Book Image

Mastering Hadoop 3

By : Chanchal Singh, Manish Kumar
Book Image

Mastering Hadoop 3

By: Chanchal Singh, Manish Kumar

Overview of this book

Apache Hadoop is one of the most popular big data solutions for distributed storage and for processing large chunks of data. With Hadoop 3, Apache promises to provide a high-performance, more fault-tolerant, and highly efficient big data processing platform, with a focus on improved scalability and increased efficiency. With this guide, you’ll understand advanced concepts of the Hadoop ecosystem tool. You’ll learn how Hadoop works internally, study advanced concepts of different ecosystem tools, discover solutions to real-world use cases, and understand how to secure your cluster. It will then walk you through HDFS, YARN, MapReduce, and Hadoop 3 concepts. You’ll be able to address common challenges like using Kafka efficiently, designing low latency, reliable message delivery Kafka systems, and handling high data volumes. As you advance, you’ll discover how to address major challenges when building an enterprise-grade messaging system, and how to use different stream processing systems along with Kafka to fulfil your enterprise goals. By the end of this book, you’ll have a complete understanding of how components in the Hadoop ecosystem are effectively integrated to implement a fast and reliable data pipeline, and you’ll be equipped to tackle a range of real-world problems in data pipelines.
Table of Contents (23 chapters)
Title Page
Dedication
About Packt
Foreword
Contributors
Preface
Index

Quorum Journal Manager (QJM)


NameNode used to be a single point of failure before the release of Hadoop version 2. In Hadoop 1, each cluster consisted of a single NameNode. If this NameNode failed, then the entire cluster would be unavailable. So, until and unless the NameNode service restarted, no one could use the Hadoop cluster. In Hadoop 2, the high availability feature was introduced. It has two NameNodes, one of the NameNodes is in active state while the other NameNode is in standby state. The active NameNode serves the client requests while the standby NameNode maintains synchronization of its state to take over as the active NameNode if the current active NameNode fails. 

There is a Quorum Journal Manager (QJM) runs in each NameNode. The QJM is responsible for communicating with JournalNodes using RPC; for example, sending namespace modifications, that is, edits to JournalNodes, and so on. A JournalNode daemon can run on N machines where N is configurable. A QJM writes edits to the...