Spark不能腌制method_descriptor
问题内容：
我收到此奇怪的错误消息
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类型为元组的列表(key, (value1, value2))，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2个hbase函数，行和放置。当我评论它们时，两个代码都可以工作（将old_fi设置为空字典），但是如果其中一个运行，则会产生上述错误。我使用happybase在python中操作hbase。有人可以向我解释出什么问题吗？
问题答案：
Spark尝试序列化连接对象，以便可以在执行程序中使用，这肯定会失败，因为反序列化的db连接对象无法将读取/写入权限授予其他作用域（甚至计算机）。通过尝试广播连接对象可以重现该问题。对于这种情况，在序列化I
/ O对象时存在问题。
通过连接到map函数内部的数据库，部分解决了该问题。由于map函数中每个RDD元素的连接过多，因此我不得不切换到分区处理以将db连接从20k减少到大约8-64（基于分区的数量）。Spark开发人员应考虑为执行程序创建初始化函数/脚本，以避免出现此类死胡同问题。
假设我让每个节点都执行了此init函数，然后每个节点都将连接到数据库（某些conn池或单独的zookeeper节点），因为init函数和map函数将共享相同的作用域，然后出现问题不见了，所以您编写的代码比我发现的解决方法快。在执行结束时，spark将释放/卸载这些定义的变量，程序将结束。
