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HADOOP - What is a Task Tracker in Hadoop? How many instances of TaskTracker run on a Hadoop Cluster




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asked SRVMTrainings May 18, 2014 12:02 AM  

What is a Task Tracker in Hadoop? How many instances of TaskTracker run on a Hadoop Cluster


           

2 Answers



 
answered By   0  
Task Tracker is a slave node daemon service for running the tasks that job tracker assigns for each node.

One TaskTracker used for processing tasks ( map,shuffle,sort,reduce) recieved from Job Tracked.


A TaskTracker is a slave node daemon in the cluster that accepts tasks (Map, Reduce and Shuffle operations) from a JobTracker. There is only One Task Tracker process run on any hadoop slave node. Task Tracker runs on its own JVM process. Every TaskTracker is configured with a set of slots, these indicate the number of tasks that it can accept. The TaskTracker starts a separate JVM processes to do the actual work (called as Task Instance) this is to ensure that process failure does not take down the task tracker. The TaskTracker monitors these task instances, capturing the output and exit codes. When the Task instances finish, successfully or not, the task tracker notifies the JobTracker. The TaskTrackers also send out heartbeat messages to the JobTracker, usually every few minutes, to reassure the JobTracker that it is still alive. These message also inform the JobTracker of the number of available slots, so the JobTracker can stay up to date with where in the cluster work can be delegated.
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answered By ckreddy   0  
JobTracker is the daemon service for submitting and tracking MapReduce jobs in Hadoop. There is only One Job Tracker process run on any hadoop cluster. Job Tracker runs on its own JVM process. In a typical production cluster its run on a separate machine. Each slave node is configured with job tracker node location. The JobTracker is single point of failure for the Hadoop MapReduce service. If it goes down, all running jobs are halted. JobTracker in Hadoop performs following actions(
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