Database Reference
In-Depth Information
Figure 6-15.
The TaskTracker web portal
The
Running tasks
section of the TaskTracker is populated only if a job (which comprises one or more tasks) is
in execution at that point of time. If any MapReduce job is running in the cluster, this section will show the details of
each of the Map and Reduce tasks, as shown in Figure
6-16
.
Figure 6-16.
The running tasks in TaskTracker
While the JobTracker or the MapReduce service tracker is the master monitoring the overall execution of a
MapReduce job, the TaskTrackers manage the execution of individual tasks on each slave node. Another important
responsibility of the TaskTracker is to constantly communicate with the JobTracker. If the JobTracker fails to receive a
heartbeat from a TaskTracker within a specified amount of time, it will assume the TaskTracker has crashed and will
resubmit the corresponding tasks to other nodes in the cluster.
HDInsight Windows Services
In traditional Hadoop, each process like the namenode, datanode, and so on are known as
daemons
, which stands
for
Disk and Execution Monitor
. In simple terms, a daemon is a long-running background process that answers
requests for services. In the Windows environment, they are called
services
. Windows provides a centralized way to
