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Explain what is JobTracker in Hadoop? What are the actions followed by Hadoop?

+1 vote
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Explain what is JobTracker in Hadoop? What are the actions followed by Hadoop?
posted Nov 18, 2014 by Amit Kumar Pandey

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1 Answer

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In Hadoop for submitting and tracking MapReduce jobs, JobTracker is used. Job tracker run on its own JVM process

Hadoop performs following actions in Hadoop:

  1. Client application submit jobs to the job tracker
  2. JobTracker communicates to the Namemode to determine data location
  3. Near the data or with available slots JobTracker locates TaskTracker nodes
  4. On chosen TaskTracker Nodes, it submits the work
  5. When a task fails, Job tracker notify and decides what to do then.
  6. The TaskTracker nodes are monitored by JobTracker
answer Dec 2, 2014 by Kali Mishra
Similar Questions
+1 vote

I use Hadoop 2.2 and I want to run MapReduce web UI. So I visit following url: http://x.x.x.x:50030/jobtracker.jsp

Unable to connect Firefox can't establish a connection to the server at x.x.x.x:50030. Where am I wrong?

+2 votes

we want to set the heartbeat timout for a tasktracker.

If the tasktracker does not send heartbeats for 60 seconds he should be marked as lost. I found the parameter mapreduce.jobtracker.expire.trackers.interval which sounds right to me.

I defined

mapreduce.jobtracker.expire.trackers.interval 60000

in the mapred-site.xml on all servers and restarted the jobtracker and all tasktrackers.

I started a benchmark "hadoop jar hadoop-examples.jar randomwriter rand" and every tasktracker gets 2 jobs. It is a small test environment.

On one tasktracker i stopped the network. On the jobtracker i could see the "Seconds since heartbeat"
increasing. But after 60 seconds the tasktracker was still in the overview. Even in the log of the jobtracker I found nothing.

After over 600 seconds i found the message

org.apache.hadoop.mapred.JobTracker: Lost tracker .....

And the tasktracker wasn't shown any more on the jobtracker. Isn't this the right setting?

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