Big Data Hadoop Interview Questions and Answers



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Top Big Data Hadoop Interview Questions and Answers - 2021 [UPDATED]

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Big Data Hadoop Interview Questions and Answers

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Big Data is relative term. When Data can’t be handle using conventional systems like RDBMS because Data is generating with very high speed, it is known as Big Data.

Since Data is growing rapidly and RDBMS can’t control it, Big Data technologies came into picture.

Big Data have 3 core dimensions: Volume Variety Velocity

Volume: Volume is nothing but amount of data. As Data is growing with high speed, a huge volume of data is getting generated every second.

Variety: So many applications are running nowadays like mobile, mobile sensors etc. Each application is generating data in different variety.

Velocity: This is speed of data getting generated. for example: Every minute, Instagram receives 46,740 new photos. So day by day speed of data generation is getting higher.

There are two more V’s of Big Data. Below are less known V’s: Veracity Value

Veracity: Veracity is nothing but the accuracy of data. Big Data should have some accurate data in order to process it.

Value: Big Data should contain some value to us. Junk Values/Data is not considered as real Big Data.

Hadoop: Hadoop is a project of Apache. This is a framework which is open Source. Hadoop is use for storing Big data and then processing it.

In order to process Big data, we need some framework. Hadoop is an open source framework which is owned by Apache organization. Hadoop is the basic requirement when we think about processing big data.

Big Data will be processed using some framework. This framework is known as Hadoop.

Hadoop Ecosystem is nothing but a combination of various components. Below are the components which comes under Hadoop Ecosystem’s Umbrella: HDFS YARN MapReduce Pig Hive Sqoop, etc.

HDFS: HDFS is known as Hadoop Distributed File System. Like Every System have one file system in order to see/manage files stored, in the same way Hadoop is having HDFS which works in distributed manner.

HDFS is the core component of Hadoop Ecosystem. Since Hadoop is a distributed framework and HDFS is also distributed file system. It is very well compatible with Hadoop.

YARN: YARN is known as Yet Another Resource Manager. This is a project of Apache Hadoop.

YARN is use for managing resources. Jobs are scheduled using YARN in Apache Hadoop.

MapReduce: MapReduce is a programming approach which consist of two steps: Map and Reduce. MapReduce is the core of Apache Hadoop.

MapReduce is a programming approach to process our data. MapReduce is use to process Big Data.

This is a project of Apache. It is a platform using which huge datasets are analyzed. It runs on the top of MapReduce.

Pig is use for the purpose of analyzing huge datasets. Data flow are created using Pig in order to analyze data. Pig Latin language is use for this purpose.

Pig Latin is a script language which is used in Apache Pig to create Data flow in order to analyze data.

Hive is a project of Apache Hadoop. Hive is a dataware software which runs on the top of Hadoop.

Hive works as a storage layer which is used to store structured data. This is very useful and convenient tool for SQL user as Hive use HQL.

HQL is an abbreviation of Hive Query Language. This is designed for those user who are very comfortable with SQL. HQL is use to query structured data into hive.

Sqoop is a short form of SQL to Hadoop. This is basically a command line tool to transfer data between Hadoop and SQL and vice-versa.

Sqoop is a CLI tool which is used to migrate data between RDBMS to Hadoop and vice-versa.

Below are other components of Hadoop Ecosystem: a) HBase b) Oozie c) Zookeeper d) Flume etc.

Hadoop is a framework while HDFS is a file system which works on the top of Hadoop.

below is command: hdfs fs or hdfs dfs

below is command: hdfs fs -mkdir

below is command: hdfs fs -put or hdfs fs -copyfromLocal

below is command: hdfs fs -copyToLocal

below is command: hdfs fs -rm

below is command: hdfs fs -rm

below is command: hdfs fs -cat

FAT, NAS, EXT are the well-known file systems available in market.

below are the basic steps to be done while working with Big Data: Data Ingestion Data Storage Data Processing

Before Big Data came into Picture, our data used to reside into RDBMS. Data Ingestion is a process to move/ingest your data from one place to another place. In the reference of Big Data, Data movement from RDBMS to Hadoop is known as Data Ingestion.

This steps comes into picture after Data Ingestion. Ingested data is stored into different storage layers like: HDFS, Hive tables etc.

Data Processing: Once you have data in HDFS, Data is processed for different purpose. Data can be processed using MapReduce, Hive tables etc.

There are a huge number of source available which generate different types of data. Some Sources generate data which can’t be stored into tables i.e. that data is not in tabular form. Such data is known as Unstructured Data.

