What is MRUnit testing?

MRUnit is a JUnit-based Java library that allows us to unit test Hadoop MapReduce programs. This makes it easy to develop as well as to maintain Hadoop MapReduce code bases. MRUnit supports testing Mappers and Reducers separately as well as testing MapReduce computations as a whole.

How does MapReduce work?

MapReduce facilitates concurrent processing by splitting petabytes of data into smaller chunks, and processing them in parallel on Hadoop commodity servers. In the end, it aggregates all the data from multiple servers to return a consolidated output back to the application.

What is classic MapReduce?

MapReduce makes the guarantee that the input to every reducer is sorted by key. The process by which the system performs the sort—and transfers the map outputs to the reducers as inputs—is known as the shuffle. Each map task has a circular memory buffer that it writes the output to.

What is Hadoop MapReduce?

Hadoop MapReduce is a software framework for easily writing applications which process vast amounts of data (multi-terabyte data-sets) in-parallel on large clusters (thousands of nodes) of commodity hardware in a reliable, fault-tolerant manner.

What is difference between Hadoop and MapReduce?

The Apache Hadoop is an eco-system which provides an environment which is reliable, scalable and ready for distributed computing. MapReduce is a submodule of this project which is a programming model and is used to process huge datasets which sits on HDFS (Hadoop distributed file system).

What is difference between cloud and Hadoop?

Hadoop is an ‘ecosystem’ of open source software projects which allow cheap computing which is well distributed on industry-standard hardware. On the other hand, cloud computing is a model where processing and storage resources can be accessed from any location via the internet.

Is Hadoop a PaaS?

We refer to this as Hadoop-as-a-Service (HaaS), a sub-category of Platform-as-a-Service (PaaS). Running Hadoop as a managed cloud-based service is not a cheap proposition but it does save money over buying large numbers of clusters.

Which is better Hadoop or cloud computing?

What is mrunit testing?

MRUnit is a testing framework that lets you test and debug Map Reduce jobs in isolation without spinning up a Hadoop cluster. In this blog post we will cover various features of MRUnit by walking through a simple MapReduce job.

How do I use mrunit to test MapReduce?

MRUnit provides a fluent API to support this use case. You write the test for the reduce exactly the same way. Finally you can use MapReduceDriver to test your Mapper, Combiner and Reducer together as a single job. You can also pass multiple key value pairs as input to your job.

What are the three key classes in mrunits?

Three key classes in MRUnits are MapDriver for Mapper Testing, ReduceDriver for Reducer Testing and MapReduceDriver for end to end MapReduce Job testing. This is how we will setup the Test Class.