When someone mentions Hadoop, they generally don’t refer to the core Apache Hadoop project, but instead are referring to its technology along with an ecosystem of other projects that work with Hadoop. It’s just like when someone tells you they are using Linux as their operating system but they mean the thousands of applications that run on the Linux kernel along with it.Core Apache HadoopCore Hadoop is a software platform and framework for distributed computing of data. Hadoop is a long-running system that runs and executes computing tasks akin to a platform. Platforms make it easier for engineers to deploy applications and analytics because they don’t have to work on building the infrastructure from scratch for every task again. Hadoop is a framework in the sense that it provides a layer of abstraction to developers of data applications and data analytics that keeps the intricacies of the system hidden. The core Apache Hadoop project is organized into three major components that provide a foundation for the rest of the ecosystem:
HDFS (Hadoop Distributed File System)
A filesystem that keeps data stored across multiple computers (i.e., in a distributed manner); it is designed to be high throughput (ability to multi task), resilient, and scalable.
YARN (Yet Another Resource Negotiator)
A management framework for Hadoop resources; it keeps the CPU,RAM and disk space being used under check, and tries to ensure smooth running of processing.
A generalized framework for processing and analyzing data in a distributed fashionHDFS can manage and store large amounts of data over hundreds or thousands of individual computers. However, in stark contrast to traditional storage that just stores data (e.g., NetApp or EMC) or supercomputers that just compute things (e.g., Cray), Hadoop allows you to store huge amounts of data as well as process lots of it with YARN and MapReduce.The Hadoop ecosystem The Hadoop ecosystem is a collection of tools and systems that run alongside of or on top of Hadoop. If the tool or system has a purpose outside of Hadoop but Hadoop users can leverage it, it is called running “alongside” Hadoop. Running “on top of” Hadoop means that the tool or system leverages core Hadoop and requires it to work. Nobody maintains an official ecosystem list, and the ecosystem is constantly changing with new tools being coming into the picture and old tools becoming obsolete.Just like Linux distributions, there are several Hadoop distributions that bundle up core technologies into one supportable platform. Vendors such as Cloudera, Hortonworks, Pivotal, and MapR all have distributions. Different tools and services are provided by each vendor along with their distributions, and the right vendor for your company depends on your particular use case and other needs.A typical Hadoop “stack” consists of the Hadoop platform and framework, along with a selection of ecosystem tools chosen for a particular use case, running on top of a cluster of computers.
Source: data science centralHadoop and its ecosystem represent a new way of doing things, as we’ll look at next.Hadoop Masks Being a Distributed SystemHadoop is a distributed system, which means it coordinates the usage of a cluster of multiple computational resources (referred to as servers, computers, or nodes) that communicate over a network. Using distributed systems we can solve problems that cannot be solved by a single computer. A distributed system can store more data than can be stored on just one machine and process data much faster than a single machine can. However, this increases complexity, because the computers in the cluster need to communicate with each other, and the system needs to handle the increased chance of failure inherent in using more machines. These are some of the disadvantages of using a distributed system. We don’t use distributed systems because we want to…we use them because we cannot do without them.Hadoop does a good job of hiding from its users that it is a distributed system by portraying itself as a single system. This makes the life of the user a whole lot easier because he or she can focus on analysis of data part instead of manually coordinating different computers or manually planning for failures.Take a look at this snippet of Hadoop MapReduce code written in Java. Even if you aren’t well versed with Java, you can still look at the code and get a general feel of what’s happening. There is a point to this, I promise.Here’s an example MapReduce job that I wrote in Java to count words.// This block of code defines the behavior of the map phase// This block of code defines the behavior of the reducer phase This code is for word counting, the canonical example for MapReduce. MapReduce can do all sorts of fancy things, but in this relatively simple case it takes a body of text, and it will return the list of words seen in the text along with how many times each of those words was seen.Nowhere in the code is there a mention of how much data is being analyzed or what the size of the cluster is. . The code in the above example could be run over a 10,000 node Hadoop cluster or on a laptop without any modifications. This same code could process 20 petabytes of website text or could process a single email.This makes the code extremely portable, which means that before shipping it can be tested on a developer’s workstation with a sample of data. The code does not need to be changed if the nature or size of the cluster changes later down the road. Also, this abstracts away all of the complexities of a distributed system for the developer, which makes his or her life easier in several ways: opportunities to make errors are reduced, fault tolerance is built in, there is lesser code to write, and so much more — in short. Hadoop has taken off in terms of popularity owing to its accessibility to the average software developer in comparison to previous distributed computing frameworks is one of the main reasons why Hadoop has taken off in terms of popularity.
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