Hadoop Seminar Report

Hadoop Framework
JJMCOE(2015-16) Page 1
Dr. J. J. Magdum Trust’s
Dr. J. J. Magdum College of Engineering, Jaysingpur
Department of Information Technology
A
SEMINAR REPORT
ON
“Hadoop FrameWork”
In the partial fulfilmentof the requirementsof Seminar report for Semester VI of Third Year
of Engineering in Information Technology Department proposed by Shivaji University, Kolhapur
SubmittedBy
Kulkarni Bhushan Prakash 13IT206
Under the guidance
Of
Prof. T.A.Mulla
Shivaji University, Kolhapur
2015-16

Hadoop Framework
Contents Page No.
1) Acknowledgement i
2) Abstract ii
3) List of Figures iii
4) Chapter1 –
Introduction of Hadoop 1
5) Chapter 2-
History of Hadoop 5
6) Chapter 3-
3.1 MapReduce 8
3.2 Programming Model 9
3.3 Map 10
3.4 Reduce 11
3.5 HDFS 12
3.6 HDFS Concepts 14
3.7Hadoop File System 17
7) Chapter 4-
4.1 Applications of Hadoop 20
8) Chapter 5-
5.1 Conclusion 23
9) Reference 24
Index

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CHAPTER 1:
INTRODUCTION TO
HADOOP

Hadoop Framework
Chapter 1:
Introduction to HADOOP
Today, we’re surrounded by data. People upload videos, take pictures on their cell phones,
text friends, update their Facebook status, leave comments around the web, click on ads, and
so forth. Machines, too, are generating and keeping more and more data.
The exponential growth of data first presented challenges to cutting-edge businesses such
as Google, Yahoo, Amazon, and Microsoft. They needed to go through terabytes and
petabytes of data to figure out which websites were popular, what books were in demand, and
what kinds of ads appealed to people. Existing tools were becoming inadequate to process
such large data sets. Google was the first to publicize MapReduce—a system they had used to
scale their data processing needs.
This system aroused a lot of interest because many other businesses were facing similar
scaling challenges, and it wasn’t feasible for everyone to reinvent their own proprietary tool.
Doug Cutting saw an opportunity and led the charge to develop an open source version of this
MapReduce system called Hadoop. Soon after, Yahoo and others rallied around to support
this effort. Today, Hadoop is a core part of the computing infrastructure for many web
companies, such as Yahoo, Facebook, LinkedIn, and Twitter.
Hadoop is an open source framework for writing and running distributed applications that
process large amounts of data. Distributed computing is a wide and varied field, but the key
distinctions of Hadoop are that it is
■ Accessible—Hadoop runs on large clusters of commodity machines or on cloud
computing services such as Amazon’s Elastic Compute Cloud (EC2 ).
■ Robust—Because it is intended to run on commodity hardware, Hadoop is
architected with the assumption of frequent hardware malfunctions. It can gracefully handle
most such failures.
■ Scalable—Hadoop scales linearly to handle larger data by adding more nodes to the
cluster.
■ Simple—Hadoop allows users to quickly write efficient parallel code.

Hadoop Framework
Hadoop’s accessibility and simplicity give it an edge over writing and running large
distributed programs. Even college students can quickly and cheaply create their own Hadoop
cluster. On the other hand, its robustness and scalability make it suitable for even the most
demanding jobs at Yahoo and Facebook.

