Hadoop

CCA131 – Exam Answers Validation Steps

In this post, I’ll explain some of the ways to validate the problems you’ve solved in the exam. Using this steps, you can ensure that the you’ve solved the problems as expected and avoid shocks/surprises in the exam result.

When you complete the exam before the alloted time and if you have free time of 10+ minutes, then you can go through all the problems/solutions once and validate.

  • Check the permissions of the files and folders.

Some of the exercises which involves creating, generating, copying files/folders are benchmarking, map reduce jobs, distcp, snapshots, etc.

The expected output would’ve been given as ensure the files are present in the mentioned directory with specified permissions.

In your validation, first confirm the filesystem whether it should be created in local filesysten or HDFS. If you’re in doubt, put it in both file systems.

Second, ‘ls -l’ the files/directory and verify the files permissions, ownership, group ownership, ACLs etc. If there is any missing permissions, ownerships,  do chmod/chown accordingly.

For copying files to specific directory, always prefer to use “mv” command or “cp -p” which preserve permissions and timestamps.

 

  • Verify the roles of the hosts

For problems involving adding a service, roles, you’d ve added them to the respective hosts as given in the problem.

During validation, go to CM – Hosts – Roles section and check the roles of the each nodes.

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Ensure that the roles are assigned as per the problems specifications.

 

  • Stale configurations

After making configuring changes to the service, you should deploy the client configuration.

stale

If any service is showing stale configuration, restart/refresh it right away. Your answer will be marked incorrect, if services show stale configuration at the end of the exam.

 

  • Configuring Services

Once the service is configured, go to the service configuration and search for the property which you modified.

It should show the configured value, if it’s not then you haven’t make the changes properly, so modify it again and deploy client configuration.

 

  • Rerunning jobs and output files

When you got the failed mapreduce job running successfully and generates output, then you’re all good. In case if you want to re run it again, then move the previous outputs to different directory.

Some jobs will fail if the output directory already contains files, so it’s better to move it. If in case, the jobs fail during rerun and you’re running out of time, you can move the old outputs back to the same output directory.

 

Thus we covered how to validate some of the problems at the end of the exam.

Use the comments section below to post your doubts, questions and feedback.

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