HBase, Cassandra, MongoDB are well known storage layers available in market to store unstructured data.

below are most of the well-known and useful features of Hadoop: Open Source Distributed Processing Fault tolerant High available Commodity Hardware

Hadoop is a framework given by Apache. Frameworks which are available for free of cost are known as Open Source.

Data stored in Hadoop is distributed across clusters in order to give better performance and to make data highly available.

Since Data is Highly available in Hadoop. There is very minimum or no chance to lose data as each data is replicated 3 times by default. So Hadoop is known as Highly Fault tolerant framework.

Hadoop stores all data 3 times i.e. it makes 3 copy of each data. This number can be change. By doing this, Hadoop makes data highly available as there is no chance to lose data. If data will not be available on any node, Hadoop will bring data from other node and will provide to client.

Replication factor is the term which is used to decide the number by which each data will be replicated into Hadoop. User can change replication factor according to their need. By default, its value is 3.

prcessing time is high storage limitation stores only the structured data which is in the form of rows and columns cost of hardware is high cost of sofware is high not a open source. we cannot do any customization

Name node is master in hadoop architecture which stores the meta data of data nodes. in hadoop1.x only one name node is used where as in hadoop 2.x 2 name nodes are used. Name node is the sinlge point of failure in hadoop1.x

Data nodes are the slaves which are used to store data/ block of file

3 set in hdfs-site.xml can be set according to data high availability

JT – Job Tracker which assigns jobs to Task trackers. TT- Task tracker which executes the job assigned by JT Secondary name node- its a name node keeps the metadata information of name node. After evry 30 min, the name node info is updated in secondary name node.

kepping atleast one copy of block in another emote tracker

make sure you have a file called simple.txt in a path /home/training/simple.txt $hadoop fs – ls copyFromLocal /home/training/simple.txt /GangBoard_HDFS where GangBoard_HDFS is a directory created in HDFS instead of copyFromLocal we can use put. put and copyFromLocal give the same result.

$hadoop fs – ls copyToLocal /GangBoard_HDFS/simple.txt /home/training Get and copyToLocal give the same result

Hive is tool used for querrying and processing a data. Hive is developed by Facebook and donated to ApacheSoftwareFoundation. Hives is to store mostly a structured data.

all metadata will be stored in meta store database a default directory will be created in /hive/usr/warehouse with the table name.

Managed/internal table Here once the table gets deleted both meta data and actual data is deleted –>external table Here once the table gets deleted only the mata data gets deleted but not the actual data.

hive>create table student(sname string, sid int) row format delimited fileds terminated by ‘,’; //hands on hive>describe student;

hive>load data local inpath /home/training/simple.txt into table student; //hands on hive> select * from student;

without location hive>create external table student(sname string, sid int) row format delimited fileds terminated by ‘,’; hive>load data local inpath /home/training/simple.txt into table student; *With Location hive>create external table student(sname string, sid int) row format delimited fileds terminated by ‘,’ location /GangBoard_HDFS; Here no need of load command

hive>create table student(sname string, sid int) partitioned by(int year) row format delimited fileds terminated by ‘,’;

hive>load data local inpath /home/training/simple2018.txt into table student partition(year=2018);

create a normal table hive>create table student(sname string, sid int) row format delimited fileds terminated by ‘,’; –>load data hive>load data local inpath /home/training/studnetall.txt into table student ; –>create a partitioned table hive>create table student_partition(sname string, sid int) partitioned by(int year) row format delimited fileds terminated by ‘,’; –>set partitions hive>set hive.exec.dynamic.partition.mode = nonstrict; –>insert data hive>insert into table student_partition select * from student; –>drop normal table hive>drop table student;

Pig is an abstraction over map reduce. It is a tool used to deal with huge amount of structured and semi structed data.

its a small piece of data or a filed eg: ‘shilpa’

ordered set of filed (shilpa, 100)

un-ordered set of tuples eg.{(sh,1),(ww,ww)}

bag of tuples

its a distributed column oriented database built on top of hadoop file system it is horizontally scalable

RDMBS is schema based hbase is not RDMBS only structured data hbase structured and semi structured data. RDMBS involves transactions Hbase no transactions

collection of rows

collection of column families

collection of columns

collection of key value pair

hbase shell hbase>start

create alter drop drop_all exists list enable is_enabled? disable is_disbled?