Hadoop Framework
CHAPTER 2:
HISTORY OF HADOOP

Hadoop Framework
Chapter 2:
History of HADOOP
Hadoop was created by Doug Cutting, the creator of Apache Lucene, the widely used text
search library. Hadoop has its origins in Apache Nutch, an open source web search engine,
itself a part of the Lucene project.
2.1 The Origin of the Name “Hadoop”:
The name Hadoop is not an acronym; it’s a made-up name. The project’s creator, Doug
Cutting, explains how the name came about:
The name my kid gave a stuffed yellow elephant. Short, relatively easy to spell and
pronounce, meaningless, and not used elsewhere: those are my naming criteria. Kids are
good at generating such. Googol is a kid’s term.
Subprojects and “contrib” modules in Hadoop also tend to have names that are unrelated
to their function, often with an elephant or other animal theme (“Pig,” for example). Smaller
components are given more descriptive (and therefore more mundane) names. This is a good
principle, as it means you can generally work out what something does from its name. For
example, the jobtracker keeps track of MapReduce jobs.
Building a web search engine from scratch was an ambitious goal, for not only is the
software required to crawl and index websites complex to write, but it is also a challenge to
run without a dedicated operations team, since there are so many moving parts. It’s expensive
too: Mike Cafarella and Doug Cutting estimated a system supporting a 1- billion-page index
would cost around half a million dollars in hardware, with a monthly running cost of $30,000.
Nevertheless, they believed it was a worthy goal, as it would open up and ultimately
democratize search engine algorithms. Nutch was started in 2002, and a working crawler and
search system quickly emerged.
However, they realized that their architecture wouldn’t scale to the billions of pages on the
Web. Help was at hand with the publication of a paper in 2003 that described the architecture
of Google’s distributed filesystem, called GFS, which was being used in production at
Google.# GFS, or something like it, would solve their storage needs for the very large files

Hadoop Framework
generated as a part of the web crawl and indexing process. In particular, GFS would free up
time being spent on administrative tasks such as managing storage nodes. In 2004, they set
about writing an open source implementation, the Nutch Distributed Filesystem (NDFS).
In 2004, Google published the paper that introduced MapReduce to the world. Early in
2005, the Nutch developers had a working MapReduce implementation in Nutch, and by the
middle of that year all the major Nutch algorithms had been ported to run using MapReduce
and NDFS. NDFS and the MapReduce implementation in Nutch were applicable beyond the
realm of search, and in February 2006 they moved out of Nutch to form an independent
subproject of Lucene called Hadoop. At around the same time, Doug Cutting joined Yahoo!,
which provided a dedicated team and the resources to turn Hadoop into a system that ran at
web scale (see sidebar). This was demonstrated in February 2008 when Yahoo! announced
that its production search index was being generated by a 10,000-core Hadoop cluster.†
In January 2008, Hadoop was made its own top-level project at Apache, confirming its
success and its diverse, active community. By this timem Hadoop was being used by many
other companies besides Yahoo!, such as Last.fm, Facebook, and the New York Times.

Hadoop Framework
CHAPTER 3:
KEY TECHNOLOGY

Hadoop Framework
Chapter 3:
Key Technology
The key technology for Hadoop is the MapReduce programming model and Hadoop
Distributed File System. The operation on large data is not possible in serial programming
paradigm. MapReduce do task parallel to accomplish work in less time which is the main aim
of this technology. MapReduce require special file system. In the real scenario , the data
which are in terms on perabyte. To store and maintain this much data on distributed
commodity hardware, Hadoop Distributed File System is invented. It is basically inspired by
Google File System.
3.1 MapReduce
MapReduce is a framework for processing highly distributable problems across huge
datasets using a large number of computers (nodes), collectively referred to as a cluster (if all
nodes use the same hardware) or a grid (if the nodes use different hardware). Computational
processing can occur on data stored either in a filesystem (unstructured) or in a database
(structured).
Figure 1. MapReduce Programming Model
"Map" step: The master node takes the input, partitions it up into smaller sub-problems, and
distributes them to worker nodes. A worker node may do this again in turn, leading to a

Hadoop Framework
multi-level tree structure. The worker node processes the smaller problem, and passes the
answer back to its master node.
"Reduce" step: The master node then collects the answers to all the sub-problems and
combines them in some way to form the output – the answer to the problem it was originally
trying to solve.
MapReduce allows for distributed processing of the map and reduction operations.
Provided each mapping operation is independent of the others, all maps can be performed in
parallel – though in practice it is limited by the number of independent data sources and/or
the number of CPUs near each source. Similarly, a set of 'reducers' can perform the reduction
phase - provided all outputs of the map operation that share the same key are presented to the
same reducer at the same time. While this process can often appear inefficient compared to
algorithms that are more sequential, MapReduce can be applied to significantly larger
datasets than "commodity" servers can handle – a large server farm can use MapReduce to
sort a petabyte of data in only a few hours. The parallelism also offers some possibility of
recovering from partial failure of servers or storage during the operation: if one mapper or
reducer fails, the work can be rescheduled – assuming the input data is still available.
MapReduce is a programming model and an associated implementation for processing
and generating largedata sets. Users specify a map function that processes a key/value pair to
generate a set of intermediate key/value pairs, and a reduce function that merges all
intermediate values associated with the same intermediate key. Many real world tasks are
expressible in this model.
3.2 PROGRAMMING MODEL
The computation takes a set of input key/value pairs, and produces a set of output
key/value pairs. The user of the MapReduce library expresses the computation as two
functions: Map and Reduce. Map, written by the user, takes an input pair and produces a set
of intermediate key/value pairs. The MapReduce library groups together all intermediate
values associatedwith the same intermediate key I and passes them to the Reduce function.
The Reduce function, also written by the user, accepts an intermediate key I and a set of
values for that key. It merges together these values to form a possibly smaller set of values.

