Error 1. [[emailprotected] hadoop]# ant-dversion=1.2.1 Examples Error: The main class could not be found or could not be loaded Org.apache.tools.ant.launch.Launcher Solution Export classpath=.:${java_home}/lib:${jre_home}/lib:/usr/share/ant/lib/ Ant-launcher.jar Error 2:build Failed/usr/local/hadoop/build.xml:634:execute failed:java.io.IOException:Cannot run Program ' autoreconf ' (in Directory "/usr/local/
-io-${commons-io.version}.jar,
lib/htrace-core- ${htrace.version}-incubating.jar "/>
Save exit. Note If you do not modify this, even if you compile the jar package and put it in Eclipse, the configuration link will complain.
But just adding and modifying these lib is not going to work, and the jar versions under shar
The first 2 blog test of Hadoop code when the use of this jar, then it is necessary to analyze the source code.
It is necessary to write a wordcount before analyzing the source code as follows
Package mytest;
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
Previously introduced me in Ubuntu under the combination of virtual machine Centos6.4 build hadoop2.7.2 cluster, in order to do mapreduce development, to use eclipse, and need the corresponding Hadoop plug-in Hadoop-eclipse-plugin-2.7.2.jar, first of all, before the hadoop1.x in the official Hadoop installation package
I. Hadoop-eclipse-plugin-2.7.3.jar plugin download Click to download the plugin into the installation directory of Eclipse DropinsThird, the configuration on eclipse3.1 Opening Window-->persperctive-->other3.2 Select Map\/reduce, click OK3.3 Click the image icon to add a cluster3.4 The
How to compile your own build eclipse plugin, such as Hadoop-eclipse-plugin-2.2.0.jarhttp://cxshun.iteye.com/blog/1876366Big data is a hot topic today, I believe that the Java of course we can not miss, especially in the big data era of Hadoop beloved is our Java community (the core is written in Java).See Hadoop, be
Sometimes we need to check the source code of the referenced jar package, which can be achieved through simple configuration.
Prerequisites: Download the source code of the jar package to your computer.
Example: to view the source code of the struts2-core-2.2.1.1.jar a
Today, HDFS, the core of hadoop, is very important. It is a distributed file system. Why does hadoop support massive data storage? In fact, it depends mainly on the HDFS capability, mainly on the ability of HDFS to store massive data.
1. Why can HDFS store massive data?
In the beginning, let's think about this problem. I don't need to talk about the basic concept
hadoop-1.2.1 Pseudo-distributed set up, but also just run through the Hadoop-example.jar package wordcount, all this looks so easy.But unexpectedly, his own Mr Program, run up to encounter the no job file jar and classnotfoundexception problems.After a few twists and ends, the MapReduce I wrote was finally successfully run.I did not add a third-party
hadoop modules.
Hadoop Distributed File System (HDFS™): A distributed file system that provides high-throughput access to application data.
Hadoop yarn: A Framework for Job Scheduling and cluster resource management.
Hadoop mapreduce: a yarn-based system for parallel processing of large data sets. www.169it.com
Lates
mahout (or Hadoop) takes precedence over loading jar packages with user-specified classpathProblem: When using mahout0.8, Java.lang.NoSuchMethodError:org.apache.lucene.util.PriorityQueue appearsSimilar http://www.warski.org/blog/2013/10/using-amazons-elastic-map-reduce-to-compute-recommendations-with-apache-mahout-0-8/Reason:$HADOOP _home/lib There is an old vers
Let 's talk about spring many jar package features, whether for beginners spring novice, or Spring master, this article will bring you the knowledge of the harvest, if you are already very familiar with the content of this article as a restudying bar. Spring.jar is a single jar package that contains a full release. Spring.jar In addition to the content contained in the Spring-mock.jar, all the contents of
decompression succeeded, the reason why the file is not found is the directory problem, this will be studied in detail under the 3 packaging method, no longer repeat. :Summary:-archives is a very useful parameter, but in particular, you should pay attention to the directory problem in use.Reference:Http://blog.javachen.com/2015/02/12/hadoop-streaming.htmlHttp://hadoop.apache.org/docs/r2.6.0/hadoop-mapreduc
-dcom.sun.management.jmxremote.port=1499 $HADOOP _client_opts " This will open a port on the machine executing the Hadoop jar, which is determined by the -dcom.sun.management.jmxremote.port=1499 parameter.2. Start a mapreduce program, bash-4.1$ Hadoop jar /home/yanliming/
Requirements for JDK versions
Hadoop 2.7 and later versions require JDK 7;
Hadoop 2.6 and previous versions support JDK 6;
for the hadoop1.x.x version, you only need to introduce 1 jars:Hadoop-core
for the hadoop2.x.x version, you need to introduce 4 jars:Hadoop-common
Hadoop-hdfs
, and is pre-sorted for efficiency considerations.Each map task has a ring memory buffer that stores the output of the task. By default,Buffer size is 100MB, once the buffered content reaches the threshold (default is 80%), a background threadThe content is then written to a new overflow file in the disk-specified directory. In the process of writing to disk,The map output continues to be written to the buffer, but if the buffer is filled during this time, the map will block,Until the write disk
for analysis and processing(5)/app-non-data files, such as: Configuration files, jar files, SQL files, etc. Mastering the above four steps for the application of HDFs has important role and significance, but we should be based on their own situation gradually, pay attention to practice, can continue to make progress. I usually like to find some case analysis, so as to exercise to improve their skills, this is more like "Big Data CN" This service plat
Uploading and downloading files on HDFs is the basic operation of the cluster, in the guide to Hadoop, there are examples of code for uploading and downloading files, but there is no clear way to configure the Hadoop client, after lengthy searches and debugging, How to configure a method for using clustering, and to test the available programs that you can use to manipulate files on the cluster. First, you
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