我喜欢zzzeek的回答。我只会用管道代替队列，因为如果多个线程/进程使用相同的管道端来生成日志消息，它们将被混淆。

下面是另一个简单的解决方案，适用于从谷歌到这里的其他人(比如我)。日志记录应该很简单!仅适用于3.2或更高版本。

import multiprocessing
import logging
from logging.handlers import QueueHandler, QueueListener
import time
import random


def f(i):
    time.sleep(random.uniform(.01, .05))
    logging.info('function called with {} in worker thread.'.format(i))
    time.sleep(random.uniform(.01, .05))
    return i


def worker_init(q):
    # all records from worker processes go to qh and then into q
    qh = QueueHandler(q)
    logger = logging.getLogger()
    logger.setLevel(logging.DEBUG)
    logger.addHandler(qh)


def logger_init():
    q = multiprocessing.Queue()
    # this is the handler for all log records
    handler = logging.StreamHandler()
    handler.setFormatter(logging.Formatter("%(levelname)s: %(asctime)s - %(process)s - %(message)s"))

    # ql gets records from the queue and sends them to the handler
    ql = QueueListener(q, handler)
    ql.start()

    logger = logging.getLogger()
    logger.setLevel(logging.DEBUG)
    # add the handler to the logger so records from this process are handled
    logger.addHandler(handler)

    return ql, q


def main():
    q_listener, q = logger_init()

    logging.info('hello from main thread')
    pool = multiprocessing.Pool(4, worker_init, [q])
    for result in pool.map(f, range(10)):
        pass
    pool.close()
    pool.join()
    q_listener.stop()

if __name__ == '__main__':
    main()

最简单的想法是:

获取当前进程的文件名和进程id。 设置一个[WatchedFileHandler][1]。这里将详细讨论此处理程序的原因，但简而言之，其他日志处理程序存在某些更糟糕的竞争条件。这个有最短的竞态条件窗口。 选择日志保存路径，例如“/var/log/…”

我刚刚写了一个我自己的日志处理程序，它只是通过管道将所有内容提供给父进程。我只测试了十分钟，但它似乎工作得很好。

(注意:这是硬编码到RotatingFileHandler，这是我自己的用例。)

更新:@javier现在将这种方法作为Pypi上可用的包来维护-参见Pypi上的multiprocessing-logging, github上的https://github.com/jruere/multiprocessing-logging

更新:实现!

现在它使用队列来正确地处理并发，并正确地从错误中恢复。现在，我已经在生产中使用了几个月了，下面的当前版本工作起来没有问题。

from logging.handlers import RotatingFileHandler
import multiprocessing, threading, logging, sys, traceback

class MultiProcessingLog(logging.Handler):
    def __init__(self, name, mode, maxsize, rotate):
        logging.Handler.__init__(self)

        self._handler = RotatingFileHandler(name, mode, maxsize, rotate)
        self.queue = multiprocessing.Queue(-1)

        t = threading.Thread(target=self.receive)
        t.daemon = True
        t.start()

    def setFormatter(self, fmt):
        logging.Handler.setFormatter(self, fmt)
        self._handler.setFormatter(fmt)

    def receive(self):
        while True:
            try:
                record = self.queue.get()
                self._handler.emit(record)
            except (KeyboardInterrupt, SystemExit):
                raise
            except EOFError:
                break
            except:
                traceback.print_exc(file=sys.stderr)

    def send(self, s):
        self.queue.put_nowait(s)

    def _format_record(self, record):
        # ensure that exc_info and args
        # have been stringified.  Removes any chance of
        # unpickleable things inside and possibly reduces
        # message size sent over the pipe
        if record.args:
            record.msg = record.msg % record.args
            record.args = None
        if record.exc_info:
            dummy = self.format(record)
            record.exc_info = None

        return record

    def emit(self, record):
        try:
            s = self._format_record(record)
            self.send(s)
        except (KeyboardInterrupt, SystemExit):
            raise
        except:
            self.handleError(record)

    def close(self):
        self._handler.close()
        logging.Handler.close(self)