Hadoop Framework
Typically just zero or one output value is produced per Reduce invocation. The intermediate
values are supplied to the user's reduce function via an iterator. This allows us to handle lists
of values that are too large to fit in memory.
3.3 MAP
map (in_key, in_value) -> (out_key, intermediate_value) list
Figure:2 Map Technology
Example: Upper-case Mapper
let map(k, v) = emit(k.toUpper(), v.toUpper())
(“foo”, “bar”) --> (“FOO”, “BAR”)
(“Foo”, “other”) -->(“FOO”, “OTHER”)
(“key2”, “data”) --> (“KEY2”, “DATA”)

Hadoop Framework
3.4 REDUCE
reduce (out_key, intermediate_value list) ->out_value list
Figure:3 Reducing Technology
Example: Sum Reducer
let reduce(k, vals)
sum = 0
foreachint v in vals:
sum += v
emit(k, sum)
(“A”, [42, 100, 312]) --> (“A”, 454)
(“B”, [12, 6, -2]) --> (“B”, 16)

Hadoop Framework
Hadoop Map-Reduce 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.
A Map-Reduce job usually splits the input data-set into independent chunks which are
processed by the map tasks in a completely parallel manner. The framework sorts the outputs
of the maps, which are then input to the reduce tasks. Typically both the input and the output
of the job are stored in a file-system. The framework takes care of scheduling tasks,
monitoring them and re-executes the failed tasks.
A MapReducejob is a unit of work that the client wants to be performed: it consists of the
input data, the MapReduce program, and configuration information. Hadoop runs the job by
dividing it into tasks, of which there are two types: map tasks and reduce tasks. There are two
types of nodes that control the job execution process: a jobtrackerand a number of
tasktrackers. The jobtracker coordinates all the jobs run on the system by scheduling tasks to
run on tasktrackers.
Figure 4: HadoopMapReduce
3.5 HDFS (Hadoop Distributed File System)
The Hadoop Distributed File System (HDFS) is a distributed file system designed to run
on commodity hardware. It has many similarities with existing distributed file systems.
However, the differences from other distributed file systems are significant. HDFS is highly
fault-tolerant and is designed to be deployed on low-cost hardware. HDFS provides high

Hadoop Framework
throughput access to application data and is suitable for applications that have large data sets.
HDFS relaxes a few POSIX requirements to enable streaming access to file system data.
HDFS was originally built as infrastructure for the Apache Nutch web search engine project.
HDFS is now an Apache Hadoop subproject.
Figure 5 HDFS Architecture
HDFS has a master/slave architecture. An HDFS cluster consists of a single NameNode, a
master server that manages the file system namespace and regulates access to files by clients.
In addition, there are a number of DataNodes, usually one per node in the cluster, which
manage storage attached to the nodes that they run on. HDFS exposes a file system
namespace and allows user data to be stored in files. Internally, a file is split into one or more
blocks and these blocks are stored in a set of DataNodes. The NameNode executes file
system namespace operations like opening, closing, and renaming files and directories. It also
determines the mapping of blocks to DataNodes. The DataNodes are responsible for serving
read and write requests from the file system’s clients. The DataNodes also perform block
creation, deletion, and replication upon instruction from the NameNode.
The NameNode and DataNode are pieces of software designed to run on commodity
machines. These machines typically run a GNU/Linux operating system (OS). HDFS is built

