The ResourceManager is the central authority of the Yarn cluster. It has two main components:
See Yarn - Yarn UI (ResourceManager UI)
Conf: yarn.resourcemanager.webapp.address
for application submissions. ie The address of the applications manager interface
Conf: yarn.resourcemanager.address
See Scheduler port
YARN supports the notion of resource reservation via the ReservationSystem, a component that allows users to specify a profile of resources over-time and temporal constraints (e.g., deadlines), and reserve resources to ensure the predictable execution of important jobs.
Restart is a feature that allow him to keep functioning across restarts and also makes the down-time invisible to end-users.