MapReduce

java.lang.NoClassDefFoundError in Hadoop Basics' MapReduce Program

由 ぃ、小莉子 提交于 2020-01-23 01:33:32
问题 I'm trying Hadoop's Basic MapReduce Program whose tutorial is on http://java.dzone.com/articles/hadoop-basics-creating The Full code of the class is(the code is present on net on above url) import java.io.IOException; import java.util.StringTokenizer; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Mapper; import

Hadoop configuration: mapred.* vs mapreduce.*

由 非 Y 不嫁゛ 提交于 2020-01-22 18:56:06
问题 I noticed that there are two sets of Hadoop configuration parameters: one with mapred.* and the other with mapreduce. . I am guessing these might be due to old API vs. new API but if I am not mistaken, these seem to coexist in the new API. Am I correct? If so, is there a generalized statement what is used for mapred. and what is for mapreduce.*? 回答1: Examining the source for 0.20.2, there are only a few mapreduce.* properties, and they revolve around configuring the job input/output format,

Application failed 2 times due to AM Container: exited with exitCode: 1

由 我与影子孤独终老i 提交于 2020-01-22 17:14:58
问题 I ran a mapreduce job on hadoop-2.7.0 but mapreduce job can't be started and I faced with this bellow error: Job job_1491779488590_0002 failed with state FAILED due to: Application application_1491779488590_0002 failed 2 times due to AM Container for appattempt_1491779488590_0002_000002 exited with exitCode: 1 For more detailed output, check application tracking page:http://erfan:8088/cluster/app/application_1491779488590_0002Then, click on links to logs of each attempt. Diagnostics:

Wrong key class: Text is not IntWritable

由 霸气de小男生 提交于 2020-01-22 09:52:45
问题 This may seem like a stupid question, but I fail to see the problem in my types in my mapreduce code for hadoop As stated in the question the problem is that it is expecting IntWritable but I'm passing it a Text object in the collector.collect of the reducer. My job configuration has the following mapper output classes: conf.setMapOutputKeyClass(IntWritable.class); conf.setMapOutputValueClass(IntWritable.class); And the following reducer output classes: conf.setOutputKeyClass(Text.class);

MapReduce程序--WordCount

由 老子叫甜甜 提交于 2020-01-21 21:51:17
使用eclipse创建一个java程序 1.选择File--New--Project，创建java project 2.导入hadoop的相关jar包 选中项目worldcount右键，选择New--Folder，创建lib文件夹，导入以下文件夹内的jar包 /hadoop/share/hadoop/common/ /hadoop/share/hadoop/common/lib/ /hadoop/share/hadoop/mapreduce/ /hadoop/share/hadoop/hdfs/hadoop-hdfs-2.9.2.jar /hadoop/share/hadoop/yarn/hadoop-yarn-*.jar 3.将jar包添加到工程的构建路径 选中所有jar包，右键Build Path--Add to Build Path 4.在这个例子中实现MapReduce，需要编写三个类 1）WordMapper类：实现Map方法 2）WordReducer类：实现Reduce方法 3）WordMain类：对任务的创建进行部分配置 选中项目worldcount右键，选中New--Class，创建WordMapper类 插入以下代码 package wordcount; import java.io.IOException; import java.util

spark的shuffle机制

由 ▼魔方 西西 提交于 2020-01-21 11:58:11
对于大数据计算框架而言，Shuffle阶段的设计优劣是决定性能好坏的关键因素之一。本文将介绍目前Spark的shuffle实现，并将之与MapReduce进行简单对比。本文的介绍顺序是：shuffle基本概念，MapReduce Shuffle发展史以及Spark Shuffle发展史。 （1） shuffle基本概念与常见实现方式 shuffle，是一个算子，表达的是多对多的依赖关系，在类MapReduce计算框架中，是连接Map阶段和Reduce阶段的纽带，即每个Reduce Task从每个Map Task产生数的据中读取一片数据，极限情况下可能触发M*R个数据拷贝通道（M是Map Task数目，R是Reduce Task数目）。通常shuffle分为两部分：Map阶段的数据准备和Reduce阶段的数据拷贝。首先，Map阶段需根据Reduce阶段的Task数量决定每个Map Task输出的数据分片数目，有多种方式存放这些数据分片： 1） 保存在内存中或者磁盘上（Spark和MapReduce都存放在磁盘上）； 2） 每个分片一个文件（现在Spark采用的方式，若干年前MapReduce采用的方式），或者所有分片放到一个数据文件中，外加一个索引文件记录每个分片在数据文件中的偏移量（现在MapReduce采用的方式）。 在Map端，不同的数据存放方式各有优缺点和适用场景。一般而言

Providing several non-textual files to a single map in Hadoop MapReduce

由 落花浮王杯 提交于 2020-01-21 09:13:08
问题 I'm currently writing distributed application which parses Pdf files with the help of Hadoop MapReduce. Input to MapReduce job is thousands of Pdf files (which mostly range from 100KB to ~2MB), and output is a set of parsed text files. For testing purposes, initially I used WholeFileInputFormat provided in Tom White's Hadoop. The Definitive Guide book, which provides single file to single map. This worked fine with small number of input files, however, it does not work properly with thousands

Error while running Mapreduce(yarn)from windows eclipse

由 南笙酒味 提交于 2020-01-20 07:50:45
问题 I am running a WordCount program from my eclipse. I tried with Hadoop1.x it is running fine. Facing issue while running on hadoop2.x i tried 1)added all xml into my classpath. 2)also tried conf.set(), setting xml properties in conf object. Also in logs it says :-No logs available for container container_1394042163908_0573_01_000001 Application application_1394042163908_0573 failed 2 times due to AM Container for appattempt_1394042163908_0573_000002 exited with exitCode: 1 due to: Exception

Error while running Mapreduce(yarn)from windows eclipse

由 给你一囗甜甜゛ 提交于 2020-01-20 07:50:25
问题 I am running a WordCount program from my eclipse. I tried with Hadoop1.x it is running fine. Facing issue while running on hadoop2.x i tried 1)added all xml into my classpath. 2)also tried conf.set(), setting xml properties in conf object. Also in logs it says :-No logs available for container container_1394042163908_0573_01_000001 Application application_1394042163908_0573 failed 2 times due to AM Container for appattempt_1394042163908_0573_000002 exited with exitCode: 1 due to: Exception

Error while running Mapreduce(yarn)from windows eclipse

由 微笑、不失礼 提交于 2020-01-20 07:49:13
问题 I am running a WordCount program from my eclipse. I tried with Hadoop1.x it is running fine. Facing issue while running on hadoop2.x i tried 1)added all xml into my classpath. 2)also tried conf.set(), setting xml properties in conf object. Also in logs it says :-No logs available for container container_1394042163908_0573_01_000001 Application application_1394042163908_0573 failed 2 times due to AM Container for appattempt_1394042163908_0573_000002 exited with exitCode: 1 due to: Exception
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