Hadoop Framework
using the Java language; any machine that supports Java can run the NameNode or the
DataNode software. Usage of the highly portable Java language means that HDFS can be
deployed on a wide range of machines. A typical deployment has a dedicated machine that
runs only the NameNode software. Each of the other machines in the cluster runs one
instance of the DataNode software. The architecture does not preclude running multiple
DataNodes on the same machine but in a real deployment that is rarely the case.
The existence of a single NameNode in a cluster greatly simplifies the architecture of the
system. The NameNode is the arbitrator and repository for all HDFS metadata. The system is
designed in such a way that user data never flows through the NameNode.
Filesystems that manage the storage across a network of machines are called
distributed filesystems. Since they are network-based, all the complications of network
programming kick in, thus making distributed filesystems more complex than regular disk
filesystems. For example, one of the biggest challenges is making the filesystem tolerate node
failure without suffering data loss. Hadoop comes with a distributed filesystem called HDFS,
which stands for HadoopDistributed Filesystem.
HDFS, the Hadoop Distributed File System, is a distributed file system designed to
hold very large amounts of data (terabytes or even petabytes), and provide high-
throughput access to this information. Files are stored in a redundant fashion across
multiple machines to ensure their durability to failure and high availability to very parallel
applications.
3.6 HDFS CONCEPTS
a) Blocks
A disk has a block size, which is the minimum amount of data that it can read or write.
Filesystems for a single disk build on this by dealing with data in blocks, which are an
integral multiple of the disk block size. Filesystem blocks are typically a few kilobytes in
size, while disk blocks are normally 512 bytes. This is generally transparent to the filesystem

Hadoop Framework
user who is simply reading or writing a file—of whatever length. However, there are tools to
do with filesystem maintenance, such as dfand fsck, that operate on the filesystem block
level. HDFS too has the concept of a block, but it is a much larger unit—64 MB by default.
Like in a filesystem for a single disk, files in HDFS are broken into block-sized chunks,
which are stored as independent units. Unlike a filesystem for a single disk, a file in HDFS
that is smaller than a single block does not occupy a full block’s worth of underlying storage.
When unqualified, the term “block” in this book refers to a block in HDFS.
b) Namenodes and Datanodes
A HDFS cluster has two types of node operating in a master-worker pattern: a
namenode(the master) and a number of datanodes(workers). The namenode manages the
filesystem namespace. It maintains the filesystem tree and the metadata for all the files and
directories in the tree. This information is stored persistently on the local disk in the form of
two files: the namespace image and the edit log. The namenode also knows the datanodes on
which all the blocks for a given file are located, however, it does not store block locations
persistently, since this information is reconstructed from datanodes when the system starts. A
client accesses the filesystem on behalf of the user by communicating with the namenode and
datanodes.
Figure 6 HDFS Architecture

Hadoop Framework
The client presents a POSIX-like filesystem interface, so the user code does not need to know
about the namenode and datanode to function. Datanodes are the work horses of the
filesystem. They store and retrieve blocks when they are told to (by clients or the namenode),
and they report back to the namenode periodically with lists of blocks that they are storing.
Without the namenode, the filesystem cannot be used. In fact, if the machine running the
namenode were obliterated, all the files on the filesystem would be lost since there would be
no way of knowing how to reconstruct the files from the blocks on the datanodes. For this
reason, it is important to make the namenode resilient to failure.
c) The File System Namespace
HDFS supports a traditional hierarchical file organization. A user or an application can create
directories and store files inside these directories. The file system namespace hierarchy is
similar to most other existing file systems; one can create and remove files, move a file from
one directory to another, or rename a file. HDFS does not yet implement user quotas or
access permissions. HDFS does not support hard links or soft links. However, the HDFS
architecture does not preclude implementing these features.
d) Data Replication
HDFS is designed to reliably store very large files across machines in a large cluster. It stores
each file as a sequence of blocks; all blocks in a file except the last block are the same size.
The blocks of a file are replicated for fault tolerance. The block size and replication factor are
configurable per file. An application can specify the number of replicas of a file. The
replication factor can be specified at file creation time and can be changed later.
Data replication

Hadoop Framework
3.7 HADOOP FILESYSTEMS
Hadoop has an abstract notion of filesystem, of which HDFS is just one implementation. The
Java abstract class org.apache.hadoop.fs.FileSystem represents a filesystem in Hadoop, and
there are several concrete implementations, which are described in following table.
Local file
fs.LocalFileSystem
A filesystem for a locally
connected disk with client-side
checksums.
Use RawLocalFileSystem for a
local filesystem with no
checksums.
HDFS hdfs hdfs.DistributedFileSystem
Hadoop’s distributed filesystem.
HDFS is designed to work
efficiently in conjunction with
Map-Reduce.
HAR har Fs.HarFileSystem
A filesystem layered on another
filesystem for archiving files.
Hadoop
Archives are typically used for
archiving files in HDFS to reduce
the namenode’s memory usage.
KFS(C
loud
Store)
Kfs fs.kfs.KosmosFileSystem
CloudStore (formerly
Kosmosfilesystem)is a distributed
filesystem like HDFS or Google’s
GFS, written in C++.
FTP ftp fs.ftp.FtpFileSystem
A filesystem backed by an FTP
server.
Table: 8.2 Various HadoopFilesystems

