How Hadoop YARN Node Manager Works

Conceptually, the NodeManager is more of generic and efficient version ofTaskTracker of Hadoop1 architecture which is more flexible and efficient than TaskTracker. In contrast to fixed number of slots for map and reduce tasks in MRV1,the NodeManager of MRV2 has a number of dynamically created resource containers. There is no hardcoded split into Map and Reduce slots as in MRV1.The container refers to collection of resources such as memory,CPU,disk and network IO.The number of containers on a node is the product of configuration parameter and the total amount of node resources.

The NodeManager is the per-machine/per-node framework agent who is responsible for containers, monitoring their resource usage and reporting the same to theResourceManager. Overseeing container’s life cycle management, NodeManager also tracks the health of the node on which it is running, controls auxiliary services which different YARN applications may exploit at any point of time. NodeManager can execute any computations that make sense toApplicationMaster just by creating the container for each task.

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