This course is intended to help Apache Hadoop and Mapreduce Career Aspirants to prepare for the interview. hadoop fs -D fs.local.block.size=sizeinKB -put local_name remote_location, ERROR tool.ImportTool: Error during import: No primary key could be found for table . The MapReduce reducer has three phases: Ans. If you are looking for any such services, feel free to check our service offerings or you can email us at [email protected] with more details. We have served some of the leading firms worldwide. This definitive list of top Hadoop Interview Questions will cover the concepts including Hadoop HDFS, MapReduce, Pig, Hive, HBase, Spark, Flume, and Sqoop. Ans. RDBMS cannot store and process a large amount of data. She spends most of her time researching on technology, and startups. In such cases, dynamic partitions are used. Ans. In Apache Hadoop, if nodes do not fix or diagnose the slow-running tasks, the master node can redundantly perform another instance of the same task on another node as a backup (the backup task is called a Speculative task). Because I have checked that even PUT command has the restriction that the source file should present in the local file (same like copyFromLocal command). –columns “first_name, last_name, created_date” Here I have compiled a list of all Hadoop scenario based interview questions and tried to answer all those Hadoop real time interview questions. The scenario-based interview questions below measure your time management. The MapReduce Partitioner manages the partitioning of the key of the intermediate mapper output. But, before starting, I would like to draw your attention to the Hadoop revolution in the market. About 57% of hiring managers list that as a must. Write-Ahead Log (WAL) is a file storage and it records all changes to data in. Writes are fast in Hadoop because no schema validation happens during HDFS write. As this is the default mode of Hive and so you can find the below property set in hive-site.xml. This is one of those scenarios questions that judge prioritization skills. You can also check Hortonworks technical sheet on this for more details. Mindmajix - The global online platform and corporate training company offers its services through the best This entry was posted in Sqoop Interview Questions and Answers and tagged Sqoop Interview Questions and Answers for Experienced on January 2, 2015 by Siva In this post we will provide some practical Sqoop Interview Questions and Answers for experienced hadoop developers. Copyright © 2020 Mindmajix Technologies Inc. All Rights Reserved, In This Interview Questions, You Will Learn. Real Time Hadoop Interview Questions From Different Readers 3 This entry was posted in Hadoop Interview Questions for experienced and freshers Java Interview Questions MapReduce Interview Questions Pig Interview Questions for experienced and freshers on July 17, 2015 by Siva This tool tries to subsequently even out the block data distribution across the cluster. Ans. However, you can quite easily end u saying the wrong thing and end up not getting the job as a result! Here you should ensure that the partition column is the last column of the non-partitioned table. If you have ever appeared for the Hadoop interview, you must have experienced many Hadoop scenario based interview questions. amzn_assoc_marketplace = "amazon"; Question4: Explain about the different schedulers available in Hadoop. Basically, to make candidates familiar with the nature of questions that are likely to be asked on the subject of Hive, These Hive scenario based interview questions and answers are formulated. Passive NameNode has similar data as active NameNode and replaces it when it fails. It performs local reduce function on mapper result before they are distributed further. This has been a guide to List of Informatica Scenario based Interview Questions and answers so that the candidate can crackdown these Interview Questions easily. Join our subscribers list to get the latest news, updates and special offers delivered directly in your inbox. Q16) How to commission (adding) the nodes in the Hadoop cluster? Steps involved in Hadoop job submission: Ans. Here is the blog on Apache Hive interview questions in Hadoop Interview Questions series. Scenario: Suppose I have installed Apache Hive on top of my Hadoop cluster using default metastore configuration. If your table doesn’t have the primary key column, you need to specify -m 1 option for importing the data, or you have to provide –split-by argument with some column name. It executes Hadoop jobs in Apache Spark, MapReduce, etc. It can easily store and process a large amount of data compared to RDBMS. You add the partition column manually and move the file into the partition table manually. Dynamic Partition: Here every row of the data available in the file is read and partition is getting done through a MapReduce job. Ans. Rest of the content is very good and helps revise the concepts. You can check Hadoop Terminology for more details. amzn_assoc_placement = "adunit0"; Yes, we can build “Spark” for any specific Hadoop version. HDFS Federation enhances the present HDFS architecture through a clear separation of namespace and storage by enabling a generic block storage layer. The WAL ensures all the changes to the data can be replayed when a RegionServer crashes or becomes unavailable. Big Data refers to a large amount of data that exceeds the processing capacity of conventional database systems and requires