the thread to complete.
t.join(30)

# Always signal the event. Whether the thread has already finished or not, 
# the result will be the same.
e.set()

# Now join without a timeout knowing that the thread is either already 
# finished or will finish "soon."
t.join()