2009-05-19 04:20:40 +00:00
|
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
|
|
|
|
<html>
|
|
|
|
|
<!--
|
|
|
|
|
Licensed to the Apache Software Foundation (ASF) under one or more
|
|
|
|
|
contributor license agreements. See the NOTICE file distributed with
|
|
|
|
|
this work for additional information regarding copyright ownership.
|
|
|
|
|
The ASF licenses this file to You under the Apache License, Version 2.0
|
|
|
|
|
(the "License"); you may not use this file except in compliance with
|
|
|
|
|
the License. You may obtain a copy of the License at
|
|
|
|
|
|
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
|
|
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
|
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
|
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
|
|
|
See the License for the specific language governing permissions and
|
|
|
|
|
limitations under the License.
|
|
|
|
|
-->
|
|
|
|
|
<head>
|
|
|
|
|
<title>Hadoop</title>
|
|
|
|
|
</head>
|
|
|
|
|
<body>
|
|
|
|
|
|
|
|
|
|
Hadoop is a distributed computing platform.
|
|
|
|
|
|
|
|
|
|
<p>Hadoop primarily consists of the <a
|
2011-06-12 22:00:51 +00:00
|
|
|
href="org/apache/hadoop/hdfs/package-summary.html">Hadoop Distributed FileSystem
|
2009-05-19 04:20:40 +00:00
|
|
|
(HDFS)</a> and an
|
2011-06-12 22:00:51 +00:00
|
|
|
implementation of the <a href="org/apache/hadoop/mapred/package-summary.html">
|
2009-05-19 04:20:40 +00:00
|
|
|
Map-Reduce</a> programming paradigm.</p>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<p>Hadoop is a software framework that lets one easily write and run applications
|
|
|
|
|
that process vast amounts of data. Here's what makes Hadoop especially useful:</p>
|
|
|
|
|
<ul>
|
|
|
|
|
<li>
|
|
|
|
|
<b>Scalable</b>: Hadoop can reliably store and process petabytes.
|
|
|
|
|
</li>
|
|
|
|
|
<li>
|
|
|
|
|
<b>Economical</b>: It distributes the data and processing across clusters
|
|
|
|
|
of commonly available computers. These clusters can number into the thousands
|
|
|
|
|
of nodes.
|
|
|
|
|
</li>
|
|
|
|
|
<li>
|
|
|
|
|
<b>Efficient</b>: By distributing the data, Hadoop can process it in parallel
|
|
|
|
|
on the nodes where the data is located. This makes it extremely rapid.
|
|
|
|
|
</li>
|
|
|
|
|
<li>
|
|
|
|
|
<b>Reliable</b>: Hadoop automatically maintains multiple copies of data and
|
|
|
|
|
automatically redeploys computing tasks based on failures.
|
|
|
|
|
</li>
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<h2>Requirements</h2>
|
|
|
|
|
|
|
|
|
|
<h3>Platforms</h3>
|
|
|
|
|
|
|
|
|
|
<ul>
|
|
|
|
|
<li>
|
|
|
|
|
Hadoop was been demonstrated on GNU/Linux clusters with 2000 nodes.
|
|
|
|
|
</li>
|
|
|
|
|
<li>
|
|
|
|
|
Win32 is supported as a <i>development</i> platform. Distributed operation
|
|
|
|
|
has not been well tested on Win32, so this is not a <i>production</i>
|
|
|
|
|
platform.
|
|
|
|
|
</li>
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<h3>Requisite Software</h3>
|
|
|
|
|
|
|
|
|
|
<ol>
|
|
|
|
|
<li>
|
|
|
|
|
Java 1.6.x, preferably from
|
|
|
|
|
<a href="http://java.sun.com/javase/downloads/">Sun</a>.
|
|
|
|
|
Set <tt>JAVA_HOME</tt> to the root of your Java installation.
|
|
|
|
|
</li>
|
|
|
|
|
<li>
|
|
|
|
|
ssh must be installed and sshd must be running to use Hadoop's
|
|
|
|
|
scripts to manage remote Hadoop daemons.
|
|
|
|
|
</li>
|
|
|
|
|
<li>
|
|
|
|
|
rsync may be installed to use Hadoop's scripts to manage remote
|
|
|
|
|
Hadoop installations.
