Not able to see racks in reports

Question

I made changes for coresite.xml and etc /hosts and restarted the hadoop demons. When I tired to check the hadoop report not able to see the racks in the report. Can you please help me?

Answer 1

Seems like rack awareness is not configure. 

Try to follow the below-given steps to configure rack awareness:

1. Stop all the daemons running.

$ ./stop-all.sh

2. Create a topology data file anywhere in Master node (NameNode)

$ vi topology.data

3. Mention your slave nodes ( DataNodes) relative to their rack into topology.data- as follows:

192.168.1.4 /rack1

192.168.1.5 /rack1

192.168.1.6 /rack2

192.168.1.7 /rack2

192.168.1.8 /rack3

5. Create a topology.sh script file

#!/bin/bash

while [ $# -gt 0 ] ; do

   nodeArg=$1

   exec< /home/hadoop/topology.data

   result=""

   while read line ; do

       ar=( $line )

       if [ "${ar[0]}" = "$nodeArg" ] ; then

       result="${ar[1]}"

       fi

   done

   shift

   if [ -z "$result" ]; then

     echo -n "/default/rack "

    else

     echo -n "$result "

   fi

   done

6. Add the below property into hdfs-site.xml of Master node.

<property>

<name>topology.script.file.name</name>

<value>/home/hadoop/topology.sh</value>

</property>

7. Start the Hadoop cluster command: ./start-dfs.sh

8. Check the Hadoop admin report to see if the cluster is aware of the rack.

$ ​hadoop dfsadmin -report