下面是我简单的破解/变通方法…不是最全面的，但很容易修改，比我在写这篇文章之前找到的任何其他答案都更容易阅读和理解:

import logging
import multiprocessing

class FakeLogger(object):
    def __init__(self, q):
        self.q = q
    def info(self, item):
        self.q.put('INFO - {}'.format(item))
    def debug(self, item):
        self.q.put('DEBUG - {}'.format(item))
    def critical(self, item):
        self.q.put('CRITICAL - {}'.format(item))
    def warning(self, item):
        self.q.put('WARNING - {}'.format(item))

def some_other_func_that_gets_logger_and_logs(num):
    # notice the name get's discarded
    # of course you can easily add this to your FakeLogger class
    local_logger = logging.getLogger('local')
    local_logger.info('Hey I am logging this: {} and working on it to make this {}!'.format(num, num*2))
    local_logger.debug('hmm, something may need debugging here')
    return num*2

def func_to_parallelize(data_chunk):
    # unpack our args
    the_num, logger_q = data_chunk
    # since we're now in a new process, let's monkeypatch the logging module
    logging.getLogger = lambda name=None: FakeLogger(logger_q)
    # now do the actual work that happens to log stuff too
    new_num = some_other_func_that_gets_logger_and_logs(the_num)
    return (the_num, new_num)

if __name__ == '__main__':
    multiprocessing.freeze_support()
    m = multiprocessing.Manager()
    logger_q = m.Queue()
    # we have to pass our data to be parallel-processed
    # we also need to pass the Queue object so we can retrieve the logs
    parallelable_data = [(1, logger_q), (2, logger_q)]
    # set up a pool of processes so we can take advantage of multiple CPU cores
    pool_size = multiprocessing.cpu_count() * 2
    pool = multiprocessing.Pool(processes=pool_size, maxtasksperchild=4)
    worker_output = pool.map(func_to_parallelize, parallelable_data)
    pool.close() # no more tasks
    pool.join()  # wrap up current tasks
    # get the contents of our FakeLogger object
    while not logger_q.empty():
        print logger_q.get()
    print 'worker output contained: {}'.format(worker_output)

对于可能需要这个的人，我为multiprocessing_logging包写了一个装饰器，它将当前进程名添加到日志中，这样就可以清楚地看到谁记录了什么。

它还运行install_mp_handler()，因此在创建池之前运行它是没有用的。

这让我可以看到哪个工作人员创建了哪些日志消息。

下面是蓝图和示例:

import sys
import logging
from functools import wraps
import multiprocessing
import multiprocessing_logging

# Setup basic console logger as 'logger'
logger = logging.getLogger()
console_handler = logging.StreamHandler(sys.stdout)
console_handler.setFormatter(logging.Formatter(u'%(asctime)s :: %(levelname)s :: %(message)s'))
logger.setLevel(logging.DEBUG)
logger.addHandler(console_handler)


# Create a decorator for functions that are called via multiprocessing pools
def logs_mp_process_names(fn):
    class MultiProcessLogFilter(logging.Filter):
        def filter(self, record):
            try:
                process_name = multiprocessing.current_process().name
            except BaseException:
                process_name = __name__
            record.msg = f'{process_name} :: {record.msg}'
            return True

    multiprocessing_logging.install_mp_handler()
    f = MultiProcessLogFilter()

    # Wraps is needed here so apply / apply_async know the function name
    @wraps(fn)
    def wrapper(*args, **kwargs):
        logger.removeFilter(f)
        logger.addFilter(f)
        return fn(*args, **kwargs)

    return wrapper


# Create a test function and decorate it
@logs_mp_process_names
def test(argument):
    logger.info(f'test function called via: {argument}')


# You can also redefine undecored functions
def undecorated_function():
    logger.info('I am not decorated')


@logs_mp_process_names
def redecorated(*args, **kwargs):
    return undecorated_function(*args, **kwargs)


# Enjoy
if __name__ == '__main__':
    with multiprocessing.Pool() as mp_pool:
        # Also works with apply_async
        mp_pool.apply(test, ('mp pool',))
        mp_pool.apply(redecorated)
        logger.info('some main logs')
        test('main program')