python - 多处理子进程随机接收 SIGTERM

Question

我正在摆弄多处理和信号。我正在创建一个池，并让工作人员捕获 SIGTERM。没有明显的原因，我观察到子进程随机接收 SIGTERM 。这是一个 MWE:

import multiprocessing as mp
import signal
import os
import time

def start_process():
    print("Starting process #{}".format(os.getpid()))

def sigterm_handler(signo, _frame):
    print("Process #{} received a SIGTERM".format(os.getpid()))

def worker(i):
    time.sleep(1)

signal.signal(signal.SIGTERM, sigterm_handler)
while True:
    with mp.Pool(initializer=start_process) as pool:
        pool.map(worker, range(10))
    time.sleep(2)

输出:

Starting process #7735
Starting process #7736
Starting process #7737
Starting process #7738
Starting process #7739
Starting process #7740
Starting process #7741
Starting process #7742
Job done.
Starting process #7746
Starting process #7747
Starting process #7748
Starting process #7749
Starting process #7750
Starting process #7751
Starting process #7752
Starting process #7753
Process #7748 received a SIGTERM
Process #7746 received a SIGTERM
Job done.
Starting process #7757
Starting process #7758
Starting process #7759
Starting process #7760
Starting process #7761
Starting process #7762
Starting process #7763
Starting process #7764

如您所见，这看起来不可预测。

那么，这些 SIGTERM 来自哪里？这是正常的吗？我能保证 worker 完成他们的工作吗？最后，让子进程捕获 SIGTERM 可以吗？

Answer 1

这是正常现象，可能会在池执行时发生 __exit__离开上下文管理器时。由于 worker 们已经完成了他们的工作，所以没有什么可担心的。池本身会导致 SIGTERM对于没有可用退出代码的工作人员池检查它。这会在 Pool._terminate_pool 中触发-方法(Python 3.7.1):

    # Terminate workers which haven't already finished.
    if pool and hasattr(pool[0], 'terminate'):
        util.debug('terminating workers')
        for p in pool:
            if p.exitcode is None:
                p.terminate()

池工作人员将在几行后加入:

    if pool and hasattr(pool[0], 'terminate'):
        util.debug('joining pool workers')
        for p in pool:
            if p.is_alive():
                # worker has not yet exited
                util.debug('cleaning up worker %d' % p.pid)
                p.join()

在您调用 pool.terminate() 的场景中当你的员工明确地仍在运行(例如您正在使用 pool.map_async 然后使用 pool.terminate() )，您的应用程序将死锁等待 p.join() (除非你让 sigterm_handler 最终调用 sys.exit()) 。

如果没有必要，最好不要搞乱信号处理程序。