advantages of using hadoop

value inside the map functionAppendix:How to work with multiple files, one map per file?For example, to compress (zipping) some files on a cluster, you can use the following methods: Using Hadoop streaming and user-written mapper scripts: Generate a file containing the full path of all files to be compressed on HDFs. Each map task obtains a path name as input. Create a mapper scri

Introduction The Hadoop mapreduce job has a unique code architecture that has a specific template and structure. Such a framework can cause some problems with test-driven development and unit testing. This article is a real example of the use of Mrunit,mockito and Powermock. I'll introduce Using Mrunit to write JUnit tests for Hadoop mapreduce applications

Pom.xmlDependency> groupId>Org.apache.hadoopgroupId> Artifactid>Hadoop-commonArtifactid> version>2.5.1version> Dependency> Dependency> groupId>Org.apache.hadoopgroupId> Artifactid>Hadoop-hdfsArtifactid> version>2.5.1version> Dependency> Dependency> groupId>Org.apache.hadoopgroupId> Artifactid>Hadoop-clientArtifactid>

The example Terasort in Hadoop is an example of sorting using Mapredue. This article references and simplifies this example: The basic idea of sequencing is to take advantage of the automatic sequencing of MapReduce, in Hadoop, from the map to the reduce phase, the map structure will be assigned to each key according to the hash value of each reduce, wherein in r

When using virtual machine to build hadoop cluster core-site.xml file error, how to solve ?,When using virtual machine to build hadoop cluster core-site.xml file error, how to solve? Problem: errors in core-site.xml files The value here cannot be in the/tmp folder. Otherwise, datanode cannot be started when the inst

This article describes the configuration method for using the HDFs Java API.1, first solve the dependence, pomDependency> groupId>Org.apache.hadoopgroupId> Artifactid>Hadoop-clientArtifactid> version>2.7.2version> Scope>ProvidedScope> Dependency>2, configuration files, storage HDFs cluster configuration information, basically from Core-site.xml and Hdfs-sit

row format delimited fields terminated by ' \ t ' as select $CURRENT , Ip,count (*) as hits from Bbslog where logdate= $CURRENT GROUP by IP have hits > order by hits DESC "#查询uv/home/cloud/hive/bin/hive-e "CREATE table uv_$current row format delimited fields terminated by ' \ t ' as SELECT COUNT (Dist Inct IP) from Bbslog where logdate= $CURRENT "#查询每天的注册人数/home/cloud/hive/bin/hive-e "CREATE table reg_$current row format delimited fields terminated by ' \ t ' as SELECT COUNT (*) From Bbslog whe

1, first in eclipse-"help-" Eclipse Marketplace search maven plugin download.Note that the plugin will correspond to the eclipse version, my eclipse version is Luna, the plugin will download the Luna version, I downloaded Maven integration for Eclipse (Luna and newer) 1.5. Otherwise, the new MAVEN project did not bring Java engineering.2, other environment configuration and Hadoop configuration see the reference link.3, I use is hadoop2.4.0. The pom f

Tags: Java I/O problems, ad on C Learning ProgramIn the virtual machine, rhel6.5 is used to install a standalone pseudo-distributed hadoop, and Java API is used to develop programs on the host machine. Some problems have been encountered and solved: 1. Disable iptables when the connection fails, the simplest and most crude way to set a policy is to allow remote access to the port. Note: You must call it under root. #> service iptables stop2. The error

virtual machine NAME02 on the right-click Pop-up menu, tap " Management (M) " , then click on the Right drop-down menu " Cloning (C) " , as shown below:13.2, continue to the next step13.3, select Create Complete clone (F)13.4, set the name and so on, click Finish13.5, start copying, time is longer, wait patiently, as followsClick the Close button to complete this Clone . In using the same method, clone another data02 out as shown:OK, the last 3 iden

Reprint Please specify source: http://blog.csdn.net/xiaojimanman/article/details/40372189The WordCount case in the Hadoop source code implements the word statistics, but the output to the HDFs file, the online program wants to use its calculation results and also to write a program again, so I study about the MapReduce output problem, Here's a simple example of how to output the results of a mapreduce calculation to a database.Requirements Description

