how to write mapreduce program in hadoop

So that any executable program supporting standard I/O (stdin, stdout) can become hadoop er or reducer. For example:Copy codeThe Code is as follows:Hadoop jar hadoop-streaming.jar-input SOME_INPUT_DIR_OR_FILE-output SOME_OUTPUT_DIR-mapper/bin/cat-CER/usr/bin/wc In this example, the cat and wc tools provided by Unix/Linux are used as mapper/reducer. Is it amazing?

Enables any executable program that supports standard IO (stdin, stdout) to be a mapper or reducer of Hadoop. For example: Copy Code code as follows: Hadoop jar Hadoop-streaming.jar-input Some_input_dir_or_file-output Some_output_dir-mapper/bin/cat-reducer/usr/bin /wc In this case, the use of Un

Hadoop does not use HDFS in stand-alone mode, nor does it open any Hadoop daemons, and all programs run on one JVM and allow up to one reducer Create a new Hadoop-test Java project in eclipse (especially if Hadoop requires 1.6 or more versions of JDK 1.6) Download hadoop-1.2

Original: http://xiaoxia.org/2011/12/18/map-reduce-program-of-rmm-word-count-on-hadoop/Running a MapReduce program based on RMM Chinese word segmentation algorithm on Hadoop 23 repliesI know the title of this article is very "academic", very vulgar, people seem to be a very

-generated Method StubString[] arg={"Hdfs://hadoop:9000/user/root/input/cite75_99.txt", "Hdfs://hadoop:9000/user/root/output"};int res = Toolrunner.run (new Configuration (), New MyJob1 (), ARG);System.exit (RES);} public int run (string[] args) throws Exception {TODO auto-generated Method StubConfiguration conf = getconf ();jobconf job = new jobconf (conf, myjob1.class);Path in = new Path (args[0]);Path ou

Create a map/reduce Project in eclipse 1. Create the MyMap. java file. Import java. io. IOException;Import java. util. StringTokenizer;Import org. apache. hadoop. io. IntWritable;Import org. apache. hadoop. io. Text;Import org. apache. hadoop. mapreduce. Mapper;Public class MyMap extends Mapper Private final static Int

Hadoop Streaming is a tool for Hadoop that allows users to write MapReduce programs in other languages, and users can perform map/reduce jobs simply by providing mapper and reducer For information, see the official Hadoop streaming document. 1, the following to achieve word

Summary: The MapReduce program makes a word count. Keywords: MapReduce program word Count Data Source: Manual construction of English document File1.txt,file2.txt. File1.txt content Hello Hadoop I am studying the Hadoop technology

Sharing reason: Although a blog post to write questions feel a bit extravagant, but search Baidu, related articles too little, struggling to find a log to solve the solution.Problem: The MapReduce program developed on the Windows platform has been slow to run.MapReduce Program Public classTest { Public Static voidMain

procedureMake the Java program into a jar package and upload it to the Hadoop server (any Namenode node on the boot)3. Data sourceThe data source is as follows:Hadoop java text hdfstom Jack Java textjob hadoop ABC lusihdfs Tom textPut the content in a TXT file and put it in HDFs/usr/input (under HDFs, not Linux), and you can upload it using the Eclipse plugin:4.

(Deletedataduplicationreducer.class);Job.setoutputkeyclass (Text.class);Job.setoutputvalueclass (Text.class); Fileinputformat.addinputpath (Job,new Path (otherargs[0]));Fileoutputformat.setoutputpath (Job,new Path (otherargs[1]));System.exit (Job.waitforcompletion (true)? 0:1);}} 3 Execution procedures For information on how to execute a program, you can refer to the implementation procedure in the article "Application II of the

exitCode = -1; ProgramDriver pgd = new ProgramDriver(); try { pgd.addClass("singlewordcount", SingleWordCount.class, "A map/reduce program that counts the words in the input files."); pgd.driver(argv); // Success exitCode = 0; } catch(Throwable e){ e.printStackTrace(); } System.exit(exitCode); }} Then re-package the jar with the above class, double-click the JAR file to ope