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The Ultimate Cheat Sheet On Hadoop

Top 20 frequently asked questions to test your Hadoop knowledge given in the below Hadoop cheat sheet. Try finding your own answers and match the answers given here.




Question #1 

You have written a MapReduce job that will process 500 million input records and generate 500 million key-value pairs. The data is not uniformly distributed. Your MapReduce job will create a significant amount of intermediate data that it needs to transfer between mappers and reducers which is a potential bottleneck. A custom implementation of which of the following interfaces is most likely to reduce the amount of intermediate data transferred across the network?



A. Writable
B. WritableComparable
C. InputFormat
D. OutputFormat
E. Combiner
F. Partitioner
Ans: e




Question #2 

Where is Hive metastore stored by default ?


A. In HDFS
B. In client machine in the form of a flat file.
C. In client machine in a derby database
D. In lib directory of HADOOP_HOME, and requires HADOOP_CLASSPATH to be modified.
Ans: c




Question…

Oozie - Concepts And Architecture

Oozie is a workflow/coordination system that you can use to manage Apache Hadoop jobs. It is one of the main components of Oozie is the Oozie server — a web application that runs in a Java servlet container (the standard Oozie distribution is using Tomcat).

Oozie is a workflow management-server that works on the Oozie server.

Role of Oozie in Workflow Management in Hadoop Jobs

  1. This server supports reading and executing Workflows, Coordinators, Bundles, and SLA definitions. It implements a set of remote Web Services APIs that can be invoked from Oozie client components and third-party applications.
  2. Add a note where the execution of the server leverages a customizable database.
  3. This database contains Workflow, Coordinator, Bundle, and SLA definitions, as well as execution states and process variables.
  4. The list of currently supported databases includes MySQL, Oracle, and Apache Derby. The Oozie shared library component is located in the Oozie HOME directory and contains code used by the Oozie execution.

Oozie Architecture

oozie architecture


How to work with Oozie in Hadoop Framework

Oozie provides a command-line interface (CLI) that is based on a client component, which is a thin Java wrapper around Oozie Web Services APIs.

These APIs can also be used from third-party applications that have sufficient permissions.
A single Oozie server implements all four functional Oozie components:
  • Oozie Workflow 
  • Oozie Coordinator 
  • Oozie Bundle 
  • Oozie SLA 
  • Oozie server is described in this chapter, starting with what Oozie Workflow is and how you can use it.

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