Top 15 Hadoop Interview Questions with Answers ?

1. What is Hadoop framework?

Ans: Hadoop is an open source framework which is written in Java by Apache Software Foundation. a framework is used to write software application which Wants  to process  More amount of data (It could handle multi-terabytes of data). It works in-parallel on large clusters which could have 1000 of computers (Nodes) on the clusters. It also processes data very reliably and fault-tolerant manner. See The below image how does it look.

2. What concept the Hadoop framework works?

Ans: It works on Map Reduce, and it is devised by Google.

3. What is Map Reduce?

Ans: Map reduce is an algorithm or concept to process Huge amount of data in a Faster way. According to its name, you can divide it Map and Reduce. The fundamental Map-Reduce work as a rule part the info informational collection into autonomous pieces.

Map Task: will process these chunks in a completely parallel manner (One node can Process one or more chunks)

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4.  What is computed and Storage Nodes?

Ans:

Register Node: This is the PC or machine where you're real business Logic will be executed.

Capacity Node: This is the PC or machine where your record framework lives to Store the preparing information. In the greater part of the cases, the process hub and capacity hub would be a similar Machine.

5. How does master-slave architecture in the Hadoop? 

Ans: The Map-Reduce system comprises of a solitary ace Job Tracker and Multiple slaves, each bunch hub will have one TaskskTracker. The ace is in charge of planning the employment' segment errands on the Slaves, observing them and re-executing the fizzled assignments. The slaves execute the Tasks as coordinated by the ace.

6. How does a Hadoop application look like or their primary components?

Ans: Minimally a Hadoop application would have the accompanying segments.

Info area of information

Yield area of prepared information.

A guide task.

A diminished undertaking.

Employment design

The Hadoop work customer at that point presents the activity (container/executable and so forth.) and design To the Job Tracker which at that point accepts the accountability of conveying the Software/arrangement to the slaves, planning assignments and checking them, giving status and indicative data to the activity customer.

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7. Explain how the input and output data format of the Hadoop framework?

Ans: The MapReduce system works solely on sets, that is, the Framework sees the contribution to the activity as a lot of sets and creates a lot of sets as the yield of the activity, possibly of various kinds. See the stream referenced underneath

(Information) - > Map - > - > join/arranging - > - > decrease - > (yield)

8. What is the restriction to the key and value class? 


Ans: The key and esteem classes must be serialized by the structure. To make them serializable Hadoop gives a Writable interface. As you most likely are aware of the java itself that the key of the Map ought to be practically identical, henceforth the key needs to actualize one more Interface Writable Comparable.

9. Explain the Word Count implementation via the Hadoop framework?

Ans: We will include the words in all the info record stream as beneath

input

Expect there are two records each having a sentence

Hi World Hello World (In record 1)

Hi World Hello World (In record 2)

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11. What Mapper does? 

Ans: Maps are the individual errands that change Input records into the middle of the road records. The changed middle records shouldn't be of a similar kind as the info records. A given info pair may guide to zero or many Output sets.

12. What is the Input Split in map reduce software?

Ans: An Input Split is a consistent portrayal of a unit (A piece) of information work for a Map task; e.g., a filename and a byte run inside that record to process or a column set in a content File.

13. What is the Input Format? 

Ans: The Input Format is in charge of the list (order) the Input Splits, and creating a Record Reader which will transform those intelligent work units into real physical Input records.

14. Where do you determine the Mapper Implementation? 

Ans: Generally mapper execution is indicated in the Job itself.

15. How Mapper is instantiated in running employment? 

Ans: The Mapper itself is instantiated in the running occupation, and will be passed a Map Context object which it can use to arrange itself.

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