(Text.class); Job.setmapoutputvalueclass (Longwritable.class); Job.setreducerclass (Jreducer.class); Job.setoutputkeyclass (Text.class); Job.setoutputvalueclass ( Longwritable.class); Fileoutputformat.setoutputpath (Job, Outpath); Job.setoutputformat (textoutputformat.class);// Use Jobclient.runjob instead of job.waitForCompletionJobClient.runJob (job);}}Can seeIn fact, the old version of the API is not very different, just a few classes replaced itNote that the old version of the API class is

database you are using (Note: If database does not exist, a will be created, and MongoDB will delete the database if it exits without any action) Db.auth (Username,password) Username for username, password for password login to the database you want to use Db.getcollectionnames () See what tables are in the current database Db. [Collectionname].insert ({...}) Add a document record to the specified database Db. [Collectionname].findone () finds the

CD hadoop-2.4.1/lib/nativeFile libhadoop.so.1.0.0 to view your own version of HadoopView dependent libraries with the LDD commandLDD libhadoop.so.1.0.0LDD--version native version of GCChttp://blog.csdn.net/l1028386804/article/details/51538611Should be due to the GCC version of the problem, this will be compiled for a long time, so the solution is to comment out the log4j inside, or in the beginning of the installation of Linux after the upgrade and gl

The procedure is as follows: PackageCom.lcy.hadoop.examples;Importorg.apache.hadoop.conf.Configuration;Importorg.apache.hadoop.io.IOUtils;ImportOrg.apache.hadoop.io.compress.CompressionCodec;ImportOrg.apache.hadoop.io.compress.CompressionOutputStream;Importorg.apache.hadoop.util.ReflectionUtils; Public classStreamcompressor { Public Static voidMain (string[] args)throwsexception{//TODO auto-generated Method StubString codecclassname=args[0]; ClassClass.forName (codecclassname); Configuration con

Parameters required for configuration:Configuration conf = new Configuration();conf.set("fs.defaultFS", "hdfs://hadoop2cluster");conf.set("dfs.nameservices", "hadoop2cluster");conf.set("dfs.ha.namenodes.hadoop2cluster", "nn1,nn2");conf.set("dfs.namenode.rpc-address.hadoop2cluster.nn1", "10.0.1.165:8020");conf.set("dfs.namenode.rpc-address.hadoop2cluster.nn2", "10.0.1.166:8020");conf.set("dfs.client.failover.proxy.provider.hadoop2cluster", "org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFai

Today when using bytewritable encountered a problem, wasted a lot of time, and finally by looking at Bytewritable source code to solve this problem. Share it and hope to help others save some time. Himself wrote a class inheriting the recordreader for (byte b:contents) {System.out.print (b);} System.out.println ("Len" + contents.length); Value.set (contents, 0, contents.length); The output is as follows: -27-128-110-26-114-11032-25-76-94-27-68-10732

UFW Default Deny Copy CodeLinux restart:root user restart can use the following command, but ordinary users do not. Init 6 Copy CodeOrdinary users use the following command sudo reboot Copy CodeFive Tests whether the host and the virtual machine are ping through1. Set up the IP, it is recommended that you use the Linux interface, which is more convenient to set up. However, it is best to set the interfaces under/etc/network/through the terminal. Becaus

configuration steps for developing HBase programs using Eclipse1. Create a new generic Java project. 2. --javabuildpath--libraries--addexternaljars, add hadoop installation directory hbase-0.90.5.jar hbase-0.90.5-tests.jar, hbase installation directory lib All in the directory jar file. 3. Create a new conf directory under the project root directory and copy the conf directory under the

Previous Article The method we introduced in "using Hadoop to multiply large Matrices" has the defect of "large storage space occupied by files during computing, this article focuses on solving this problem.Concept of Matrix Multiplication The traditional method of matrix multiplication is to multiply rows and columns, that is, multiply a row of the Left matrix by a column of the right matrix. However, this