|
|
|
|
|
</li>
|
|
|
|
|
</ol>
|
|
|
|
|
|
|
|
|
|
<h4>Additional requirements for Windows</h4>
|
|
|
|
|
|
|
|
|
|
<ol>
|
|
|
|
|
<li>
|
|
|
|
|
<a href="http://www.cygwin.com/">Cygwin</a> - Required for shell support in
|
|
|
|
|
addition to the required software above.
|
|
|
|
|
</li>
|
|
|
|
|
</ol>
|
|
|
|
|
|
|
|
|
|
<h3>Installing Required Software</h3>
|
|
|
|
|
|
|
|
|
|
<p>If your platform does not have the required software listed above, you
|
|
|
|
|
will have to install it.</p>
|
|
|
|
|
|
|
|
|
|
<p>For example on Ubuntu Linux:</p>
|
|
|
|
|
<p><blockquote><pre>
|
|
|
|
|
$ sudo apt-get install ssh<br>
|
|
|
|
|
$ sudo apt-get install rsync<br>
|
|
|
|
|
</pre></blockquote></p>
|
|
|
|
|
|
|
|
|
|
<p>On Windows, if you did not install the required software when you
|
|
|
|
|
installed cygwin, start the cygwin installer and select the packages:</p>
|
|
|
|
|
<ul>
|
|
|
|
|
<li>openssh - the "Net" category</li>
|
|
|
|
|
<li>rsync - the "Net" category</li>
|
|
|
|
|
</ul>
|
|
|
|
|
|
|
|
|
|
<h2>Getting Started</h2>
|
|
|
|
|
|
|
|
|
|
<p>First, you need to get a copy of the Hadoop code.</p>
|
|
|
|
|
|
|
|
|
|
<p>Edit the file <tt>conf/hadoop-env.sh</tt> to define at least
|
|
|
|
|
<tt>JAVA_HOME</tt>.</p>
|
|
|
|
|
|
|
|
|
|
<p>Try the following command:</p>
|
|
|
|
|
<tt>bin/hadoop</tt>
|
|
|
|
|
<p>This will display the documentation for the Hadoop command script.</p>
|
|
|
|
|
|
|
|
|
|
<h2>Standalone operation</h2>
|
|
|
|
|
|
|
|
|
|
<p>By default, Hadoop is configured to run things in a non-distributed
|
|
|
|
|
mode, as a single Java process. This is useful for debugging, and can
|
|
|
|
|
be demonstrated as follows:</p>
|
|
|
|
|
<tt>
|
|
|
|
|
mkdir input<br>
|
|
|
|
|
cp conf/*.xml input<br>
|
|
|
|
|
bin/hadoop jar hadoop-*-examples.jar grep input output 'dfs[a-z.]+'<br>
|
|
|
|
|
cat output/*
|
|
|
|
|
</tt>
|
|
|
|
|
<p>This will display counts for each match of the <a
|
|
|
|
|
href="http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.html">
|
|
|
|
|
regular expression.</a></p>
|
|
|
|
|
|
|
|
|
|
<p>Note that input is specified as a <em>directory</em> containing input
|
|
|
|
|
files and that output is also specified as a directory where parts are
|
|
|
|
|
written.</p>
|
|
|
|
|
|
|
|
|
|
<h2>Distributed operation</h2>
|
|
|
|
|
|
|
|
|
|
To configure Hadoop for distributed operation you must specify the
|
|
|
|
|
following:
|
|
|
|
|
|
|
|
|
|
<ol>
|
|
|
|
|
|
|
|
|
|
<li>The NameNode (Distributed Filesystem master) host. This is
|
|
|
|
|
specified with the configuration property <tt><a
|
|
|
|
|
href="../core-default.html#fs.default.name">fs.default.name</a></tt>.
|
|
|
|
|
</li>
|
|
|
|
|
|
2011-06-12 22:00:51 +00:00
|
|
|
<li>The {@link org.apache.hadoop.mapred.JobTracker} (MapReduce master)
|
2009-05-19 04:20:40 +00:00
|
|
|
host and port. This is specified with the configuration property
|
|
|
|
|
<tt><a
|
2011-06-12 22:00:51 +00:00
|
|
|
href="../mapred-default.html#mapreduce.jobtracker.address">mapreduce.jobtracker.address</a></tt>.