Hadoop Framework
3.8 HADOOP ARCHIVES
HDFS stores small files inefficiently, since each file is stored in a block, and block
metadata is held in memory by the namenode. Thus, a large number of small files can eat up
a lot of memory on the namenode. (Note, however, that small files do not take up any more
disk space than is required to store the raw contents of the file. For example, a 1 MB file
stored with a block size of 128 MB uses 1 MB of disk space, not 128 MB.) Hadoop Archives,
or HAR files, are a file archiving facility that packs files into HDFS blocks more efficiently,
thereby reducing namenode memory usage while still allowing transparent access to files. In
particular, Hadoop Archives can be used as input to MapReduce.

Hadoop Framework
CHAPTER 4
APPLICATIONS OF
HADOOP

Hadoop Framework
Chapter 4
Applications of Hadoop
4.1.
Amazon S3 (Simple Storage Service) is a data storage service. You are billed monthly for
storage and data transfer. Transfer between S3 and AmazonEC2 is free. This makes use of S3
attractive for Hadoop users who run clusters on EC2.
Hadoop provides two filesystems that use S3 :-
1. S3 Native FileSystem (URI scheme: s3n)
2. S3 Block FileSystem (URI scheme: s3)
4.2.
Facebook’s engineering team has posted some details on the tools it’s using to analyze the
huge data sets it collects. One of the main tools it uses is Hadoop that makes it easier to
analyze vast amounts of data.
Some interesting tidbits from the post:
Facebook has multiple Hadoop clusters deployed now - with the biggest having about 2500
cpu cores and 1 PetaByte of disk space. They are loading over 250 gigabytes of compressed
data (over 2 terabytes uncompressed) into the Hadoop file system every day and have
hundreds of jobs running each day against these data sets. The list of projects that are using
this infrastructure has proliferated - from those generating mundane statistics about site
usage, to others being used to fight spam and determine application quality.

Hadoop Framework
 Over time, we have added classic data warehouse features like partitioning,
sampling and indexing to this environment. This in-house data warehousing
layer over Hadoop is called Hive.
4.3.
Yahoo! recently launched the world's largest Apache Hadoop production application.
The Yahoo! Search Webmap is a Hadoop application that runs on a more than
10,000 core Linux cluster and produces data that is now used in every Yahoo! Web
search query.
The Webmap build starts with every Web page crawled by Yahoo! and produces a
database of all known Web pages and sites on the internet and a vast array of data
about every page and site. This derived data feeds the Machine Learned Ranking
algorithms at the heart of Yahoo! Search.
Some Webmap size data:Number of links between pages in the index: roughly 1
trillion links
Size of output: over 300 TB, compressed!
Number of cores used to run a single Map-Reduce job: over 10,000
Raw disk used in the production cluster: over 5 Petabytes

Hadoop Framework
CHAPTER 5:
CONCLUSION

Hadoop Framework
Chapter 5
CONCLUSION
• By the above description we can understand the need of Big Data in future, so
Hadoop can be the best of maintenance and efficient implementation of large
data.
• This technology has bright future scope because day by day need of data
would increase and security issues also the major point.In now a days many
Multinational organisations are prefer Hadoop over RDBMS.
• So major companies like facebook amazon, yahoo, linkedIn etc. are adapting
Hadoop and in future there can be many names in the list.
• Hence Hadoop Technology is the best appropriate approach for handling the
large data in smart way and its future is bright…

Hadoop Framework
REFERENCES:

Hadoop Framework
References:
http://www.cloudera.com/hadoop-training-thinking-at-scale
http://developer.yahoo.com/hadoop/tutorial/module1.html
http://hadoop.apache.org/core/docs/current/api/
http://hadoop.apache.org/core/version_control.html
http://wikipidea.in/apachehadoop.com

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