返回空上下文的Google python map-reduce库
class DeleteOldObservationsMapper(object):
"""Mapper for deleting old observations."""
def __init__(self):
logging.info('DeleteOldObservationsMapper init')
ctx = mapreduce.context.get()
when = ctx.mapreduce_spec.mapper.params.get('before_timestamp_seconds')
assert when
self.before_datetime = datetime.datetime.utcfromtimestamp(when)
logging.info('before_datetime %s', self.before_datetime)以下是错误跟踪：
ERROR 2013-05-24 16:03:38,662 webapp2.py:1552] 'NoneType' object has no attribute
'mapreduce_spec'
Traceback (most recent call last):
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1535, in __call__
rv = self.handle_exception(request, response, e)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1529, in __call__
rv = self.router.dispatch(request, response)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher
return route.handler_adapter(request, response)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1102, in __call__
return handler.dispatch()
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 572, in dispatch
return self.handle_exception(e, self.app.debug)
File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 570, in dispatch
return method(*args, **kwargs)
File "/Users/leoromanovsky/code/adapt/server/mapreduce/base_handler.py", line 66, in post
self.handle()
File "/Users/leoromanovsky/code/adapt/server/mapreduce/handlers.py", line 320, in handle
tstate = model.TransientShardState.from_request(self.request)
File "/Users/leoromanovsky/code/adapt/server/mapreduce/model.py", line 993, in from_request
handler = mapreduce_spec.mapper.handler
File "/Users/leoromanovsky/code/adapt/server/mapreduce/model.py", line 618, in get_handler
return util.handler_for_name(self.handler_spec)
File "/Users/leoromanovsky/code/adapt/server/mapreduce/util.py", line 149, in handler_for_name
return getattr(resolved_name.im_class(), resolved_name.__name__)
File "/Users/leoromanovsky/code/adapt/server/jobs.py", line 22, in __init__
when = ctx.mapreduce_spec.mapper.params.get('before_timestamp_seconds')
AttributeError: 'NoneType' object has no attribute 'mapreduce_spec'回答 2
Stack Overflow用户
发布于 2013-11-29 02:53:16
我们最近在一个threadsafe: false项目中遇到了这个问题，并且能够通过改变导入context模块的方式来解决这个问题。凯文在this bug report中很好地解释了这个问题。
kevin.mo...@gmail.com也许这会对其他人有所帮助，但我看到了这个问题，并为我的用例解决了这个问题。在我们的项目中，mapreduce库位于子文件夹"libs/external/mapreduce“中，而不是项目的根目录。
该库将上下文(以及其他内容)作为from mapreduce import context从自身导入。因此，为了让它工作，我们使用导入操作，如下所示：
导入os，sys sys.path.append(os.path.join(os.path.dirname(__file__)，‘libs/external’)
然而，在我们代码中的一些地方，我们仍然像这样导入上下文：
从libs.external.mapreduce导入上下文
这实际上会导致context被导入两次，mapreduce.context.Context._local将被设置两次，从而拥有两个不同的thread._local实例。当调用Context._set以在映射器函数中存储上下文以供以后检索时，它将使用原始的thread._local实例。
稍后，当我们的映射器模块再次导入上下文时，它将获得一个新的thread._local实例。当我们使用calling context.get()时，它返回的是实际上没有上下文的新实例：
AttributeError：“NoneType”对象没有特性“”mapreduce_spec“”
将我们所有的导入切换到from mapreduce import context为我们解决了这个问题。
Stack Overflow用户
发布于 2013-07-02 04:40:08
我想这就是你的问题的答案：
http://code.google.com/p/appengine-mapreduce/issues/detail?id=127
mapreduce.context.get()根本不是线程保存...
所以你可以做的就是把它打包到一个包装器中，使它成为线程保存，然后使用Lock机制。
https://stackoverflow.com/questions/16739802
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