mrjob 使用 mongoldb 数据源【转】

最近做的事情是用mrjob写mapreduce程序，从mongo读取数据。我的做法很容易也很好懂，因为mrjob可以支持sys.stdin的读取，所以我考虑用一个python程序读mongo中的数据，然后同时让mrjob脚本接受输入，处理，输出。

具体方式：

readInMongoDB.py:

#coding:UTF-8
‘‘‘
Created on 2014年5月28日

@author: hao
‘‘‘
import pymongo
pyconn = pymongo.Connection(host,port=27017)
pycursor = pyconn.userid_cid_score.find().batch_size(30)
for i in pycursor:
    userId = i[‘userId‘]
    cid = i[‘cid‘]
    score = i[‘score‘]
#     temp = list()
#     temp.append(userId)
#     temp.append(cid)
#     temp.append(score)
    print str(userId)+‘,‘+str(cid)+‘,‘+str(score)

step1.py:

#coding:UTF-8
‘‘‘
Created on 2014年5月27日

@author: hao
‘‘‘
from mrjob.job import MRJob
# from mrjob import protocol
import pymongo
import logging
import simplejson as sj

class step(MRJob):
    ‘‘‘
    ‘‘‘
#     logging.c
    def parseMatrix(self, _, line):
        ‘‘‘
        input one stdin for pymongo onetime search
        output contentId, (userId, rating)
        ‘‘‘
        line = (str(line))
        line=line.split(‘,‘)
        userId = line[0]
#         print userId
        cid = line[1]
#         print cid
        score = float(line[2])
#         print score
        yield cid, (userId, float(score))        

    def scoreCombine(self, cid, userRating):
        ‘‘‘
        将对同一个内容的（用户，评分）拼到一个list里
        ‘‘‘
        userRatings = list()
        for i in userRating:
            userRatings.append(i)
        yield cid, userRatings

    def userBehavior(self, cid, userRatings):
        ‘‘‘
        ‘‘‘
        scoreList = list()
        for doc in userRatings:
            # 每个combiner结果
            for i in doc:
                scoreList.append(i)
        for user1 in scoreList:
            for user2 in scoreList:
                if user1[0] == user2[0]:
                    continue
                yield (user1[0], user2[0]), (user1[1], user2[1])

    def steps(self):
        return [self.mr(mapper = self.parseMatrix,
                        reducer = self.scoreCombine),
                self.mr(reducer = self.userBehavior),]

if __name__==‘__main__‘:

    fp = open(‘a.txt‘,‘w‘)
    fp.write(‘[‘)
    step.run()
    fp.write(‘]‘)
    fp.close()

然后执行脚本  python readInMongoDB.py | python step1.py >> out.txt

这个方式在本地执行的非常好，没有任何问题（除开mrjob速度的问题，其实在本次应用中影响不大）

原文：http://blog.csdn.net/whzhcahzxh/article/details/29587059