20 Best Hadoop Interview Questions & Answers

20 Best Hadoop Interview Questions & Answers

The Questions That You May Be Asked During a Hadoop Interview     

You must know that Hadoop experts are those who are having the most job opportunity nowadays. In order to be prepared for such an interview, you must be having a go through this article so that you are aware of the Hadoop Interview Questions. It is always better to be prepared for an interview rather than facing an awkward situation during the interview. Knowing the nature of questions that may be asked will make you confident about facing the interview and in the end, having the job. Continue reading and know the probable questions to make yourself suitable to be chosen for the offered job.

Let us see a number of the questions that you may face through such an interview. We have made sure to include the probable answers also so after understanding through this you feel that you are more equipped than the being who will be interviewing you.

What is Big Data and what are five V’s?

You may be thinking of what should be the answer to this question which has been asked. The answer should be that Big Data is that type of collection of data that is large and complex. Being such complex and large the processing of such kind of data is difficult using database management tools or other tools that are used for processing data. It is such that it is difficult to confine, curate, store up, look for, distribute, transmit, analyze, and to envisage. Big data has made opportunities for companies so that they can work efficiently with this nature of data.

Now let us see what you should say about the 5 V’s. The 5 V’s are:

  • Volume: It represents the quantity of data that is ever-expanding at an amazing rate in Petabytes and Exabytes.
  • Velocity: It is the fast rate at which these data increases. It is such a rate that if you think today then the data that you had yesterday is obsolete. It is also seen that social media is the biggest contributor to such data.
  • Variety: These data are in various formats or varieties. They may be in the format of videos, CSV or audios. It may be in any other kind of format also.
  • Veracity: It is the doubt that is related to this nature of data. This happens due to the inconsistency and the incompleteness of the data. You cannot believe in the data sometimes and that is what is all about veracity.
  • Value: It is useless to have such data unless we can have trust with it. That is what value is all about.

So, what do you feel now about the answer to this question? You must be confident that you will be able to answer it.

What is Hadoop and what are the components that make it up?

This may be the second question that may be asked to you when you sit for this nature of an interview. Let us prepare ourselves for this question so that as asked we can answer that and impress the interviewer.

It is seen that when Big Data started causing problems a solution was evolved through Apache Hadoop. It is software that gives us access to various natures of tools and services by means of which we can work with Big Data. Using these tools and services we can stock up and process Big Data. If we use the traditional system then we cannot efficiently analyze this nature of data and derive the results which are beneficial to us but using this innovative technology we can do that in the most efficient manner.

So, prepared with the answer and having the confidence to succeed.

What is the meaning of HDFS and YARN? 

This may be another one from the set of Hadoop Interview Questions that you may be asked. The full form of HDFS is Hadoop Distributed File System and this is the storage place of Hadoop. It is the unit that is responsible for the storage and maintenance of data. The data are saved as blocks in an environment that are distributed. The topology that is followed in this method is master and slave. There are two components of this nature of storage. They are:

  • Name node
  • Data node

Let us now know about YARN, the full form is Yet Another Resource Negotiator. This is where the entire processing is done and this helps to administer assets and provides an implementation setting to the processes. Over here also there are two components. They are:

  • Resource Manager
  • Node Manager

So, what are you feeling about yourself? Getting confident, isn’t it? Continue reading and you will be able to know about various other questions that you may be asked during the interview. It is certain that after finishing reading you will know more than your interviewer and will be certain to have the job.

What are the various Hadoop daemons and what are their roles?

You may be confused about how to answer this question. You are confused as you have to tell about a lot of things to give a proper answer. There is nothing to be confused about. Tell about the Hadoop demons like Name Node, Data Node, and Secondary Name Node and then tell about the YARN daemons which are Resource Manager and Node Manager and then if the interviewer does not ask the next question explain about Job History Server. Now let us know what exactly has to be told.

  • Name Node: It is the node that is a master in nature and is accountable for up keeping the metadata of all the documents that are in the data. It has the knowledge about blocks, that creates a file, and also about the location of those blocks in the cluster.
  • Data node: It is the node that is a slave in nature and it is that which retains the actual data.
  • Secondary Name Node: It at regular intervals assimilates the changes with the FsImage, currently in the Name Node. It stores the tailored FsImage into unrelenting storage space, and that can be used when there is a failure of the Name Node.
  • Resource Manager: It is the essential authority that tackles all the resources and calendar applications that are running on top of YARN.
  • Node Manager: It is the one that is responsible for the initiation of the application’s space, adjusting their resource usage and letting the Resource Manager know about it.
  • Job History Server: It keeps track of the information regarding Map Reduce jobs after the termination of Application Master.

Are you confused now also? You should not be, this is the answer that you should give to impress the interviewer. It may so happen that after you answer this question you may not be asked further but then also let us see some other questions so as to be prepared completely.

What is the comparison between HDFS and NAS?

Another bombshell, are you looking at this question in this manner. There is nothing to worry about just continuing reading and you will understand what you need to answer. First, you have to explain HDFS and NAS and then you can compare the features that they are made of.