|
2009-05-19 04:20:40 +00:00
|
|
|
</li>
|
|
|
|
|
|
|
|
|
|
<li>A <em>slaves</em> file that lists the names of all the hosts in
|
|
|
|
|
the cluster. The default slaves file is <tt>conf/slaves</tt>.
|
|
|
|
|
|
|
|
|
|
</ol>
|
|
|
|
|
|
|
|
|
|
<h3>Pseudo-distributed configuration</h3>
|
|
|
|
|
|
|
|
|
|
You can in fact run everything on a single host. To run things this
|
|
|
|
|
way, put the following in:
|
|
|
|
|
<br/>
|
|
|
|
|
<br/>
|
|
|
|
|
conf/core-site.xml:
|
|
|
|
|
<xmp><configuration>
|
|
|
|
|
|
|
|
|
|
<property>
|
|
|
|
|
<name>fs.default.name</name>
|
|
|
|
|
<value>hdfs://localhost/</value>
|
|
|
|
|
</property>
|
|
|
|
|
|
|
|
|
|
</configuration></xmp>
|
|
|
|
|
|
|
|
|
|
conf/hdfs-site.xml:
|
|
|
|
|
<xmp><configuration>
|
|
|
|
|
|
|
|
|
|
<property>
|
|
|
|
|
<name>dfs.replication</name>
|
|
|
|
|
<value>1</value>
|
|
|
|
|
</property>
|
|
|
|
|
|
|
|
|
|
</configuration></xmp>
|
|
|
|
|
|
|
|
|
|
conf/mapred-site.xml:
|
|
|
|
|
<xmp><configuration>
|
|
|
|
|
|
|
|
|
|
<property>
|
2011-06-12 22:00:51 +00:00
|
|
|
<name>mapreduce.jobtracker.address</name>
|
2009-05-19 04:20:40 +00:00
|
|
|
<value>localhost:9001</value>
|
|
|
|
|
</property>
|
|
|
|
|
|
|
|
|
|
</configuration></xmp>
|
|
|
|
|
|
|
|
|
|
<p>(We also set the HDFS replication level to 1 in order to
|
|
|
|
|
reduce warnings when running on a single node.)</p>
|
|
|
|
|
|
|
|
|
|
<p>Now check that the command <br><tt>ssh localhost</tt><br> does not
|
|
|
|
|
require a password. If it does, execute the following commands:</p>
|
|
|
|
|
|
|
|
|
|
<p><tt>ssh-keygen -t dsa -P '' -f ~/.ssh/id_dsa<br>
|
|
|
|
|
cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys
|
|
|
|
|
</tt></p>
|
|
|
|
|
|
|
|
|
|
<h3>Bootstrapping</h3>
|
|
|
|
|
|
|
|
|
|
<p>A new distributed filesystem must be formatted with the following
|
|
|
|
|
command, run on the master node:</p>
|
|
|
|
|
|
|
|
|
|
<p><tt>bin/hadoop namenode -format</tt></p>
|
|
|
|
|
|
|
|
|
|
<p>The Hadoop daemons are started with the following command:</p>
|
|
|
|
|
|
|
|
|
|
<p><tt>bin/start-all.sh</tt></p>
|
|
|
|
|
|
|
|
|
|
<p>Daemon log output is written to the <tt>logs/</tt> directory.</p>
|
|
|
|
|
|
|
|
|
|
<p>Input files are copied into the distributed filesystem as follows:</p>
|
|
|
|
|
|
|
|
|
|
<p><tt>bin/hadoop fs -put input input</tt></p>
|
|
|
|
|
|
|
|
|
|
<h3>Distributed execution</h3>
|
|
|
|
|
|
|
|
|
|
<p>Things are run as before, but output must be copied locally to
|
|
|
|
|
examine it:</p>
|
|
|
|
|
|
|
|
|
|
<tt>
|
|
|
|
|
bin/hadoop jar hadoop-*-examples.jar grep input output 'dfs[a-z.]+'<br>
|
|
|
|
|
bin/hadoop fs -get output output
|
|
|
|
|
cat output/*
|
|
|
|
|
</tt>
|
|
|
|
|
|
|
|
|
|
<p>When you're done, stop the daemons with:</p>