put get scan delete delete_all

Name node data node secondary NN JT TT Hmaster HRegionServer HQuorumPeer

create ’emp’, ‘cf1?,’cf2’

scan ’emp’


sqoop is an interface/tool between RDBMS and HDFS to importa nd export data

map reduce is a data processing technique for distributed computng base on java map stage reduce stage

facebook adobe yahoo twitter ebay

$>sqoop-import –connect jdbc:mysql://localhost/GangBoard username hadoop password hadoop table emp target_dir sqp_dir fields_terminated_by ‘,’ m 1

it is an object having the information about hadoop configuration

To start a job we need to create a configuration object. configuration c = new configuration(); Job j = new Job(c,”wordcount calculation);

A= load ‘/home/training/simple.txt’ using PigStorage ‘|’ as (sname : chararray, sid: int, address:chararray);

local mode pig -x local pig -x mapreduce

dump command is used. grunt>dump A;

B = foreach A generate sname, sid;

Big Data is defined as a collection of large and complex of unstructured data sets from where insights are derived from the Data Analysis using open-source tools like Hadoop.

The five Vs of Big Data are – Volume – Amount of data in the Petabytes and Exabytes Variety – Includes formats like an videos, audio sources, textual data, etc. Velocity – Everyday data growth which are includes conversations in forums,blogs,social media posts,etc. Veracity – Degree of accuracy of data are available Value – Deriving insights from collected data to the achieve business milestones and new heights

Apache Hadoop is an open-source framework used for the storing, processing, and analyzing complex unstructured data sets for the deriving insights and actionable intelligence for businesses. The three main components of Hadoop are- MapReduce – A programming model which processes large datasets in the parallel HDFS – A Java-based distributed file system used for the data storage without prior organization YARN – A framework that manages resources and handles requests from the distributed applications

The Hadoop Distributed File System (HDFS) is the storage unit that’s responsible for the storing different types of the data blocks in the distributed environment. The two main components of HDFS are- NameNode – A master node that processes of metadata information for the data blocks contained in the HDFS DataNode – Nodes which act as slave nodes and a simply store the data, for use and then processing by the NameNode.

The Yet Another Resource Negotiator (YARN) is the processing component of the Apache Hadoop and is responsible for managing resources and providing an execution environment for said of processes. The two main components of YARN are- ResourceManager– Receives processing requests and allocates its parts to the respective Node Managers based on processing needs. Node Manager– Executes tasks on the every single Data Node

Commodity Hardware refers to hardware and components, collectively needed, to run the Apache Hadoop framework and related to the data management tools. Apache Hadoop requires 64-512 GB of the RAM to execute tasks, and any hardware that supports its minimum for the requirements is known as ‘Commodity Hardware.

Name Node – Port 50070 Task Tracker – Port 50060 Job Tracker – Port 50030

HDFS indexes data blocks based on the their respective sizes. The end of data block points to address of where the next chunk of data blocks get a stored. The DataNodes store the blocks of datawhile the NameNode manages these data blocks by using an in-memory image of all the files of said of data blocks. Clients receive for the information related to data blocked from the NameNode.

Edge nodes are gateway nodes in the Hadoop which act as the interface between the Hadoop cluster and external network.They run client applications and cluster administration tools in the Hadoop and are used as staging areas for the data transfers to the Hadoop cluster. Enterprise-class storage capabilities (like 900GB SAS Drives with Raid HDD Controllers) is required for the Edge Nodes,and asingle edge node for usually suffices for multiple of Hadoop clusters.

Oozie,Ambari,Hue,Pig and Flume are the most common of data management tools that work with edge nodes in the Hadoop. Other similar tools include to HCatalog,BigTop and Avro.

There are three core methods of a reducer. They are- setup() – Configures different to parameters like distributed cache, heap size, and input data. reduce() – A parameter that is called once per key with the concerned on reduce task cleanup() – Clears all temporary for files and called only at the end of on reducer task.

There are three main tombstone markers used for the deletion in HBase. They are- Family Delete Marker – Marks all the columns of an column family Version Delete Marker – Marks a single version of an single column Column Delete Marker– Marks all the versions of an single column

How to Approach: Unstructured data is the very common in big data. The unstructured data should be transformed into the structured data to ensure proper data are analysis.

Dual processors or core machines with an configuration of 4 / 8 GB RAM and ECC memory is ideal for running Hadoop operations. However, the hardware is configuration varies based on the project-specific workflow and process of the flow and need to the customization an accordingly.

Since Hadoop splits data into the various blocks, RecordReader is used to read the slit data into the single record. For instance, if our input data is the split like: Row1: Welcome to Row2: GangBoard It will be read as the “Welcome to GangBoard” using RecordReader.

Hadoop uses the specific file format which is known as the Sequence file. The sequence file stores data in the serialized key-value pair. Sequencefileinputformat is an input format to the read sequence files.

