火花不能腌制method_descriptor

Question

我收到一条奇怪的错误信息

15/01/26 13:05:12 INFO spark.SparkContext: Created broadcast 0 from wholeTextFiles at NativeMethodAccessorImpl.java:-2
Traceback (most recent call last):
  File "/home/user/inverted-index.py", line 78, in <module>
    print sc.wholeTextFiles(data_dir).flatMap(update).top(10)#groupByKey().map(store)
  File "/home/user/spark2/python/pyspark/rdd.py", line 1045, in top
    return self.mapPartitions(topIterator).reduce(merge)
  File "/home/user/spark2/python/pyspark/rdd.py", line 715, in reduce
    vals = self.mapPartitions(func).collect()
  File "/home/user/spark2/python/pyspark/rdd.py", line 676, in collect
    bytesInJava = self._jrdd.collect().iterator()
  File "/home/user/spark2/python/pyspark/rdd.py", line 2107, in _jrdd
    pickled_command = ser.dumps(command)
  File "/home/user/spark2/python/pyspark/serializers.py", line 402, in dumps
    return cloudpickle.dumps(obj, 2)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 816, in dumps
    cp.dump(obj)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 133, in dump
    return pickle.Pickler.dump(self, obj)
  File "/usr/lib/python2.7/pickle.py", line 224, in dump
    self.save(obj)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 562, in save_tuple
    save(element)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 254, in save_function
    self.save_function_tuple(obj, [themodule])
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 304, in save_function_tuple
    save((code, closure, base_globals))
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 548, in save_tuple
    save(element)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 600, in save_list
    self._batch_appends(iter(obj))
  File "/usr/lib/python2.7/pickle.py", line 633, in _batch_appends
    save(x)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 254, in save_function
    self.save_function_tuple(obj, [themodule])
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 304, in save_function_tuple
    save((code, closure, base_globals))
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 548, in save_tuple
    save(element)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 600, in save_list
    self._batch_appends(iter(obj))
  File "/usr/lib/python2.7/pickle.py", line 633, in _batch_appends
    save(x)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 254, in save_function
    self.save_function_tuple(obj, [themodule])
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 304, in save_function_tuple
    save((code, closure, base_globals))
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 548, in save_tuple
    save(element)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 600, in save_list
    self._batch_appends(iter(obj))
  File "/usr/lib/python2.7/pickle.py", line 636, in _batch_appends
    save(tmp[0])
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 249, in save_function
    self.save_function_tuple(obj, modList)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 309, in save_function_tuple
    save(f_globals)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 174, in save_dict
    pickle.Pickler.save_dict(self, obj)
  File "/usr/lib/python2.7/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.7/pickle.py", line 681, in _batch_setitems
    save(v)
  File "/usr/lib/python2.7/pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 650, in save_reduce
    save(state)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 174, in save_dict
    pickle.Pickler.save_dict(self, obj)
  File "/usr/lib/python2.7/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.7/pickle.py", line 681, in _batch_setitems
    save(v)
  File "/usr/lib/python2.7/pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 650, in save_reduce
    save(state)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 174, in save_dict
    pickle.Pickler.save_dict(self, obj)
  File "/usr/lib/python2.7/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.7/pickle.py", line 681, in _batch_setitems
    save(v)
  File "/usr/lib/python2.7/pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 650, in save_reduce
    save(state)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 174, in save_dict
    pickle.Pickler.save_dict(self, obj)
  File "/usr/lib/python2.7/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.7/pickle.py", line 681, in _batch_setitems
    save(v)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 547, in save_inst
    self.save_inst_logic(obj)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 537, in save_inst_logic
    save(stuff)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 174, in save_dict
    pickle.Pickler.save_dict(self, obj)
  File "/usr/lib/python2.7/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.7/pickle.py", line 681, in _batch_setitems
    save(v)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 547, in save_inst
    self.save_inst_logic(obj)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 537, in save_inst_logic
    save(stuff)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 174, in save_dict
    pickle.Pickler.save_dict(self, obj)
  File "/usr/lib/python2.7/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.7/pickle.py", line 681, in _batch_setitems
    save(v)
  File "/usr/lib/python2.7/pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 616, in save_reduce
    save(cls)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 467, in save_global
    d),obj=obj)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 631, in save_reduce
    save(args)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib/python2.7/pickle.py", line 548, in save_tuple
    save(element)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 174, in save_dict
    pickle.Pickler.save_dict(self, obj)
  File "/usr/lib/python2.7/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib/python2.7/pickle.py", line 681, in _batch_setitems
    save(v)
  File "/usr/lib/python2.7/pickle.py", line 331, in save
    self.save_reduce(obj=obj, *rv)
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 616, in save_reduce
    save(cls)
  File "/usr/lib/python2.7/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/home/user/spark2/python/pyspark/cloudpickle.py", line 442, in save_global
    raise pickle.PicklingError("Can't pickle builtin %s" % obj)
pickle.PicklingError: Can't pickle builtin <type 'method_descriptor'>

