The fundamental idea of YARN is to split up the functionalities of resource management and job scheduling/monitoring into separate daemons.
The idea is to have a global ResourceManager (RM) and per-application ApplicationMaster (AM).
An application is either a single job or a DAG of jobs.
YARN的基本思想是将资源管理和作业调度/监控的功能拆分到单独的守护进程中。
这个想法是有一个全局的ResourceManager（RM）和每个应用程序的ApplicationMaster（AM）。
应用程序可以是单个作业，也可以是作业的DAG。