HDFS NameNode supports exclusive on write only. Hence, only the first user will receive to the grant for the file access & second that user will be rejected.

The following steps need to execute to the make the Hadoop cluster up and running: Use the FsImage which is file system for metadata replicate to start an new NameNode. Configure for the DataNodes and also the clients to make them acknowledge to the newly started NameNode. Once the new NameNode completes loading to the last for checkpoint FsImage which is the received to enough block reports are the DataNodes, it will start to serve the client. In case of large of Hadoop clusters, the NameNode recovery process to consumes a lot of time which turns out to be an more significant challenge in case of the routine maintenance.

It is an algorithm applied to the NameNode to decide then how blocks and its replicas are placed. Depending on the rack definitions network traffic is minimized between DataNodes within the same of rack. For example, if we consider to replication factor as 3, two copies will be placed on the one rack whereas the third copy in a separate rack.

The HDFS divides the input data physically into the blocks for processing which is known as the HDFS Block. Input Split is a logical division of data by the mapper for mapping operation.[/toggle_content]

Hadoop is not only for the storing large data but also to process those big data. Though DFS (Distributed File System) tool can be store the data, but it lacks below features- It is not fault for tolerant Data movement over the network depends on bandwidth.

Text Input Format – The default input format defined in the Hadoop is the Text Input Format. Sequence File Input Format – To read files in the sequence, Sequence File Input Format is used. Key Value Input Format – The input format used for the plain text files (files broken into lines) is the Key Value for Input Format.

Hadoop supports are the storage and processing of big data. It is the best solution for the handling big data challenges. Some of important features of Hadoop are 1. Open Source – Hadoop is an open source framework which means it is available free of cost Also,the users are allowed to the change the source code as per their requirements. 2. Distributed Processing – Hadoop supports distributed processing of the data i.e. faster processing. The data in Hadoop HDFS is stored in the distributed manner and MapReduce is responsible for the parallel processing of data. 3. Fault Tolerance – Hadoop is the highly fault-tolerant. It creates three replicas for each block at different nodes, by the default. This number can be changed in according to the requirement. So, we can recover the data from the another node if one node fails. The detection of node of failure and recovery of data is done automatically. 4. Reliability – Hadoop stores data on the cluster in an reliable manner that is independent of the machine. So, the data stored in Hadoop environment is not affected by the failure of machine. 5. Scalability – Another important feature of Hadoop is the scalability. It is compatible with the other hardware and we can easily as the new hardware to the nodes. 6. High Availability – The data stored in Hadoop is available to the access even after the hardware failure. In case of hardware failure, the data can be accessed from the another path.

Apache Hadoop runs are the following three modes – Standalone (Local) Mode – By default, Hadoop runs in the local mode i.e. on a non-distributed,single node. This mode use for the local file system to the perform input and output operation. This mode does not support the use of the HDFS, so it is used for debugging. No custom to configuration is needed for the configuration files in this mode. In the pseudo-distributed mode, Hadoop runs on a single of node just like the Standalone mode. In this mode, each daemon runs in the separate Java process. As all the daemons run on the single node, there is the same node for the both Master and Slave nodes. Fully – Distributed Mode – In the fully-distributed mode, all the daemons run on the separate individual nodes and thus the forms a multi-node cluster. There are different nodes for the Master and Slave nodes.

The jps command is used to the check if the Hadoop daemons are running properly or not. This command shows all the daemons running on the machine i.e. Datanode, Namenode, NodeManager, ResourceManager etc.

The main configuration parameters in “MapReduce” framework are: Input locations of Jobs in the distributed for file system Output location of Jobs in the distributed for file system The input format of data The output format of data The class which contains for the map function The class which contains for the reduce function JAR file which contains for the mapper, reducer and the driver classes

Blocks are smallest continuous of data storage in a hard drive. For HDFS, blocks are stored across Hadoop cluster. The default block size in the Hadoop 1 is: 64 MB The default block size in the Hadoop 2 is: 128 MB Yes,we can change block size by using the parameters – dfs.block.size located in the hdfs-site.xml file.

Distributed Cache is an feature of the Hadoop MapReduce framework to cache files for the applications. Hadoop framework makes cached files for available for every map/reduce tasks running on the data nodes. Hence, the data files can be access the cache file as the local file in the designated job.

The three running modes of the Hadoop are as follows: Standalone or local: This is the default mode and doesn’t need any configuration. In this mode, all the following components for Hadoop uses local file system and runs on single JVM – NameNode DataNode ResourceManager NodeManager Pseudo-distributed: In this mode, all the master and slave Hadoop services is deployed and executed on a single node. Fully distributed: In this mode, Hadoop master and slave services is deployed and executed on the separate nodes.

