Rack Awareness!

[Sugandha Naolekar]

Hello!

**************************************************************************************
Below is the python script I have written::

#!/usr/bin/env python

'''
This script used by hadoop to determine network/rack topology.  It
should be specified in hadoop-site.xml via topology.script.file.name
Property.

<property>
  name>topology.script.file.name</name>
 <value>/home/hadoop/topology.py</value>
</property>
'''

import sys
from string import join

DEFAULT_RACK = '/default/rack0';

RACK_MAP =
{
    '10.20.220.35' : '/jobsec/rack1',
    '10.20.220.78' : '/jobsec/rack1',
    '10.20.220.71' : '/jobsec/rack1',

    '10.20.220.74' : '/jobsec/rack2',
}

if len(sys.argv)==1:
     print DEFAULT_RACK
else:
     print join([RACK_MAP.get(i, DEFAULT_RACK) for i in sys.argv[1:]]," ")

***************************************************************************************
I have to configure my 6 node cluster in which 4 r d datanodes and the other
2 are playing NN,JT and sec.NN roles. The m/c playing JT is also Sec. NN.
Now, i want to configure 3 DN's in rack 1 of JT and the 4th DN in rack2 of
JT.
**************************************************************************************

Also, the values of corresponding tags is also set in site-sml file as::

<property>
  <name>topology.node.switch.mapping.impl</name>
  <value>org.apache.hadoop.net.ScriptBasedMapping</value>
  <description> The default implementation of the DNSToSwitchMapping. It
    invokes a script specified in topology.script.file.name to resolve
    node names. If the value for topology.script.file.name is not set, the
    default value of DEFAULT_RACK is returned for all node names.
  </description>
</property>

<property>
  <name>topology.script.file.name</name>
  <value>/home/hadoop/Softwares/hadoop-0.19.0/conf/test.py</value>
  <description> The script name that should be invoked to resolve DNS names
to
    NetworkTopology names. Example: the script would take host.foo.bar as an
    argument, and return /rack1 as the output.
  </description>
</property>

<property>
  <name>topology.script.number.args</name>
  <value>10</value>
  <description> The max number of args that the script configured with
    topology.script.file.name should be run with. Each arg is an
    IP address.
  </description>
</property>

Here, test.py is the python script file name.

*****************************************************

Now, the moment I start or invoke namenode daemon, this file gets invoked
automatically? What do I do to acheive my purpose...The aove things are
correct(files and scripsts and tags?) how to chk the rack status of
machines..and special command? PLease do help me out!

-- 
Regards!
Sugandha