Database Reference
In-Depth Information
Jobtracker
The
jobtracker
daemon is responsible for accepting job requests from a client and
scheduling/assigning tasktrackers with tasks to be performed. The jobtracker daemon tries
to assign tasks to the tasktracker daemon on the datanode daemon where the data to be pro-
cessed is stored. This feature is called
data locality
. If that is not possible, it will at least
try to assign tasks to tasktrackers within the same physical server rack. If for some reason
the node hosting the datanode and tasktracker daemons fails, the jobtracker daemon assigns
the task to another tasktracker daemon where the replica of the data exists. This is possible
because of the replication factor configuration for HDFS where the data blocks are replic-
ated across multiple datanodes. This ensures that the job does not fail even if a node fails
within the cluster.
