50+ Hadoop Interview Questions

50+ Hadoop Interview Questions

Hadoop Interview Questions

1) What is Hadoop? 

Hadoop is a conveyed processing stage. It is written in Java. It comprises of the highlights like Google File System and MapReduce.

2) What stage and Java adaptation are required to run Hadoop? 

Java 1.6.x or higher variants are useful for Hadoop, ideally from Sun. Linux and Windows are the upheld working framework for Hadoop, yet BSD, Mac OS/X, and Solaris are increasingly renowned for working.

3) What sort of Hardware is best for Hadoop? 

Hadoop can keep running on a double processor/double center machines with 4-8 GB RAM utilizing ECC memory. It relies upon the work process needs.

4) What are the most well-known info designs characterized in Hadoop? 

These are the most widely recognized info designs characterized in Hadoop:




TextInputFormat is an as a matter of course input configuration.

5) How would you order a major information? 

The enormous information can be sorted utilizing the accompanying highlights:




6) Explain the utilization of .mecia class? 

For the gliding of media objects starting with one side then onto the next, we utilize this class.

7) Give the utilization of the bootstrap board. 

We use boards in bootstrap from the boxing of DOM parts.

8) What is the motivation behind catch gatherings? 

Catch bunches are utilized for the situation of more than one catches in a similar line.

9) Name the different kinds of records upheld by Bootstrap. 

Requested rundown

Unordered rundown

Definition list

10) Which direction is utilized for the recovery of the status of daemons running the Hadoop group? 

The 'jps' direction is utilized for the recovery of the status of daemons running the Hadoop group.

11) What is InputSplit in Hadoop? Clarify. 

At the point when a Hadoop work runs, it parts input records into pieces and relegates each split to a mapper for preparing. It is known as the InputSplit.

12) What is TextInputFormat? 

In TextInputFormat, each line in the content document is a record. Esteem is the substance of the line while Key is the byte counterbalanced of the line. For example, Key: longWritable, Value: content

13) What is the SequenceFileInputFormat in Hadoop? 

In Hadoop, SequenceFileInputFormat is utilized to peruse documents in succession. It is a particular compacted parallel document position which passes information between the yield of one MapReduce employment to the contribution of some other MapReduce work.

14) what number InputSplits is made by a Hadoop Framework? 

Hadoop makes 5 parts as pursues:

One split for 64K documents

Two parts for 65MB documents, and

Two parts for 127MB documents

15) What is the utilization of RecordReader in Hadoop? 

InputSplit is doled out with a work yet doesn't have the foggiest idea how to get to it. The record holder class is absolutely in charge of stacking the information from its source and convert it into keys pair reasonable for perusing by the Mapper. The RecordReader's example can be characterized by the Input Format.

16) What is JobTracker in Hadoop? 

JobTracker is an administration inside Hadoop which runs MapReduce employments on the bunch.

17) What is WebDAV in Hadoop? 

WebDAV is a lot of augmentation to HTTP which is utilized to help altering and transferring documents. On most working framework WebDAV offers can be mounted as filesystems, so it is conceivable to get to HDFS as a standard filesystem by uncovering HDFS over WebDAV.

18) What is Sqoop in Hadoop? 

Sqoop is a device used to exchange information between the Relational Database Management System (RDBMS) and Hadoop HDFS. By utilizing Sqoop, you can exchange information from RDBMS like MySQL or Oracle into HDFS just as sending out information from HDFS record to RDBMS.

19) What are the functionalities of JobTracker? 

These are the fundamental errands of JobTracker:

To acknowledge occupations from the customer.

To speak with the NameNode to decide the area of the information.

To find TaskTracker Nodes with accessible openings.

To present the work to the picked TaskTracker hub and screens the advancement of each undertaking.

20) Define TaskTracker. 

TaskTracker is a hub in the bunch that acknowledges undertakings like MapReduce and Shuffle activities from a JobTracker.

21) What is Map/Reduce work in Hadoop? 

Guide/Reduce work is a programming worldview which is utilized to permit monstrous versatility over the a great many server.

MapReduce alludes to two extraordinary and unmistakable undertakings that Hadoop performs. In the initial step maps employments which takes the arrangement of information and changes over it into another arrangement of information and in the second step, Reduce work. It takes the yield from the guide as information and packs those information tuples into the littler arrangement of tuples.

22) What is "map" and what is "reducer" in Hadoop? 

Guide: In Hadoop, a guide is a stage in HDFS question understanding. A guide peruses information from an info area and yields a key-esteem pair as per the info type.

Reducer: In Hadoop, a reducer gathers the yield produced by the mapper, forms it, and makes its very own last yield.

23) What is rearranging in MapReduce? 

Rearranging is a procedure which is utilized to play out the arranging and exchange the guide yields to the reducer as info.

24) What is NameNode in Hadoop? 

NameNode is, where Hadoop stores all the record area data in HDFS (Hadoop Distributed File System). We can say that NameNode is the highlight of a HDFS document framework which is in charge of keeping the record of the considerable number of records in the record framework, and tracks the record information over the group or numerous machines.

25) What is heartbeat in HDFS? 

Heartbeat is a flag which is utilized between an information hub and name hub, and between undertaking tracker and occupation tracker. On the off chance that the name hub or occupation tracker doesn't react to the flag, at that point it is viewed as that there is some issue with information hub or errand tracker.

26) How is ordering done in HDFS? 

There is a one of a kind method for ordering in Hadoop. When the information is put away according to the square size, the HDFS will continue putting away the last piece of the information which determines the area of the following piece of the information.
27) What happens when an information hub comes up short?

On the off chance that an information hub falls flat the activity tracker and name hub will recognize the disappointment. From that point forward, all assignments are re-planned on the fizzled hub and afterward name hub will repeat the client information to another hub.

28) What is Hadoop Streaming? 

Hadoop gushing is an utility which enables you to make and run map/lessen work. It is a nonexclusive API that permits programs written in any dialects to be utilized as Hadoop mapper.

29) What is a combiner in Hadoop? 

A Combiner is a little diminish process which works just on information created by a Mapper. At the point when Mapper emanates the information, combiner gets it as information and sends the yield to a reducer.

30) What are the Hadoop's three setup documents? 

Following are the three setup documents in Hadoop:

center site.xml



31) What are the system prerequisites for utilizing Hadoop? 

Following are the system prerequisite for utilizing Hadoop:

Secret key less SSH association.

Secure Shell (SSH) for propelling server forms.

32) What do you know by capacity and register hub? 

Capacity hub: Storage Node is the machine or PC where your document framework dwells to store the handling information.

Process Node: Compute Node is a machine or PC where your real business rationale will be executed.

33) Is it important to realize Java to learn Hadoop? 

On the off chance that you have considerable experience with any programming language like C, C++, PHP, Python, Java, and so forth. It might be extremely useful, however on the off chance that you are nil in java, it is important to learn Java and furthermore get the fundamental information of SQL.

34) How to investigate Hadoop code? 

There are numerous approaches to investigate Hadoop codes yet the most well known techniques are:

By utilizing Counters.

By web interface given by the Hadoop system.

35) Is it conceivable to give numerous contributions to Hadoop? In the event that truly, clarify. 

Truly, It is conceivable. The information group class gives techniques to embed various catalogs as contribution to a Hadoop work.

36) What is the connection among occupation and assignment in Hadoop? 

In Hadoop, an occupation is separated into various little parts known as the errand.

37) What is the contrast between Input Split and HDFS Block? 

The Logical division of information is called Input Split and physical division of information is called HDFS Block.
38) What is the difference between RDBMS and Hadoop?
RDBMS Hadoop
RDBMS is a relational database management system. Hadoop is a node based flat structure.
RDBMS is used for OLTP processing. Hadoop is used for analytical and for big data processing.
In RDBMS, the database cluster uses the same data files stored in shared storage. In Hadoop, the storage data can be stored independently in each processing node.
In RDBMS, preprocessing of data is required before storing it. In Hadoop, you don't need to preprocess data before storing it.

39) What is the distinction among HDFS and NAS? 

HDFS information squares are dispersed crosswise over neighborhood drives of all machines in a group though, NAS information is put away on devoted equipment.

40) What is the distinction among Hadoop and other information preparing apparatuses? 

Hadoop encourages you to increment or abatement the quantity of mappers without stressing over the volume of information to be prepared.

41) What is conveyed store in Hadoop? 

Conveyed store is an office given by MapReduce Framework. It is given to store records (content, documents and so forth.) at the season of execution of the activity. The Framework duplicates the fundamental records to the slave hub before the execution of any assignment at that hub.