hadoop mapreduce tutorial

The first to implement MapReduce is to rewrite two functions, one is map and the other is reducemap(key ,value)The map function has two parameters, one is key, one is valueIf your input type is Textinputformat (default), then the input of your map function will be: Key: The offset of the file (that is, the values in the location of the file) Value: This is a line of string (Hadoop takes each line o

Hadoop mapreduce custom grouping RawComparator and hadoopmapreduce This article is published on my blog. Next, I wrote the article "Hadoop mapreduce custom sorting WritableComparable" last time. In order of this, I should explain how to implement the custom grouping. I will not talk about the operation sequence here, f

WRITABLECOMPARABLClasses of e can be compared to each other. All classes that are used as key should implement this interface. * Reporter can be used to report the running progress of the entire application, which is not used in this example. * */public static class Map extends Mapreducebase implements Mapper (1) The process of map-reduce mainly involves the following four parts: client-side: For submitting Map-reduce Task Job Jobtracker: Coordinating the entire job's operation, wh

MapReduce has PHP interface, ask the bottom source who knows where, want to learn There will probably be some interaction between PHP and Java. Reply content: MapReduce has PHP interface, ask the bottom source who knows where, want to learnThere will probably be some interaction between PHP and Java. Using PHP to write a mapreduce program for

Write the MapReduce program to implement the Kmeans algorithm. Our idea may be1. centroid after the second iteration2. Map. Calculates the distance between each centroid and sample, obtains the centroid with the shortest distance from the sample, takes this centroid as the key, the sample as value, the output3. In reduce, the input key is the centroid, value is the other sample, then again compute the cluster center, put the cluster center into a all

PriviledgedActionException as:man (auth:SIMPLE) cause:java.io.IOException: Cannot initialize Cluster. Please check your configuration for mapreduce.framework.name and the correspond server addresses.2014-09-24 12:57:41,567 ERROR [RunService.java:206] - [thread-id:17 thread-name:Thread-6] threadId:17,Excpetion:java.io.IOException: Cannot initialize Cluster. Please check your configuration for mapreduce.framework.name and the correspond server addresses.at org.apache.hadoop.mapreduce.Cluster.initi

. Jobclient:cpu Time Spent (ms) =1530 13/11/20 16:10:16 INFO mapred. Jobclient:total committed heap usage (bytes) =504758272 13/11/20 INFO 16:10:16. Jobclient:combine input records=4 13/11/20 16:10:16 INFO mapred. jobclient:split_raw_bytes=111 13/11/20 16:10:16 INFO mapred. Jobclient:reduce input records=4 13/11/20 16:10:16 INFO mapred. Jobclient:reduce input groups=4 13/11/20 16:10:16 INFO mapred. Jobclient:combine output records=4 13/11/20 16:10:16 INFO mapred. Jobclient:physical memory (bytes

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. Execute JAR Package# fully qualified name

. ManagementThe Fair Scheduler provides support for two mechanisms for execution-time management: By editing the allocation file, you can change the minimum share, limit, weight, pre-occupancy time difference, and queue scheduling policy.The scheduler will reload the file 10-15 seconds after it knows it has changed. The current app, queue, and fair share can be checked through the ResourceManager Web interface, which is http://ResourceManager URL/cluster/scheduler.Each of the following qu

); 5 Sort grouping//6 set in a certain reduce and key value type Job.setreducerclass (Myreduce.class); Job.setoutputkeyclass (Longwritable.class); Job.setoutputvalueclass (longwritable.cLASS); 7 Set Output directory Fileoutputformat.setoutputpath (Job, New Path (Output_dir)); 8 Submit Job Job.waitforcompletion (TRUE); } static void Deleteoutputfile (String path) throws exception{Configuration conf = new configuration (); FileSystem fs = Filesystem.get (new U

Tags: mapred log images reduce str add technology share image 1.7Use Hadoop MapReduce analyzes MongoDB data (Many internet crawlers now store the data in Mongdb, so they study it and write this document) Copyright NOTICE: This article is Yunshuxueyuan original article.If you want to reprint please indicate the source: http://www.cnblogs.com/sxt-zkys/QQ Technology Group: 299142667 First, the

MapReduce program Local Debug/Hadoop operations local file system Empty the configuration file under Conf in the Hadoop home directory. Running the Hadoop command at this point uses the local file system, which allows you to run the MapReduce program locally and manipula

When using MapReduce and HBase, when running the program, it appearsJava.lang.noclassdeffounderror:org/apache/hadoop/hbase/xxx error, due to the lack of hbase supported jar packs in the running environment of Hadoop, you can resolve 1 by following these methods . Turn off the Hadoop process (all) 2. Add in the profile

Architecture of MapReduce: -Distributed Programming architecture -Data-centric, more emphasis on throughput -Divide and conquer (the operation of large-scale data sets, distributed to a master node under the management of the various nodes together to complete, and then consolidate the intermediate results of each node to get the final output) -map to break a task into multiple subtasks -reduce the decomposed multitasking and summarizes the results

precedence is higher than the attribute defined by the file resource To override a property by using the JVM parameter -dproperty=value on the command line Second, configure the development environment CONF option: Easy to switch configuration files Genericoptionsparser,tool and Toolrunner: Genericoptionsparser A class that explains common Hadoop command-line options, which can be set in the configuration object depending on th

description and submission classespublic class Flowsumrunner extends configured implements tool{public int run (string[] arg0) throws Exception {Configuration conf = new configuration ();Job Job = job.getinstance (conf);Job.setjarbyclass (Flowsumrunner.class);Job.setmapperclass (Flowsummapper.class);Job.setreducerclass (Flowsumreducer.class);Job.setmapoutputkeyclass (Text.class);Job.setmapoutputvalueclass (Flowbean.class);Job.setoutputkeyclass (Text.class);Job.setoutputvalueclass (Flowbean.clas

Hadoop beginners often have two questions: 1. If a hadoop block is 64 MB by default, will a row of records be divided into two blocks for text in the form of a record row? 2. when a file is read from the block for splitting, will a row of records be divided into two inputsplits? If two inputsplits are split, an inputsplit contains a row of incomplete data, will the ER er processing this inputsplit produce i

Hadoop mapreduce jar File Upload When submitting a job, we often execute a command similar to the following: Hadoop jar Wordcount.jar test. WordCount, and then wait for the job to complete to see the results. In the job execution process, the client uploads the jar file into HDFs, then initializes the job by JT and issues the specific task to TT, where we mainly

This article mainly describes how to sort keys by Hadoop. 1. Partition Partition distributes map results to multiple Reduce workers. Of course, multiple reducers can reflect the advantages of distributed systems. 2. Ideas Since each partition is ordered internally, as long as the partitions are ordered, all partitions can be ordered. 3. Problems With the idea, how to define the boundaries of partition is a problem. Solution:

Write the WordCount program data as follows:Hello BeijingHello ShanghaiHello ChongqingHello TianjinHello GuangzhouHello Shenzhen...1, Wcmapper:Package com.hadoop.testHadoop;Import java.io.IOException;Import org.apache.hadoop.io.LongWritable;Import Org.apache.hadoop.io.Text;Import Org.apache.hadoop.mapreduce.Mapper;In 4 generics, the first two are the types that specify mapper input data, Keyin is the type of the input key, and Valuein is the type of the input value.The data input and output of m