JobTracker is a JVM process in the Hadoop to submit and track MapReduce jobs. JobTracker performs for the following activities in Hadoop in a sequence – JobTracker receives jobs that an client application submits to the job tracker JobTracker notifies NameNode to determine data node JobTracker allocates TaskTracker nodes based on the available slots. It submits the work on the allocated TaskTracker Nodes, JobTracker monitors on the TaskTracker nodes.

The different configuration files in Hadoop are – core-site.xml – This configuration file of contains Hadoop core configuration settings, for example, I/O settings, very common for the MapReduce and HDFS. It uses hostname an port. mapred-site.xml – This configuration file specifies a framework name for MapReduce by the setting hdfs-site.xml – This configuration file contains of HDFS daemons configuration for settings. It also specifies default block for permission and replication checking on HDFS. yarn-site.xml – This configuration of file specifies configuration settings for the ResourceManager and NodeManager.

Following are the difference between Hadoop 2 and Hadoop 3 – Kerberos are used to the achieve security in Hadoop. There are 3 steps to access an service while using Kerberos, at a high level. Each step for involves a message exchange with an server. Authentication – The first step involves authentication of the client to authentication server, and then provides an time-stamped TGT (Ticket-Granting Ticket) to the client. Authorization – In this step, the client uses to received TGT to request a service ticket from the TGS (Ticket Granting Server) Service Request – It is the final step to the achieve security in Hadoop. Then the client uses to service ticket to authenticate an himself to the server.

Commodity hardware is an low-cost system identified by the less-availability and low-quality. The commodity hardware for comprises of RAM as it performs an number of services that require to RAM for the execution. One doesn’t require high-end hardware of configuration or super computers to run of Hadoop, it can be run on any of commodity hardware.

There are a number of the distributed file systems that work in their own way. NFS (Network File System) is one of the oldest and popular distributed file an storage systems whereas HDFS (Hadoop Distributed File System) is the recently used and popular one to the handle big data.

There are two phases of the MapReduce operation. Map phase – In this phase, the input data is split by the map tasks. The map tasks run in the parallel. These split data is used for analysis for purpose. Reduce phase – In this phase, the similar split data is the aggregated from the entire to collection and shows the result.[/toggle_content]

MapReduce is a programming model in the Hadoop for processing large data sets over an cluster of the computers, commonly known as the HDFS. It is a parallel to programming model. The syntax to run a MapReduce program is the hadoop_jar_file.jar /input_path /output_path.

Hadoop distributed file system (HDFS) uses an specific permissions model for files and directories. 1. Following user levels are used in HDFS – Owner Group Others. 2. For each of the user on mentioned above following permissions are applicable – read (r) write (w) execute(x). 3. Above mentioned permissions work on differently for files and directories. For files The r permission is for reading an file The w permission is for writing an file. For directories The r permission lists the contents of the specific directory. The w permission creates or deletes the directory. The X permission is for accessing the child directory.

The basic parameters of a Mapper is the LongWritable and Text and Int Writable

To restart all the daemons, it is required to the stop all the daemons first. The Hadoop directory contains sbin as directory that stores to the script files to stop and start daemons in the Hadoop. Use stop daemons command /sbin/ to the stop all the daemons and then use /sin/ command to start all the daemons again.

There are two methods to the overwrite the replication factors in HDFS – Method 1: On File Basis In this method, the replication factor is the changed on the basis of file using to Hadoop FS shell. The command used for this is: $hadoop fs – setrep –w2/my/test_file Here, test_file is the filename that’s replication to factor will be set to 2. Method 2: On Directory Basis In this method, the replication factor is changed on the directory basis i.e. the replication factor for all the files under the given directory is modified. $hadoop fs –setrep –w5/my/test_dir Here, test_dir is the name of the directory, then replication factor for the directory and all the files in it will be set to 5.

A NameNode without any for data doesn’t exist in Hadoop. If there is an NameNode, it will contain the some data in it or it won’t exist.[/toggle_content]

The NameNode recovery process involves to the below-mentioned steps to make for Hadoop cluster running: In the first step in the recovery process, file system metadata to replica (FsImage) starts a new NameNode. The next step is to configure DataNodes and Clients. These DataNodes and Clients will then acknowledge of new NameNode. During the final step, the new NameNode starts serving to the client on the completion of last checkpoint FsImage for loading and receiving block reports from the DataNodes. Note: Don’t forget to mention, this NameNode recovery to process consumes an lot of time on large Hadoop clusters. Thus, it makes routine maintenance to difficult. For this reason, HDFS high availability architecture is recommended to use.

