似乎在多进程处理中出现了两个让异常情况变得烦人的问题。首先(由 Glenn 指出),为了获得立即响应(即不用完成整个列表的处理),您需要使用带有超时的
map_async
,而不是
map
。其次(由 Andrey 指出),multiprocessing 无法捕获不继承自
Exception
的异常(例如
SystemExit
)。因此,这就是我的解决方案,可以同时解决这两个问题:
import sys
import functools
import traceback
import multiprocessing
def _poolFunctionWrapper(function, arg):
"""Run function under the pool
Wrapper around function to catch exceptions that don't inherit from
Exception (which aren't caught by multiprocessing, so that you end
up hitting the timeout).
"""
try:
return function(arg)
except:
cls, exc, tb = sys.exc_info()
if issubclass(cls, Exception):
raise
import traceback
print "Unhandled exception %s (%s):\n%s" % (cls.__name__, exc, traceback.format_exc())
raise Exception("Unhandled exception: %s (%s)" % (cls.__name__, exc))
def _runPool(pool, timeout, function, iterable):
"""Run the pool
Wrapper around pool.map_async, to handle timeout. This is required so as to
trigger an immediate interrupt on the KeyboardInterrupt (Ctrl-C); see
https://dev59.com/UnM_5IYBdhLWcg3wXx5N
Further wraps the function in _poolFunctionWrapper to catch exceptions
that don't inherit from Exception.
"""
return pool.map_async(functools.partial(_poolFunctionWrapper, function), iterable).get(timeout)
def myMap(function, iterable, numProcesses=1, timeout=9999):
"""Run the function on the iterable, optionally with multiprocessing"""
if numProcesses > 1:
pool = multiprocessing.Pool(processes=numProcesses, maxtasksperchild=1)
mapFunc = functools.partial(_runPool, pool, timeout)
else:
pool = None
mapFunc = map
results = mapFunc(function, iterable)
if pool is not None:
pool.close()
pool.join()
return results