Book Image

Learning YARN

By : Akhil Arora, Shrey Mehrotra, Shreyank Gupta
Book Image

Learning YARN

By: Akhil Arora, Shrey Mehrotra, Shreyank Gupta

Overview of this book

Today enterprises generate huge volumes of data. In order to provide effective services and to make smarter and more intelligent decisions from these huge volumes of data, enterprises use big-data analytics. In recent years, Hadoop has been used for massive data storage and efficient distributed processing of data. The Yet Another Resource Negotiator (YARN) framework solves the design problems related to resource management faced by the Hadoop 1.x framework by providing a more scalable, efficient, flexible, and highly available resource management framework for distributed data processing. This book starts with an overview of the YARN features and explains how YARN provides a business solution for growing big data needs. You will learn to provision and manage single, as well as multi-node, Hadoop-YARN clusters in the easiest way. You will walk through the YARN administration, life cycle management, application execution, REST APIs, schedulers, security framework and so on. You will gain insights about the YARN components and features such as ResourceManager, NodeManager, ApplicationMaster, Container, Timeline Server, High Availability, Resource Localisation and so on. The book explains Hadoop-YARN commands and the configurations of components and explores topics such as High Availability, Resource Localization and Log aggregation. You will then be ready to develop your own ApplicationMaster and execute it over a Hadoop-YARN cluster. Towards the end of the book, you will learn about the security architecture and integration of YARN with big data technologies like Spark and Storm. This book promises conceptual as well as practical knowledge of resource management using YARN.
Table of Contents (20 chapters)
Learning YARN
About the Authors
About the Reviewers

Monitoring NodeManager's health

NodeManager is a per-node daemon running on all the slave nodes of the cluster. All the NodeManager nodes are worker nodes that perform application execution. For efficient scheduling, it is important for the ResourceManager to monitor the health of these nodes. Health may include memory, CPU, network usage, and so on. The ResourceManager daemon will not schedule any new application execution requests to an unhealthy NodeManager.

The health checker script

YARN defines a mechanism to monitor health of a node using a script. An administrator needs to define a shell script to monitor the node. If the script returns ERROR as the first word in any of the output lines, then the ResourceManager marks the node as UNHEALTHY.

A sample script to check the memory usage of a node is written next. It checks the current memory usage and if the memory usage is greater than 95%, it prints an error message. You need to create a shell script such as and change...