CLASSPATH includes necessary directories that contain the jar files to start or stop Hadoop daemons. Hence, setting the CLASSPATH is essential to start or stop on Hadoop daemons. However, setting up CLASSPATH every time its not the standard that we follow. Usually CLASSPATH is the written inside /etc/hadoop/ file. Hence, once we run to Hadoop, it will load the CLASSPATH is automatically.

This is due to the performance issue of the NameNode.Usually, NameNode is allocated with the huge space to store metadata for the large-scale files. The metadata is supposed to be an from a single file for the optimum space utilization and cost benefit. In case of the small size files, NameNode does not utilize to the entire space which is a performance optimization for the issue.

Datasets in HDFS store as the blocks in DataNodes the Hadoop cluster. During the execution of the MapReducejob the individual Mapper processes to the blocks (Input Splits). If the data does not reside in the same node where the Mapper is the executing the job, the data needs to be copied from DataNode over the network to mapper DataNode. Now if an MapReduce job has more than 100 Mapper and each Mapper tries to copy the data from the other DataNode in cluster simultaneously, it would cause to serious network congestion which is an big performance issue of the overall for system. Hence, data proximity are the computation is an effective and cost-effective solution which is the technically termed as Data locality in the Hadoop. It helps to increase the overall throughput for the system. Enroll Now!

Only a concept that facilitates handling large data databases. Hadoop has a single framework for dozens of tools. Hadoop is primarily used for block processing. The difference between Hadoop, the largest data and open source software, is a unique and basic one.

Analysts are increasing demand for industry and large data buildings. Today, many people are looking to pursue their large data industry by having great data jobs like freshers. However, the larger data itself is just a huge field, so it’s just Hadoop jobs for freshers

The large data analytics has the highest value for any company, allowing it to make known decisions and give the edge among the competitors. A larger data career increases the opportunity to make a crucial decision for a career move.

Hadoop is not a type of database, but software software that allows software for computer software. It is an application of some types, which distributes noSQL databases (such as HBase), allowing thousands of servers to provide data in lower performance to the rankings

Data scientists have many technical skills such as Hadoto, NoSQL, Python, Spark, R, Java and more. … For some people, data scientist must have the ability to manage using Hoodab alongside a good skill to run statistics against data set.

On the other hand, data analytics analyzes structured or structured data. Although they have a similar sound, there are no goals. … Great data is a term of very large or complex data sets that are not enough for traditional data processing applications

A data inspector’s task role involves analyzing data collection and using various statistical techniques. … When a data inspector interviewed for the job role, the candidates must do everything they can to see their communication skills, analytical skills and problem solving skills

Big data refers to the very large and complex data sets for traditional data entry and data management applications. … Data sets continue to grow and applications are becoming more and more time-consuming, with large data and large dataprocessing cloud moving more

This assessment is provided by 85 Facebook data scientist salary report (s) employees or based on statistical methods. When a factor in bonus and extra compensation, a data scientist on Facebook expected an average of $ 143,000 in salary

HODOOP is not just enough to replace RDGMS, but it is not really what you want to do. … Although it has many advantages to the source data fields, Hadoopcannot (and usually does) replace a data warehouse. When associated with related databases. However, this creates a powerful and versatile solution.

MapReduce is widely used in I / O forms, a sequence file is a flat file containing binary key / value pairs. Graphical publications are stored locally in sequencer. It provides Reader, Writer and Seater classes. The three series file formats are: Non-stick key / value logs. Record key / value records are compressed – only ‘values’ are compressed here. Pressing keys / value records – ‘Volumes’ are collected separately and shortened by keys and values. The ‘volume’ size can be configured.

The task tracker’s primary function, resource management (managing work supervisors), resource availability and monitoring of the work cycle (monitoring of docs improvement and wrong tolerance). This is a process that runs on a separate terminal, not often in a data connection. The tracker communicates with the label to identify the location of the data. The best mission to run tasks at the given nodes is to find the tracker nodes. Track personal work trackers and submit the overall job back to the customer. MapReduce works loads from the slush terminal.

Since the Hadoop data separates various blocks, recordReader is used to read split data in a single version. For example, if our input data is broken: Row1: Welcome Row2: Intellipaat It uses “Welcome to Intellipaat” using RecordReader.