  • NAS is a data storage server that is connected to a network of computers that enables the assorted group of clientele access to data. This can be hardware and also can be software. Now HDFS which is a file system distributed in nature and it stores the required data in commodity hardware.
  • Data stored in HDFS is distributed along all the computers that are in the network while in NAS the storage is made in hardware is specially dedicated for this purpose.
  • Both of them work using MapReduce Program but in HDFS computation is associated with the data and in NAS the data is kept separate from the computation.
  • HDFS is cost-effective as there is the usage of commodity hardware but NAS is costly comparatively as it uses a dedicated server for this purpose.

I think after reading this answer you can clearly explain to your interviewer why you should be the one who should be given the job and no one else.

What is the difference between active and passive Name Nodes?

Ahh! A simple question that has been asked. But then also let us know the answer so that we do not get confused or be overconfident at any stage. The answer to this question is:

If the architecture that we are using is of high end then there are two nodes namely, Active Name Node and the Passive Name Node.

If the Name Nodes works in the clusters then it is the Active one, whereas if it works in the standby mode then it is the Passive one. The utility of having two Nodes is that upon the failure of one the other can take over.

What is the most common task of a Hadoop administrator?

Do, you know the answer? You must be knowing the answer but for the benefit of others let us know the answer. The most common task of such an administrator is adding and removing the Data Nodes in a cluster. There are definitely reasons for this task. Surely, there are two reasons. As Hadoop uses commodity hardware there are frequent crashes which happen in such a cluster, this is one of the reasons for this nature of task for an administrator and the other reason is the ease with which it can be escalated along with the increase of data.

What is the role of jps command?

This may be the next question from the set of Hadoop Interview Questions that you are asked. The answer is quite simple. It gives you information regarding daemon status. It lets you know the status of all the Nodes along with those of Job and task tracker.

Mention the names of the modes in which Hadoop can be run?

This is also a simple question to answer but it is always advisable to be prepared with simple questions also. The three modes in which Hadoop can be run are:

  • Mode which is standalone in nature
  • Mode which is Pseudo distributed can also be a way of running Hadoop
  • Again you can have a fully distributed mode for running Hadoop

What are the input formats by means of which you can operate Hadoop?

It is always seen that those who are ready with minute answers wins at the interview table. You may be thinking that is this that nature of the question which can be asked in an interview. You never know, this may be the one which can lead your path to success. So, be prepared with this also. The answer to this one is that there are three input formats that can be used in Hadoop. They are:

  • Text Input
  • Key value Input and
  • Sequence File Input

Do you know the job role of Job Tracker? If yes then explain.

This may be the next one which you are asked. The answer is simple but it should be answered in sequence so that the role can be explained at the same time.

The job roles of Job Tracker are the following:

  • It accepts works from customers
  • As it accepts the job it establishes a communication with the Name node to determine where the data is located.
  • It then tries to find out which Task Tracker node has available slots
  • It then allocates the job to that particular Task Tracker Node and also determines the progress of the job as it is done.

Explain Heartbeat in Hadoop?

You may be thinking that the interviewer has gone mad. You may be thinking heartbeat and that too of Hadoop. Yes, that is true, it too has a heartbeat. Let us know what it is. Heartbeat is the nature of signal which is used between two nodes namely data and name and also between two trackers namely job and task. If it is seen that there is no response from a name or task node then it can be ascertained that there is some problem with them.

Explain Hadoop streaming?

You may know the answer as these are basics that you must know in order to have the job and that is the reason why these are asked at interviews. They want to make sure that you have the basic clear in your mind.

The answer to this basic question is that streaming is that which helps you to generate and work with map job. This is the nature of generic API which allows any programs written in any language to be utilized in the mapper that is in Hadoop.

Do you know the method to debug Hadoop code?

The answer to this question must be certainly yes. There are many methods by means of which you can debug a Hadoop code. There are some popular methods for doing so. The most popular methods are:

  • Counters to be used
  • By using the interface that is presented by Hadoop

The method is simple and can be easily done. So, you are ready with the answer and can completely be confident with the answers that you give.

Explain the difference between other tools that process data and Hadoop?

Hadoop has a unique feature that is not available in other tools that process data. Hadoop gives you the opportunity to increase or decrease the mapper number depending on the quantity of the data. This makes the tool to be the one that is used by many.

Explain distributed cache?

This is the facility that is provided by the Map-Reduce feature. It is that which makes available the files that are needed to work upon at the time when a job is executed.

What is the nature of the storage of data used by Hadoop?

The nature of storage that is used by Hadoop is HBase.

Explain the relationship that is between job and task?

You may be thinking they both are similar. No, they are not in Hadoop. A job in Hadoop is divided into parts which are called tasks.

There may be lots of questions that can be asked in such an interview. But these are the ones which are the ones which are generally asked.

Being prepared with such type of Hadoop Interview Questions you will have the necessary confidence and mindset up so that you are the one who will be selected for the job. Try to face the interviewer with the level of confidence so that they feel that you know all about Hadoop. While answering a single question give the answer in such a form that all is explained about that question.

So, take the next opportunity that you have to appear at such an interview and have success which is knocking at your door.

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