a special parallel processing mechanism. This is one of those scenarios questions that judge prioritization skills. –target-dir /user/root/user_data \ Q2) Explain Big data and its characteristics. Generally, the daemon is nothing but a process that runs in the background. It is designed to provide high table-update rates and a fault-tolerant way to store a large collection of sparse data sets. What is the difference between Static and Dynamic Partition”]Partition in Hive is an important concept and is one of the best Hive performance tuning techniques as well. By default, the HDFS block size is 128MB for Hadoop 2.x. Interested in Apache Hadoop as a building block of your tech career? The number of partitions is equal to the number of reducers. It stores various types of data as blocks in a distributed environment and follows master and slave topology. A serializable object which executes a simple and efficient serialization protocol, based on DataInput and DataOutput. Identity Mapper is a default Mapper class which automatically works when no Mapper is specified in the MapReduce driver class. [/vc_cta][/vc_column][/vc_row][vc_row][vc_column][vc_cta h2=”12. So in –copyToLocal command, the destination has to be the local file system. Thus, one must have the proper knowledge of the cluster based on the current scenario which depends on the following factor: The actual data size to be store is around 600TB. Scenario Based Interview Questions. TIP #1 – Scenario-based interview questions appear to be relatively easy to answer upon first inspection. Accesses data from HBase tables using APIs and MapReduce. Also, you can use left semi join here. Question3: How will you restart a NameNode? FROM a Q5) What is the difference between a regular file system and HDFS? Q30) What is the purpose of dfsadmin tool? –columns “first_name, last_name, created_date” While you’re on the job hunt, Hadoop developer interview questions will explore whether you have the technical chops with this open-source framework, especially if you’re going for a role such as data engineer or B.I. SerDe is a combination of Serializer and Deserializer. MapReduce framework is used to write applications for processing large data in parallel on large clusters of commodity hardware. Integrate Oozie with the Hadoop stack, which supports several types of Hadoop jobs such as Streaming MapReduce, Java MapReduce, Sqoop, Hive, and Pig. Writables are used for creating serialized data types in Hadoop. As you saw, put can do what copyFromLocal is doing but the reverse is not true. How Much Java Knowledge Is Required To Learn Hadoop? Partition: Partition comes into picture when you are using more than one reducer. Ans. The new NameNode will start serving the client once it has completed loading the last checkpoint FsImage and enough block reports from the DataNodes. Every interview is different and the scope of a job is different too. Now, configure DataNodes and clients, so that they can acknowledge the new NameNode, that is started. So it is similar to what you call Hive Query optimization. Q1. Q14) Compare HDFS (Hadoop Distributed File System) and NAS (Network Attached Storage)? Now coming to the difference between static and dynamic partition, the static partition is the default case of Hive. So you have finally found your dream job in Hadoop Admin but are wondering how to crack the Hadoop Admin Interview and what could be the probable Hadoop Admin Interview Questions. In Hadoop 2.x, we have both Active and passive NameNodes. It periodically creates the checkpoints of filesystem metadata by merging the edits log file with FsImage file. The reason for asking such Hadoop Interview Questions is to check your Hadoop skills. Ans. We collected these questions from the candidates who gave interviews. 9. Hope it clarified the difference between the static partition and dynamic partition in Hive. Checkpoint Node is the new implementation of secondary NameNode in Hadoop. Ans. Counters are useful for collecting statistics about MapReduce jobs for application-level or quality control. Ans. Ans. Without much complex Java implementations in MapReduce, programmers can perform the same implementations very easily using Pig Latin. Reads are fast in RDBMS because the schema of the data is already known. Hadoop, Data Science, Statistics & others. .hdfs dfsadmin -point topology is used for printing the topology. Start the DataNode and NodeManager on the added Node. Apache ZooKeeper is a centralized service used for managing various operations in a distributed environment. Thus, one must have the proper knowledge of the cluster based on the current scenario which depends on the following factor: The actual data size to be store is around 600TB. Scenario based questions are certainly common at this stage. The site has been started by a group of analytics professionals and so far we have a strong community of 10000+ professionals who are either working in the data field or looking to it. Yet Another Resource Negotiator (YARN) is one of the core components of Hadoop and is responsible for managing resources for the various applications operating in a Hadoop cluster, and also schedules tasks on different cluster nodes. I will list those in this Hadoop scenario based interview questions post. It offers extensive storage for any type of data and can handle endless parallel tasks. Hadoop provides a feature called SkipBadRecords class for skipping bad records while processing mapping