|
|
|
|
|
|
|
|
|
|
<p><tt>bin/stop-all.sh</tt></p>
|
|
|
|
|
|
|
|
|
|
<h3>Fully-distributed operation</h3>
|
|
|
|
|
|
|
|
|
|
<p>Fully distributed operation is just like the pseudo-distributed operation
|
|
|
|
|
described above, except, specify:</p>
|
|
|
|
|
|
|
|
|
|
<ol>
|
|
|
|
|
|
|
|
|
|
<li>The hostname or IP address of your master server in the value
|
|
|
|
|
for <tt><a
|
|
|
|
|
href="../core-default.html#fs.default.name">fs.default.name</a></tt>,
|
|
|
|
|
as <tt><em>hdfs://master.example.com/</em></tt> in <tt>conf/core-site.xml</tt>.</li>
|
|
|
|
|
|
|
|
|
|
<li>The host and port of the your master server in the value
|
2011-06-12 22:00:51 +00:00
|
|
|
of <tt><a href="../mapred-default.html#mapreduce.jobtracker.address">mapreduce.jobtracker.address</a></tt>
|
2009-05-19 04:20:40 +00:00
|
|
|
as <tt><em>master.example.com</em>:<em>port</em></tt> in <tt>conf/mapred-site.xml</tt>.</li>
|
|
|
|
|
|
|
|
|
|
<li>Directories for <tt><a
|
|
|
|
|
href="../hdfs-default.html#dfs.name.dir">dfs.name.dir</a></tt> and
|
|
|
|
|
<tt><a href="../hdfs-default.html#dfs.data.dir">dfs.data.dir</a>
|
|
|
|
|
in <tt>conf/hdfs-site.xml</tt>.
|
|
|
|
|
</tt>These are local directories used to hold distributed filesystem
|
|
|
|
|
data on the master node and slave nodes respectively. Note
|
|
|
|
|
that <tt>dfs.data.dir</tt> may contain a space- or comma-separated
|
|
|
|
|
list of directory names, so that data may be stored on multiple local
|
|
|
|
|
devices.</li>
|
|
|
|
|
|
2011-06-12 22:00:51 +00:00
|
|
|
<li><tt><a href="../mapred-default.html#mapreduce.cluster.local.dir">mapreduce.cluster.local.dir</a></tt>
|
2009-05-19 04:20:40 +00:00
|
|
|
in <tt>conf/mapred-site.xml</tt>, the local directory where temporary
|
|
|
|
|
MapReduce data is stored. It also may be a list of directories.</li>
|
|
|
|
|
|
|
|
|
|
<li><tt><a
|
2011-06-12 22:00:51 +00:00
|
|
|
href="../mapred-default.html#mapreduce.job.maps">mapreduce.job.maps</a></tt>
|
2009-05-19 04:20:40 +00:00
|
|
|
and <tt><a
|
2011-06-12 22:00:51 +00:00
|
|
|
href="../mapred-default.html#mapreduce.job.reduces">mapreduce.job.reduces</a></tt>
|
2009-05-19 04:20:40 +00:00
|
|
|
in <tt>conf/mapred-site.xml</tt>.
|
|
|
|
|
As a rule of thumb, use 10x the
|
2011-06-12 22:00:51 +00:00
|
|
|
number of slave processors for <tt>mapreduce.job.maps</tt>, and 2x the
|
|
|
|
|
number of slave processors for <tt>mapreduce.job.reduces</tt>.</li>
|
2009-05-19 04:20:40 +00:00
|
|
|
|
|
|
|
|
</ol>
|
|
|
|
|
|
|
|
|
|
<p>Finally, list all slave hostnames or IP addresses in your
|
|
|
|
|
<tt>conf/slaves</tt> file, one per line. Then format your filesystem
|
|
|
|
|
and start your cluster on your master node, as above.
|
|
|
|
|
|
|
|
|
|
</body>
|
|
|
|
|
</html>
|
|
|
|
|
|