A range of Hadoop, some sloping nodes, are available to the program by distributing tasks at many ends. Tehre is a variety of causes because the tasks are slow, which are sometimes easier to detect. Instead of identifying and repairing slow-paced tasks, Hopep is trying to find out more slowly than he expected, then backs up the other equivalent task. Hadoop is the insulation of this backup machine spectrum. This creates a simulated task on another disk. You can activate the same input multiple times in parallel. After most work in a job, the rest of the functions that are free for the time available are the remaining jobs (slowly) copy copy of the splash execution system. When these tasks end, it is reported to JobTracker. If other copies are encouraging, Hudhoft dismays the tasktakers and dismiss the output. Hoodab is a normal natural process. To disable, set and mapred.reduce.tasks.speculative.execution Invalid job options

It will throw an exception that the output file directory already exists. To run MapReduce task, you need to make sure you do not have a pre-release directory in HDFS. To delete the directory before you can work, you can use the shell: Hadoop fs -rmr / path / to / your / output / or via Java API: FileSystem.getlocal (conf) .delete (outputDir, true);

First, check the list of currently running MapReduce jobs. Next, we need to see the orphanage running; If yes, then you have to determine the location of the RM records. Run: “ps -ef | grep -I ResourceManager” And search result log in result displayed. Check the job-id from the displayed list and check if there is any error message associated with the job. Based on RM records, identify the employee tip involved in executing the task. Now, log on to that end and run – “ps -ef | grep -iNodeManager” Check the tip manager registration. Major errors reduce work from user level posts for each diagram.

Hdfs-site.xml is used to configure HDFS. Changing the dfs.replication property on hdfs-site.xml will change the default response to all files in HDFS. You can change the reflection factor based on a file you are using Hadoop FS shell: [training @ localhost ~] $ hadoopfs -setrep -w 3 / n / fileConversely, You can also change the reflection factors of all the files under a single file. [Training @ localhotel ~] $ hadoopfs-setrep -w 3 -R / my / dir Now go through the Hadoop administrative practice to learn about the reflection factor in HDFS!

To achieve this summary, you must set: conf.set (“”, true) conf.set (“mapreduce.output.fileoutputformat.compress”, incorrect)

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Secondary mode should always be used on a separate separate computer. This prevents intermittent interaction with the mainstream.

There are various methods to run the Hadoop code – Fully distributed method Pseudosiphrit method Complete mode

Linux is the main operating system. However, it is also used as an electric power Windows operating system with some additional software.

HDFS is more efficient for a large number of data sets, maintained in a file Compared to smaller particles of data stored in multiple files. Saving NameNode The file system metadata in RAM, the amount of memory that defines the number of files in the HDFS file System. In simpler terms, more files will generate more metadata, which means more Memory (RAM). It is recommended that you take 150 bytes of a block, file or directory metadata.

There are three important properties of hdfssite.xml: data.dr – Identify the location of the data storage. name.dr – Specify the location of the metadata storage and specify the DFS is located On disk or remote location. checkpoint.dir – for the second name name.

Some of the essential hoopoe tools that enhance large data performance – Hive, HDFS, HBase, Avro, SQL, NoSQL, Oozie, Clouds, Flume, SolrSee / Lucene, and ZooKeeper

The sequence is defined as a flat file containing the binary key or value pairs. This is important Used in MapReduce’s input / output format. Graphical publications are stored locally SequenceFile. Several forms of sequence – Summary of record key / value records – In this format, the values are compressed. Block compressed key / value records – In this format, the values and keys are individually The blocks are stored and then shortened. Sticky Key / Value Entries – In this format, there are no values or keys.

In Hadoop, the work tracker’s performers perform various functions, such as – It manages resources, manages resources and manages life cycle Tasks. It is responsible for finding the location of the data by contacting the name Node. It performs tasks at the given nodes by finding the best worker tracker. Work Tracker Manages to monitor all task audits individually and then submit The overall job for the customer. It is responsible for supervising local servicemen from Macpute’s workplace Node.

The following points distinguish HDFS from NAS – Hadoop shared file system (HDFS) is a distributed file system that uses data Network Attached Storage (NAS) is a file-wide server Data storage is connected to the computer network. HDFS distributes all databases in a distributed manner As a cluster, NAS saves data on dedicated hardware. HDFS makes it invaluable when using NAS using materials hardware Data stored on highhend devices that include high spending The HDFS work with MapReduce diagram does not work with MapReduce Data and calculation are stored separately.

