Exception thrown in multiprocessing Pool not detected

Question

It seems that when an exception is raised from a multiprocessing.Pool process, there is no stack trace or any other indication that it has failed. Example:

Answer 1

I've had success logging exceptions with this decorator:

import traceback, functools, multiprocessing

def trace_unhandled_exceptions(func):
    @functools.wraps(func)
    def wrapped_func(*args, **kwargs):
        try:
            func(*args, **kwargs)
        except:
            print 'Exception in '+func.__name__
            traceback.print_exc()
    return wrapped_func

with the code in the question, it's

@trace_unhandled_exceptions
def go():
    print(1)
    raise Exception()
    print(2)

p = multiprocessing.Pool(1)

p.apply_async(go)
p.close()
p.join()

Simply decorate the function you pass to your process pool. The key to this working is @functools.wraps(func) otherwise multiprocessing throws a PicklingError.

code above gives

1
Exception in go
Traceback (most recent call last):
  File "", line 5, in wrapped_func
  File "", line 4, in go
Exception