python - 'Collection' object is not callable error in pymongo with process Pool

Question

使用下面的代码会导致:

'Collection' object is not callable. If you meant to call the '__getnewargs__' method on a 'Collection' object it is failing because no such method exists.

代码: 来自多处理导入池 db = MongoClient(ip,port)

def f(cursor, arg):
    for doc in cursor:
       ...

p = Pool(4)
for arg in args:
    cursor = db[dbName][collName].find()
    p.apply_async(f,[cursor, arg])

db.close()

无法弄清楚问题是什么以及如何调试代码。

完整回溯:

Exception in thread Thread-2:
Traceback (most recent call last):
  File "C:\Python27\lib\threading.py", line 808, in __bootstrap_inner
    self.run()
  File "C:\Python27\lib\threading.py", line 761, in run
    self.__target(*self.__args, **self.__kwargs)
  File "C:\Python27\lib\multiprocessing\pool.py", line 342, in _handle_tasks
    put(task)
  File "C:\Python27\lib\site-packages\pymongo\collection.py", line 1489, in __call__
    self.__name.split(".")[-1])
TypeError: 'Collection' object is not callable. If you meant to call the '__getnewargs__' method on a 'Collection' object it is failing because no such method exists.

Answer 1

您在使用 cursor 时遇到问题。Collection.find 方法返回一个 Cursor 对象，它是一个消耗品。 ( http://api.mongodb.org/python/current/api/pymongo/cursor.html#pymongo.cursor.Cursor.getitem ) 我不知道这是否是异常的原因，但这肯定是一个问题。

两种解决方案:

1. 在使用 [:] 或 list
线程之前明确提取文档
2. 在 apply_async 中提供光标并使用 clone 方法克隆光标 (http://api.mongodb.org/python/current/api/pymongo/cursor.html#pymongo.cursor.Cursor.clone)