RE: Configure Rack Numbers

[Brahma Reddy Battula]

Hi Navaz,

you have to configure the following two properties in namenode(after that you 
need to restart the namenode).


<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>/path/to/topo.sh</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>


Example script file.


topo.sh
=======

#!/bin/bash

python <TOPOLOGY_SCRIPT_HOME>/topology.py "$@"


topology.py
===========

import sys
from string import join

DEFAULT_RACK = '/default/rack0';

RACK_MAP = { '208.94.2.10' : '/datacenter1/rack0',
             '1.2.3.4' : '/datacenter1/rack1',
             '1.2.3.5' : '/datacenter1/rack1',
             '1.2.3.6' : '/datacenter1/rack1',

             '10.2.3.4' : '/datacenter1/rack2',
             '10.2.3.4' : '/datacenter1/rack2'
    }

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


Please check the following link for more details.


https://issues.apache.org/jira/secure/attachment/12345251/Rack_aware_HDFS_proposal.pdf




Thanks & Regards

 Brahma Reddy Battula



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________________________________
From: Abdul Navaz [navaz....@gmail.com]
Sent: Monday, November 17, 2014 4:48 AM
To: user@hadoop.apache.org
Subject: Configure Rack Numbers


Hello,

I have hadoop cluster with 9 nodes. All belongs to /default racks. But I want 
the setup something similar to this.

(All are in same subnets)

 Rack 0: DataNode1,Datanode2,DataNode3 and top of rack switch1.
 Rack 1: DataNode4,Datanode5,DataNode6 and top of rack switch2.
 Rack 3: DataNode7,Datanode8,DataNode9 and top of rack switch3.


I am trying to check the Hadoop rack awareness and how it copies the single 
block of data in one rack and replicas in some other rack. I want to analyse 
some network performance from this.

So how can we separate this DNs based on rack numbers. Where can we configure 
this rack numbers and say this DN belongs to this rack number.


Thanks & Regards,

Abdul Navaz