Big Data/YARN

YARN (Yet Another Resource Negotiator) is a cluster management system. It has been part of Apache Hadoop since v2.0.

With the help of YARN arbitrary applications can be executed on a Hadoop cluster. Therefore, the application has to consist of one application master and an arbitrary number of containers. Latter are responsible for the execution of the application whereas the application master requests container and monitors their progress and status.

In order to execute these applications, YARN consists of two component types:
 * 1) The ResourceManager is unique for a complete cluster. Its main task is granting the requested resources and balancing the load of the cluster. Furthermore, it starts the application master initially and restarts it in case of a failure.
 * 2) On each computing node, one NodeManager is executed. It starts and monitors the containers assigned to it as well as the usage of its resources, i.e., CPU usage and memory consumption.