Question

我正在查询MongoDB以获取字典列表，对于列表中的每个字典，我正在对值进行一些比较。根据比较结果，我存储了字典，比较结果和mongoDB集合中计算的其他值的值。我试图通过调用多处理来实现这一点，并且收到此错误。

def save_for_doc(doc_id):

    #function to get the fields of doc
    fields = get_fields(doc_id)
    no_of_process = 5
    doc_col_size = 30000
    chunk_size = round(doc_col_size/no_of_process)
    chunk_ranges = range(0, no_of_process*chunk_size, chunk_size)
    processes = [ multiprocessing.Process(target=save_similar_docs, args= 
    (doc_id,client,fields,chunks,chunk_size)) for chunks in chunk_ranges]
    for prc in processes:
       prc.start()

def save_similar_docs(arguments):

     #This function process the args and saves the results to MongoDB. Does not 
     #return anything as the end result is directly stored.

以下是错误：

 File "H:/Desktop/Performance Improvement/With_Process_Pool.py", line 144, 
 in save_for_doc
   prc.start()

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\process.py", line 105, 
 in start
  self._popen = self._Popen(self)

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\context.py", line 223, 
 in _Popen
   return _default_context.get_context().Process._Popen(process_obj)

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\context.py", line 322, 
 in _Popen
   return Popen(process_obj)

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\popen_spawn_win32.py", 
 line 65, in __init__
reduction.dump(process_obj, to_child)

 File "C:\ProgramData\Anaconda3\lib\multiprocessing\reduction.py", line 60, 
 in dump
        ForkingPickler(file, protocol).dump(obj)

        TypeError: can't pickle _thread.lock objects

这个错误是什么意思？请解释一下，我该如何克服。

Answer 1

文档说您无法将客户端从主进程复制到子进程，您必须在fork之后创建连接。在分叉过程之后，无法复制客户端对象，创建连接。

在Unix系统上，多处理模块使用fork（）生成进程。使用带fork（）的MongoClient实例时必须小心。具体而言，不能将MongoClient的实例从父进程复制到子进程。相反，父进程和每个子进程必须创建自己的MongoClient实例。

http://api.mongodb.com/python/current/faq.html#id21

获取TypeError：无法挑选_thread.lock对象

1 个答案: