python multiprocessing：某些函数完成后不返回（队列内容太大）

Question

我正在使用多处理的“进程和队列”。我并行启动了几个函数，大多数函数表现良好：它们完成了，它们的输出进入了Queue，它们显示为.is_alive（）==
False。但是由于某些原因，一些功能无法正常工作。即使函数的最后一行（显示“ Finished”的打印语句）完成，它们也始终显示.is_alive（）==
True。无论我启动的功能集是什么，都会发生这种情况，即使只有一个。如果不并行运行，则功能正常，并可以正常返回。什么 样的 事情可能是什么问题？

这是我用来管理作业的通用功能。我没有显示的只是传递给它的功能。它们很长，经常使用matplotlib，有时会启动一些shell命令，但是我无法弄清楚失败的命令的共同点。

def  runFunctionsInParallel(listOf_FuncAndArgLists):
    """
    Take a list of lists like [function, arg1, arg2, ...]. Run those functions in parallel, wait for them all to finish, and return the list of their return values, in order.   
    """
    from multiprocessing import Process, Queue

    def storeOutputFFF(fff,theArgs,que): #add a argument to function for assigning a queue
        print 'MULTIPROCESSING: Launching %s in parallel '%fff.func_name
        que.put(fff(*theArgs)) #we're putting return value into queue
        print 'MULTIPROCESSING: Finished %s in parallel! '%fff.func_name
        # We get this far even for "bad" functions
        return

    queues=[Queue() for fff in listOf_FuncAndArgLists] #create a queue object for each function
    jobs = [Process(target=storeOutputFFF,args=[funcArgs[0],funcArgs[1:],queues[iii]]) for iii,funcArgs in enumerate(listOf_FuncAndArgLists)]
    for job in jobs: job.start() # Launch them all
    import time
    from math import sqrt
    n=1
    while any([jj.is_alive() for jj in jobs]): # debugging section shows progress updates
        n+=1
        time.sleep(5+sqrt(n)) # Wait a while before next update. Slow down updates for really long runs.
        print('\n---------------------------------------------------\n'+ '\t'.join(['alive?','Job','exitcode','Func',])+ '\n---------------------------------------------------')
        print('\n'.join(['%s:\t%s:\t%s:\t%s'%(job.is_alive()*'Yes',job.name,job.exitcode,listOf_FuncAndArgLists[ii][0].func_name) for ii,job in enumerate(jobs)]))
        print('---------------------------------------------------\n')
    # I never get to the following line when one of the "bad" functions is running.
    for job in jobs: job.join() # Wait for them all to finish... Hm, Is this needed to get at the Queues?
    # And now, collect all the outputs:
    return([queue.get() for queue in queues])

Answer 1

好吧，当函数的输出太大时，似乎用来填充Queue的管道被塞住了（我的粗略理解？这是一个未解决/关闭的错误？http://bugs.python.org/issue8237）。我已经修改了问题中的代码，以便有一些缓冲（进程运行时会定期清空队列），这解决了我所有的问题。因此，现在需要执行任务（函数及其参数）的集合，启动它们并收集输出。我希望它看起来更简单/更干净。

编辑（2014年9月；
2017年11月更新：为了可读性而重写）：我正在使用自那时以来所做的增强功能更新代码。新代码（功能相同，但功能更好）在此处：https
:
//gitlab.com/cpbl/cpblUtilities/blob/master/parallel.py

调用说明也在下面。

def runFunctionsInParallel(*args, **kwargs):
    """ This is the main/only interface to class cRunFunctionsInParallel. See its documentation for arguments.
    """
    return cRunFunctionsInParallel(*args, **kwargs).launch_jobs()

###########################################################################################
###
class cRunFunctionsInParallel():
    ###
    #######################################################################################
    """Run any list of functions, each with any arguments and keyword-arguments, in parallel.
The functions/jobs should return (if anything) pickleable results. In order to avoid processes getting stuck due to the output queues overflowing, the queues are regularly collected and emptied.
You can now pass os.system or etc to this as the function, in order to parallelize at the OS level, with no need for a wrapper: I made use of hasattr(builtinfunction,'func_name') to check for a name.
Parameters
----------
listOf_FuncAndArgLists : a list of lists 
    List of up-to-three-element-lists, like [function, args, kwargs],
    specifying the set of functions to be launched in parallel.  If an
    element is just a function, rather than a list, then it is assumed
    to have no arguments or keyword arguments. Thus, possible formats
    for elements of the outer list are:
      function
      [function, list]
      [function, list, dict]
kwargs: dict
    One can also supply the kwargs once, for all jobs (or for those
    without their own non-empty kwargs specified in the list)
names: an optional list of names to identify the processes.
    If omitted, the function name is used, so if all the functions are
    the same (ie merely with different arguments), then they would be
    named indistinguishably
offsetsSeconds: int or list of ints
    delay some functions' start times
expectNonzeroExit: True/False
    Normal behaviour is to not proceed if any function exits with a
    failed exit code. This can be used to override this behaviour.
parallel: True/False
    Whenever the list of functions is longer than one, functions will
    be run in parallel unless this parameter is passed as False
maxAtOnce: int
    If nonzero, this limits how many jobs will be allowed to run at
    once.  By default, this is set according to how many processors
    the hardware has available.
showFinished : int
    Specifies the maximum number of successfully finished jobs to show
    in the text interface (before the last report, which should always
    show them all).
Returns
-------
Returns a tuple of (return codes, return values), each a list in order of the jobs provided.
Issues
-------
Only tested on POSIX OSes.
Examples
--------
See the testParallel() method in this module
    """