如何停止多处理.池出现异常

Question

在下面的代码中，我在第一次调用时引发了一个异常，但这个异常似乎被吸收了，而且我仍然执行了所有其他进程，这是怎么回事？我想要的是，每当出现第一个异常时，打印它，并直接停止多处理池。

def func(i):
if i==0:
raise Exception()
else:
time.sleep(1)
print(i)
num_workers = 4
pool = multiprocessing.Pool(num_workers)
try:
for i in range(4):
pool.apply_async(func,args=(i,))
except:
print("err")
pool.close()
pool.join()

以下根据HTF 编辑的代码

import multiprocessing
import time
if __name__ == '__main__':
def func(i):
if i == 0:
raise Exception()
else:
time.sleep(1)
print(i)

num_workers = 4
pool = multiprocessing.Pool(num_workers)
results = [pool.apply_async(func, args=(i,)) for i in range(4)]
try:
for result in results:
result.get()
except:
print("err")
pool.close()
pool.join()

给出输出

err
1
2
3

我只期望err

Answer 1

您刚刚安排了任务，但需要等待结果：

results = [pool.apply_async(func,args=(i,)) for i in range(4)]
try:
for result in results:
result.get()
except:
print("err")

更新时间：2021年4月7日星期三20:42:59 UTC：

你可以试试这样的东西：

import time

from functools import partial
from multiprocessing import Pool

def func(i):
if i == 0:
raise Exception("something bad happened")
else:
time.sleep(1)
print(i)

def quit(pool, err):
print(f"ERROR: {err}")
pool.terminate()

def main():
pool = Pool()
partial_quit = partial(quit, pool)
for i in range(4):
pool.apply_async(func, args=(i,), error_callback=partial_quit)
pool.close()
pool.join()

if __name__ == "__main__":
main()

测试：

$ python test1.py
ERROR: something bad happened

如果您需要返回值，那么使用裸进程和队列实际上可能更容易：

import time

from multiprocessing import Process, Queue
PROCS = 4

def worker(q, i):
if i == 10:
print("error")
q.put_nowait("ERROR")
else:
time.sleep(1)
print(i)
q.put_nowait(i)

def main():
q = Queue()
procs = []
for i in range(PROCS):
p = Process(target=worker, args=(q, i))
p.start()
procs.append(p)
count = len(procs)
while count:
result = q.get()
if result == "ERROR":
for p in procs:
p.terminate()
break
print(f"Result for: {result}")
count -= 1

if __name__ == "__main__":
main()

测试：

$ python test2.py
0
2
1
3
Result for: 0
Result for: 2
Result for: 1
Result for: 3