Question

我需要运行一个动态的mapreduce作业，因为参数需要传递给地图，并在每次运行mapreduce作业时减少函数（例如，响应用户请求）。

我如何做到这一点？我无法在文档中看到如何在运行时为map和reduce进行动态处理。

class MatchProcessing(webapp2.RequestHandler):

  def get(self):
      requestKeyID=int(self.request.get('riderbeeRequestID'))
      userKey=self.request.get('userKey')
      pipeline = MatchingPipeline(requestKeyID, userKey)
      pipeline.start()
      self.redirect(pipeline.base_path + "/status?root=" + pipeline.pipeline_id)


class MatchingPipeline(base_handler.PipelineBase):
    def run(self, requestKeyID, userKey):
        yield mapreduce_pipeline.MapreducePipeline(
            "riderbee_matching",
            "tasks.matchingMR.riderbee_map",
            "tasks.matchingMR.riderbee_reduce",
            "mapreduce.input_readers.DatastoreInputReader",
            "mapreduce.output_writers.BlobstoreOutputWriter",
            mapper_params={
                "entity_kind": "models.rides.RiderbeeRequest",
                "requestKeyID": requestKeyID,
                "userKey": userKey,
            },
            reducer_params={
                "mime_type": "text/plain",
            },
            shards=16)


def riderbee_map(riderbeeRequest):
    # would like to access the requestKeyID and userKey parameters that were passed in mapper_params
    # so that we can do some processing based on that

    yield (riderbeeRequest.user.email, riderbeeRequest.key().id())


def riderbee_reduce(key, values):
    # would like to access the requestKeyID and userKey parameters that were passed earlier, perhaps through reducer_params
    # so that we can do some processing based on that

    yield "%s: %s\n" % (key, len(values))

请帮忙吗？

Answer 1

我很确定你可以在mapper_parameters中指定参数，并从上下文模块中读取它们。有关详细信息，请参阅http://code.google.com/p/appengine-mapreduce/wiki/UserGuidePython#Mapper_parameters。

Answer 2

这是使用上下文模块从mapper函数访问mapper参数的方法：

from mapreduce import context

def riderbee_map(riderbeeRequest):
    ctx = context.get()
    params = ctx.mapreduce_spec.mapper.params
    requestKeyID = params["requestKeyID"]

如何动态地将参数传递给GAE mapreduce上的映射函数？

2 个答案: