MapReduce

化繁为简 如何向老婆解释MapReduce?

狂风中的少年 提交于 2019-12-26 17:11:03
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>>   昨天,我在Xebia印度办公室发表了一个关于MapReduce的演说。演说进行得很顺利,听众们都能够理解MapReduce的概念(根据他们的反馈)。我成功地向技术听众们(主要是Java程序员,一些Flex程序员和少数的测试员)解释了MapReduce的概念,这让我感到兴奋。在所有辛勤的工作之后,我们在Xebia印度办公室享用了丰盛的晚餐,然后我径直回了家。   回家后,我的妻子(Supriya)问道:“你的会开得怎么样?”我说还不错。 接着她又问我会议是的内容是什么(她不是从事软件或编程领域的工作的)。我告诉她说MapReduce。“Mapduce,那是什么玩意儿?”她问道: “跟地形图有关吗?”我说不,不是的,它和地形图一点关系也没有。“那么,它到底是什么玩意儿?”妻子问道。 “唔…让我们去Dominos(披萨连锁)吧,我会在餐桌上跟你好好解释。” 妻子说:“好的。” 然后我们就去了披萨店。 MapReduce工作原理示意图(图片来自jobbole)   我们在Domions点餐之后,柜台的小伙子告诉我们说披萨需要15分钟才能准备好。于是,我问妻子:“你真的想要弄懂什么是MapReduce?” 她很坚定的回答说“是的”。 因此我问道:   我: 你是如何准备洋葱辣椒酱的?(以下并非准确食谱,请勿在家尝试)

Compiling hadoop java files

≡放荡痞女 提交于 2019-12-26 06:50:06
问题 I need to compile Java Hadoop programs. I have compiled and got .class files for mapper and reducer. But when I compile mainjava file, i keep getting this error. that is it can't point mapper and reducer class files. How can I resolve this issue? 回答1: You have to give all of your source files to javac Example: javac -classpath /usr/local/hadoop/hadoop-core-1.0.4.jar -sourcepath src/ -d build/ MyMain.java MyMapper.java MyReducer.java 回答2: hadoop-core-${VERSION}.jar is in ${HADOOP_HOME}/share

Compiling hadoop java files

淺唱寂寞╮ 提交于 2019-12-26 06:49:09
问题 I need to compile Java Hadoop programs. I have compiled and got .class files for mapper and reducer. But when I compile mainjava file, i keep getting this error. that is it can't point mapper and reducer class files. How can I resolve this issue? 回答1: You have to give all of your source files to javac Example: javac -classpath /usr/local/hadoop/hadoop-core-1.0.4.jar -sourcepath src/ -d build/ MyMain.java MyMapper.java MyReducer.java 回答2: hadoop-core-${VERSION}.jar is in ${HADOOP_HOME}/share

Hadoop阅读笔记(一)——强大的MapReduce

天大地大妈咪最大 提交于 2019-12-26 02:42:27
前言: 来园子已经有8个月了,当初入园凭着满腔热血和一脑门子冲动,给自己起了个响亮的旗号“大数据 小世界”,顿时有了种世界都是我的,世界都在我手中的赶脚。可是......时光飞逝,岁月如梭~~~随手一翻自己的博客,可视化已经快占据了半壁江山,思来想去,还是觉得把一直挂在嘴头,放在心头的大数据拿出来说说,哦不,是拿过来学学。入园前期写了有关 Nutch 和 Solr 的自己的一些阅读体会和一些尝试,挂着大数据的旗号做着爬虫的买卖。可是,时间在流失,对于大数据的憧憬从未改变,尤其是Hadoop一直让我魂牵梦绕,打今儿起,开始着手自己的大数据系列,把别人挤牙膏的时间用在学习上,收拾好时间,收拾好资料,收拾好自己,重返Hadoop。 以下是对于大数据学习的一种预期规划: 主要理论指导材料:Hadoop实战2 主要手段:敲代码、结合API理解 预期目标:深入了解Hadoop,能为我所用 正文: 记得去年还在学校写小论文的时候,我花了一天的时间,懵懵懂懂的把Hadoop的环境给打起来了,今年出来接触社会,由于各种原因,自己又搭了几次伪分布式的环境,每次想学习Hadoop的心态好比每次背单词,只要一背单词,总是又从“abandon”开始背起。所以环境这块就不多说了,网上这样的帖子早已烂大街(因为Hadoop版本更新很快,目前应该是到2.6版本了,所以博文肯定一直在推陈出新)。用的Ubuntu12