我的更新函数返回一个(key, (value1, value2))类型的元组列表，它们都是字符串，如下所示：

def update(doc):
    doc_id  = doc[0][path_len:-ext_len] #actual file name
    content = doc[1].lower()

    new_fi = regex.split(content)
    old_fi = fi_table.row(doc_id)

    fi_table.put(doc_id, {'cf:col': ",".join(new_fi)})

    if not old_fi:
        return [(term, ('add', doc_id)) for term in new_fi]
    else:
        new_fi = set(new_fi)
        old_fi = set(old_fi['cf:col'].split(','))
        return [(term, ('add', doc_id)) for term in new_fi - old_fi] + \
               [(term, ('del', doc_id)) for term in old_fi - new_fi]

编辑：问题在于这两个hbase函数、行和put。当我对它们进行注释时，这两种代码都可以工作(将old_fi设置为一个空字典)，但如果其中一个运行，则会产生上述错误。我在python中使用粒子基来操作hbase。有人能解释我出了什么问题吗？

Answer 1

Spark试图序列化connect对象，以便它可以在执行器中使用，这肯定会失败，因为反序列化的db connect对象不能将读/写权限授予另一个范围(甚至计算机)。这个问题可以通过广播connect对象来再现。对于这个实例，序列化i/o对象时出现了问题。

通过连接到地图函数中的数据库，部分解决了这个问题。由于map函数中的每个RDD元素都有太多的连接，所以我不得不切换到分区处理，以便将db连接从20k减少到大约8-64个(基于分区的数量)。Spark开发人员应该考虑为执行器创建一个初始化函数/脚本，以避免这种死胡同问题。

假设我让每个节点执行这个init函数，那么每个节点都将连接到数据库(一些conn池，或者单独的zookeeper节点)，因为init函数和map函数将共享相同的作用域，然后问题就消失了，所以您编写的代码比我找到的解决方案要快。在执行结束时，火花将释放/卸载这些定义的变量，程序将结束。

Answer 2

如果这确实是MethodDescriptorType的泡菜问题，您可以注册如何对MethodDescriptorType进行腌制，如下所示：

def _getattr(objclass, name, repr_str):
    # hack to grab the reference directly
    try:
        attr = repr_str.split("'")[3]
        return eval(attr+'.__dict__["'+name+'"]')
    except:
        attr = getattr(objclass,name)
        if name == '__dict__':
            attr = attr[name]
        return attar


def save_wrapper_descriptor(pickler, obj):
    pickler = Pickler(file, protocol)
    pickler.save_reduce(_getattr, (obj.__objclass__, obj.__name__,
                                   obj.__repr__()), obj=obj)
    return

# register the following "type" with:
#     Pickler.dispatch[MethodDescriptorType] = save_wrapper_descriptor
MethodDescriptorType = type(type.__dict__['mro'])

然后，如果将上面的内容注册到spark使用的酸洗调度表(如上面所示，或使用copy_reg)，则可能会避免酸洗错误。