Yes, HDFS is very mistaken. Whenever some data is stored in HDFS, name it Copying data (copies) to multiple databases. Normal reflection factor is 3. It needs to be changed according to your needs. If DataNode goes down, NameNode will take Copies the data from copies and copies it to another node, thus making the data available automatically. TheThe way, as the HDFS is the wrong tolerance feature and the fault tolerance

The main difference between HDFS Block and Input Split is HDFS Black. While the precise section refers to the input sector, the business section of the data is knownData. For processing, HDFS first divides the data into blocks, and then stores all the packages Together, when MapReduce divides the data into the first input section then allocate this input and divide it Mapper function.

Remember that HDFS supports specific characters Only at a time). NName client nameNode is the nameNode that gives the name Node Lease the client to create this file. When the second client sends the request to open the same file To write, the lease for those files is already supplied to another customer, and the name of the name Reject second customer request.

The location for a hard drive or a hard drive to store data As the volume. Store data blocks in HDFS, and then distributed via the hoodo cluster. The entire file is divided into the first blocks and stored as separate units.

YARN still has another resource negotiation. This is a hoodup cluster Management system. It is also the next generation introduced by MapReduce and Hoodab 2 Account Management and Housing Management Resource Management. It helps to further support the hoodoop Different processing approaches and wide-ranging applications.

Node Manager is TARStracker’s YARN equivalent. It takes steps from it Manages resourceManager and single-source resources. This is the responsibility Containers and ResourceManager monitor and report their resource usage. Each Single container processes operated at slavery pad are initially provided, monitored and tracked By the tip manager associated with the slave terminal.

In Hadoop, RecordReader is used to read a single log split data. This is important Combining data, Hatopo divides data into various editions. For example, if input data is separated Row1: Welcome Line 2: The Hoodah’s World Using RecordReader, it should be read as “Welcome to the Hope World”.

In order to minimize the output of the maple, the output will not be affected and set as follows: Conf.set (“”, true) Conf.set (“mapreduce.output.fileoutputformat.compress”, incorrect)

Various methods of a Reducer include: System () – It is used to configure various parameters such as input data size. Syntax: general vacuum system (environment) Cleaning () – It is used to clean all temporary files at the end of the task. Syntax: General Vacuum Cleanup (Eco) Reduce () – This method is known in the heart of Rezar. This is used once A key to the underlying work involved. Syntax: reduce general void (key, value, environment)

For the configuration of HDFS, the hdfssite.xml file is used. Change the default value The reflection factor for all the files stored in HDFS is transferred to the following asset hdfssite.xml dfs.replication

The “Jps” command is used to verify that the Hadoop daemons state is running. TheList all hadoop domains running in the command line. Namenode, nodemanager, resource manager, data node etc

The output of the map is sorted and the partitions for the output will be created. The number of partitions depends on the number of disadvantages.

Any Reducer can control the keys (through which posts) by activating the custom partition.

It can be specified by Job.setCombinerClass (ClassName) to make local integration with a custom component or class, and intermediate outputs, which helps reduce the size of the transfers from the Mapper to Reducer.

The number of maps is usually driven by total inputs, that is, the total volume of input files. Usually it has a node for 10-100 maps. The work system takes some time, so it is best to take at least a minute to run maps. If you expect 10TB input data and have a 128MB volume, you will end up with 82,000 maps, which you can control the volume of the mapreduce.job.maps parameter (this only provides a note structure). In the end, the number of tasks are limited by the number of divisions returned by the InputFormat.getSplits () over time (you can overwrite).

Reducer reduces the set of intermediate values, which shares one key (usually smaller) values. The number of job cuts is set by Job.setNumReduceTasks (int).

The Reducer API is similar to a Mapper, a run () method, which modes the structure of the work and the reconfiguration of the reconfiguration framework from reuse. Run () method once (), minimize each key associated with the task to reduce (once), and finally clean up the system. Each of these methods can be accessed using the context structure of the task using Context.getConfiguration (). As for the mapper type, these methods may be violated with any or all custom processes. If none of these methods are violated, the default reduction action is a symbolic function; Values go further without processing. Reducer heart is its reduction (method). This is called a one-time one; The second argument is Iterable, which provides all the key related values.

Reducer is a sorted output of input mappers. At this point, the configuration receives a partition associated with the output of all the mappers via HTTP.

Structured groups at this point are Reducer entries with the keys (because different movers may have the same key output). Mixed and sequence phases occur simultaneously; They are combined when drawing graphic outputs (which are similar to the one-sequence).

At this point the reduction (MapOutKeyType, Iterable, environment) method is grouped into groups for each group. Reduction work output is typically written to FileSystem via Context.write (ReduceOutKeyType, ReduceOutValType). Applications can use application progress status, set up application level status messages, counters can update, or mark their existence. Reducer output is not sorted.