NodeManager is a component of the YARN (Yet Another Resource Negotiator) framework that is responsible for managing the resources (CPU, memory, disk, network) of an individual node in a Hadoop cluster. It is installed on every node in the cluster and runs as a daemon process.
The NodeManager is responsible for launching and monitoring containers, which are isolated and resource-controlled execution environments for running application processes. When a new application is submitted to the cluster, the ResourceManager determines which NodeManager has available resources and instructs it to launch a container for the application. The NodeManager then launches the container on the node, sets up the execution environment, and monitors its resource usage. If the application completes or fails, the NodeManager reports the status back to the ResourceManager.
In addition to container management, the NodeManager also performs other tasks such as managing log files, handling node health checks, and reporting resource usage back to the ResourceManager.
The NodeManager works closely with other components of the Hadoop ecosystem, such as the ResourceManager and the ApplicationMaster, to provide a scalable and efficient resource management system for running distributed applications in a Hadoop cluster.
Overall, the NodeManager plays a critical role in managing the resources of individual nodes in a Hadoop cluster, enabling efficient and scalable execution of distributed applications.