Read from reducer output file

若如初见. 提交于 2019-12-25 18:26:41
问题 I have some MapReduce job and I would like to use the output file of Reducer further in Java code. How can I read from such a file, since it's on distributed file system? Thanks 回答1: Since you want to use output file of Reducer further in a simple java code, for that you can use the following code:- ` try{ Path pt=new Path("hdfs://npvm11.np.wc1.yellowpages.com:9000/user/john/abc.txt"); FileSystem fs = FileSystem.get(new Configuration()); BufferedReader br=new BufferedReader(new

Using mongodb map/reduce in php

流过昼夜 提交于 2019-12-25 17:16:37
问题 I'm new to mongodb and I want to use mongo map/reduce function in my php codes connected to my mongo database. I have a document named videos with a large number of items, I want to get 10 items that have the largest values in specific field named "fc_total_share". And by the way, as my "videos" document has really large number of items, do you think that map/reduce is a good way to retrieve specific items and if not would you guys please help me to find a better way. 回答1: You can do this

Ended Job = job_local644049657_0014 with errors Error during job, obtaining debugging information

谁说胖子不能爱 提交于 2019-12-25 16:42:28
问题 How to find the log file Please guide I have checked in the url of Resouce manager. But i didnt find any log file This is the complete error Query ID = hadoop_20170325120040_d54d136a-1904-4af9-8f8d-4167343db072 Total jobs = 1 Launching Job 1 out of 1 Number of reduce tasks is set to 0 since there's no reduce operator Job running in-process (local Hadoop) 2017-03-25 12:00:42,954 Stage-0 map = 0%, reduce = 0% Ended Job = job_local644049657_0014 with errors Error during job, obtaining debugging

Pig gives me this error when I tried dump the data

强颜欢笑 提交于 2019-12-25 16:08:31
问题 I used following 3 statments to read a data which was present in hdfs and then dump the data while using pig in mapreduce mode it gives me following huge error please can somebody expalin it to me or provide solution please grunt> a= load '/temp' AS (name:chararray, age:int, salary:int); grunt> b= foreach a generate (name, salary); grunt> dump b; 2017-04-19 20:47:00,463 [main] INFO org.apache.pig.tools.pigstats.ScriptState - Pig features used in the script: UNKNOWN 2017-04-19 20:47:00,544

mutual friend using MapReduce in MongoDB

两盒软妹~` 提交于 2019-12-25 14:12:39
问题 i am trying MapReduce in MongoDB, i have MongoDB collection with following data type { "_id" : ObjectId("57aea85af405910cfcd2bfeb"), "friendList" : [ "Karma", " Tom", " Ram", " Bindu", " Shiva", " Kishna", " Bikash", " Bakshi", " Dinesh" ], "user" : "Hari" } { "_id" : ObjectId("57aea85bf405910cfcd2bfec"), "friendList" : [ "Karma", " Sita", " Bakshi", " Hanks", " Shyam", " Bikash" ], "user" : "Howard" } { "_id" : ObjectId("57aea85cf405910cfcd2bfed"), "friendList" : [ "Dinesh", " Ram", " Hanks"

mutual friend using MapReduce in MongoDB

对着背影说爱祢 提交于 2019-12-25 14:12:16
问题 i am trying MapReduce in MongoDB, i have MongoDB collection with following data type { "_id" : ObjectId("57aea85af405910cfcd2bfeb"), "friendList" : [ "Karma", " Tom", " Ram", " Bindu", " Shiva", " Kishna", " Bikash", " Bakshi", " Dinesh" ], "user" : "Hari" } { "_id" : ObjectId("57aea85bf405910cfcd2bfec"), "friendList" : [ "Karma", " Sita", " Bakshi", " Hanks", " Shyam", " Bikash" ], "user" : "Howard" } { "_id" : ObjectId("57aea85cf405910cfcd2bfed"), "friendList" : [ "Dinesh", " Ram", " Hanks"