Which MapReduce v2 (MR2/YARN) daemon is a per-machine slave responsible for launching
application containers and monitoring application resources usage?

A.
JobTracker

B.
ResourceManager

C.
ApplicationMaster

D.
NodeManager

E.
ApplicationMasterService

F.
TaskTracker

Explanation:
The fundamental idea of MRv2 (YARN) is to split up the two major functionalities of
the JobTracker, resource management and job scheduling/monitoring, into separate daemons.
The idea is to have a global ResourceManager (RM) and per-application ApplicationMaster (AM).
Note:Let’s walk through an application execution sequence:
1.A client program submits the application, including the necessary specifications to launch the
application-specific ApplicationMaster itself.
2.The ResourceManager assumes the responsibility to negotiate a specified container in which to
start the ApplicationMaster and then launches the ApplicationMaster.
3.The ApplicationMaster, on boot-up, registers with the ResourceManager – the registration allows
the client program to query the ResourceManager for details, which allow it todirectly
communicate with its own ApplicationMaster.
4.During normal operation the ApplicationMaster negotiates appropriate resource containers via
the resource-request protocol.
5.On successful container allocations, the ApplicationMaster launches the container by providing
the container launch specification to the NodeManager. The launch specification, typically,
includes the necessary information to allow the container to communicate with the
ApplicationMaster itself.

6.The application code executing within the container then provides necessary information
(progress, status etc.) to its ApplicationMaster via an application-specific protocol.
7.During the application execution, the client that submitted the program communicates directly
with the ApplicationMaster to get status, progress updates etc. via an application-specific protocol.
8.Once the application is complete, and all necessary work has been finished, the
ApplicationMaster deregisters with the ResourceManager and shuts down, allowing its own
container to be repurposed.
Reference:
Apache Hadoop YARN – Concepts & Applications