how to write mapreduce program in hadoop

Follow the Documentation: http://www.micmiu.com/bigdata/hadoop/hadoop2x-eclipse-mapreduce-demo/installation Configure Eclipse, run WordCount program error: Log4j:warn No appenders could be found forLogger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory). Log4j:warn Please initialize the log4j system Properly.log4j:WARN See http://logging.apache.org/log4j/1.

unchangedPackage the project jar file, put it in the project root directory, run the problem againSourcePackage com.mapreduce;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.lib.input.FileInputFormat;Import Org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;public class Mapreducemain {public static void Main (string[

Method) at Java.net.URLClassLoader.findClass (URL Classloader.java:190) at Java.lang.ClassLoader.loadClass (Classloader.java:60S) at Sun.misc.launcher$appclassloader.loadclass (Launcher.java:301) at Java.lang.ClassLoader.loadClass (Classloader.java:247At JAVA.LANG.CLASS.FORNAME0 (Native Method) at Java.lang.Class.forName (Class.java:247) at Org.apache.hadoop.conf.Configuration.getClassByName (Configuration.java:819) at Org.apache.hadoop.conf.Configuration.getClass (Configuration.java:864)

1. Copy the Mapred-site.xml file to the project 2. Add a local mapred-site.xml configuration to the project, read the configuration file from the local project, and debug in reduce Job Job = new Job (conf, "word count");Conf.addresource ("Classpath:/hadoop01/mapred-site.xml");Conf.set ("Fs.defaultfs", "hdfs://192.168.1.10:9008");Conf.set ("Mapreduce.framework.name", "yarn");Conf.set ("Yarn.resourcemanager.address", "192.168.1.10:8032");Conf.set ("Mapred.remote.os", "Linux"); Conf.set ("Hadoop.j

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

Although we can run some encapsulated instance programs very quickly through shell commands on the Virtual Machine Client, in the application, we still need to write code and deploy it to the server. below, I will talk about the deployment process of a program through the program. After hadoop is started, the

tasks assigned by Jobtracker, managing individual tasksThe performance on each node.Job, a user's every compute request, called a job.Task, each job, need to split up, to multiple servers to complete, split out the execution unit, called the task.Task is divided into Maptask and reducetask two, respectively map operation and reduce operation, according to the job set map class and reduce classIv. WordCount Treatment Process1, the file is split into splits, because the test file is small, so eac

Distributed programming is relatively complex, and Hadoop itself is shrouded in big data, cloud computing and other veils, so many beginners are deterred. In fact, Hadoop is a very easy-to-use distributed programming framework that has been well packaged to mask the complexities of many distributed environments, making it easy and easy to divert for ordinary developers.Most

Writing a simple mapreduce program requires the following three steps: 1) Implement Mapper, process input pairs, and output intermediate results; 2) Implement CER, calculate intermediate results, and output the final results; 3) define the running job in the main method, define a job, and control how the job runs here. This article uses an example (Word Count statistics) to demonstrate basic

1, through the traditional Key-value class analysis dataWhen you create a key class, all keys inherit the Writablecomparable interfacepublic class Sendorkey implements Writablecomparable{Default Constructor+parameterized constructorImplementation of ReadFields methodImplementation of Write methodOverriding the Compare to method}Sensorkey.javaSensorvalue.java"Note: The default constructor initializes the variableConstructors with parameters initialize

stage, map output is transmitted to the reduce task, including sorting and grouping of key-value pairs.1. Map stage The map task is very simple. We only need to extract the year and the corresponding temperature value from the input file, and filter out bad records. Here, we select the text input format (default). Each row of the dataset serves as the value in key-value pair in the map task input, the key value is the shift of the corresponding row in the input file (in bytes), but we do not ne

Premise: You have built a Hadoop 2.x Linux environment and are able to run successfully. There is also a window that can access the cluster. Over1.Hfds-site.xml Add attribute: Turn off the permissions check of the cluster, Windows users are generally not the same as the Linux, directly shut it down OK. Remember, it's not core-site.xml rebooting the cluster.2.Hadoop-eclipse-plugin-2.7.0.jar put the plugin in

Premise: You have built a Linux environment for Hadoop 2.x and can execute it successfully. There is also a window to access the cluster. Over1.Hfds-site.xml Add attribute: Turn off permissions validation for the cluster. Windows users are generally not the same as Linux, just shut it down. Remember, not core-site.xml reboot the cluster2.Hadoop-eclipse-plugin-2.7.0.jar put the plugin under the Plugins folde

Rhadoop is an open source project initiated by Revolution Analytics, which combines statistical language R with Hadoop. Currently, the project consists of three R packages, the RMR that support the use of R to write MapReduce applications , Rhdfs for the R language to access HDFs, and for R language Access The rhbase of HBase . Download URL for https://github.c

Fileoutputformat.setoutputpath (Job, New Path (Out_path)); Submit the job to Jobtracker run Job.waitforcompletion (true); } } 1. Select the program entry to be packaged in the Eclipse project and click the right button to select Export 2. Click the jar file option in the Java folder 3. Select the Java file to be beaten into a jar package and the output directory of the jar package 4. Click Next 5. Select the entry of the

and Sqoopwriting a program to put data into HDFs is better than using existing tools. Because there are now very mature tools to do this, and have covered most of the demand. Flume is a tool for Apache's massive data movement. One of the typical applications isdeploy the flume on a Web server machine,collect the logs on the Web server and import them into HDFs. It also supports various log writes. Sqoop is also an Apache tool used to bulk import larg

Mapreduce debugging on a single machine recently Program At that time, because Code With Chinese characters in it, I changed the eclipse encoding from default to utf8 to GBK, and then found that the code can run to the program and cannot run now. Java. Io. ioexception: expecting a line not the end of streamAt org. Apache.