Database Reference
In-Depth Information
Tasktracker
The
tasktracker
daemon is a daemon that accepts tasks (map, reduce, and shuffle) from
the jobtracker daemon. The tasktracker daemon is the daemon that performs the actual
tasks during a MapReduce operation. The tasktracker daemon sends a heartbeat message to
jobtracker, periodically, to notify the jobtracker daemon that it is alive. Along with the
heartbeat, it also sends the free slots available within it, to process tasks. The tasktracker
daemon starts and monitors the map, and reduces tasks and sends progress/status informa-
tion back to the jobtracker daemon.
In small clusters, the namenode and jobtracker daemons reside on the same node. However,
in larger clusters, there are dedicated nodes for the namenode and jobtracker daemons. This
can be easily understood from the following diagram:
In a Hadoop cluster, these daemons can be monitored via specific URLs using a browser.
The specific URLs are of the
http://<serveraddress>:port_number
type.
