Databases Reference
In-Depth Information
With empty configuration files, Hadoop will run completely on the local machine.
Because there's no need to communicate with other nodes, the standalone mode
doesn't use HDFS, nor will it launch any of the Hadoop daemons. Its primary
use is for developing and debugging the application logic of a MapReduce pro-
gram without the additional complexity of interacting with the daemons. When
you ran the example MapReduce program in
chapter 1
, you were running it in
standalone mode.
2.3.2
Pseudo-distributed mode
The pseudo-distributed mode
with all
daemons running on a single machine. This mode complements the standalone mode
for debugging your code, allowing you to examine memory usage, HDFS input/out-
put issues, and other daemon interactions. Listing 2.1 provides simple XML files to
configure a single server in this mode.
is running Hadoop in a “cluster of one”
Listing 2.1 Example of the three configuration files for pseudo-distributed mode
core-site.xml
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!-- Put site-specific property overrides in this file. -->
<configuration>
<property>
<name>fs.default.name</name>
<value>hdfs://localhost:9000</value>
<description>The name of the default file system. A URI whose
scheme and authority determine the FileSystem implementation.
</description>
</property>
</configuration>
mapred-site.xml
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<!-- Put site-specific property overrides in this file. -->
<configuration>
<property>
<name>mapred.job.tracker</name>
<value>localhost:9001</value>
<description>The host and port that the MapReduce job tracker runs
at.</description>
</property>
</configuration>
hdfs-site.xml
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