inputs. Hadoop is Java-based programming framework which is open source and it facilitates the dispensation and availability of storage space for extremely large data sets in a scattered counting and computing environment. Check This Hadoop Tutorial to Understand the Problem Scope | John Preston, https://cwiki.apache.org/confluence/display/Hive/LanguageManual+SubQueries, Top Machine Learning Applications in Healthcare, Binomo Review – Reliable Trading Platform, 5 Epic Ways to Light Up this Lockdown Period with Phone-Internet-TV Combos, 5 Best Online Grammar Checker Tools [Compiled List]. Ans. Hadoop Interview Questions. ? It is a highly reliable, distributed, and configurable tool that is specially designed to transfer streaming data to HDFS. –password root \ You can also subscribe without commenting. These Hadoop interview questions specify how you implement your Hadoop knowledge and approach to solve given big data problem. This rule is called Replica Placement Policy. Pig offers various built-in operators for data operations like filters, joins, sorting, ordering, etc., while to perform these same functions in MapReduce is an enormous task. Ans. If I use ‘Put’ command to copy the file from non-local location to HDFS, then it showing the error like there is no such source file in the local file system. Ans. Ans. Image Credit: mapr.com. The Hadoop Developer Interview guide has more complex and difficult to answer scenario based questions than what is shown below. Big data recruiters and employers use these kind of interview questions to get an idea if you have the desired competencies and hadoop skills required for the open hadoop job position. Ans. specialist. Look at Sqoop tutorial before you move further. Also, I will love to know your experience and questions asked in your interview. If you delete an external table the file still remains on the HDFS server. HDFS High availability is introduced in Hadoop 2.0. Often questions are asked based on a scenario or problem that your interviewer faced in the past and will be interested to check out the way in which solve the problem. They are: Ans. We will be covering Hadoop scenario based interview questions, Hadoop interview questions for freshers as well as Hadoop interview questions and answers for experienced. We cannot perform Aggregation in mapping because it requires sorting of data, which occurs only at the Reducer side. The methods used for restarting the NameNodes are the following: These script files are stored in the sbin directory inside the Hadoop directory store. amzn_assoc_asins = "0544227751,0062390856,1449373321,1617290343,1449361323,1250094259,1119231388"; Hdfs Tutorial is a leading data website providing the online training and Free courses on Big Data, Hadoop, Spark, Data Visualization, Data Science, Data Engineering, and Machine Learning. Discuss one important decision you made in your last role and the impact that decision had. Partition decides which reducer is responsible for a particular key. You can check more about us here. Q34) List the various site-specific configuration files available in Hadoop? It provides multiple namespaces in the cluster to improve scalability and isolation. Hadoop Pig runs both atomic data types and complex data types. It uses MapReduce to effect its distribution, reporting, recovery,  and error handling. Troubleshooting and optimizations questions are really common in Hadoop … amzn_assoc_title = "My Amazon Picks"; It stores any kind of data. Use the below command to change the default block size in Hadoop. Consider the replication factor is 3 for data blocks on HDFS it means for every block of data two copies are stored on the same rack, while the third copy is stored on a different rack. 250+ Hadoop Administration Interview Questions and Answers, Question1: How will you decide whether you need to use the Capacity Scheduler or the Fair Scheduler? Schema of the data is known in RDBMS and it always depends on the structured data. –target-dir /user/root/user_data \ It is a compressed binary file format optimized for passing the data between outputs of one MapReduce job to the input of some other MapReduce job. These include HDFS, MapReduce, YARN, Sqoop, HBase, Pig and Hive. It performs all the administrative tasks on the HDFS. I am not sure when this article was written, but Hive supports IN and EXISTS at least since 2014. It means providing support for multiple NameNodes to the Hadoop architecture. Sqoop can import individual tables or entire databases into HDFS. The process of translating objects or data structures state into binary or textual form is called Avro Serialization. Although it does have some limits to it which can be checked here: https://cwiki.apache.org/confluence/display/Hive/LanguageManual+SubQueries. ... Hive organizes tables into partitions for grouping similar type of data together based on a column or partition key. –connect jdbc:mysql://localhost/dbname \ FROM a LEFT SEMI JOIN b on (a.key = b.key), The major difference between the internal and external tables are-. HDFS (Hadoop Distributed File System) is the primary data storage unit of Hadoop. Hadoop works better for large amounts of data. In DataNodes, RAID is not necessary as storage is achieved by replication between the Nodes. Check out the Big Data Hadoop Training course and get certified today. And so each time you’ll load a file, you need to specify the state value as shown below. The Various HDFS Commands are listed bellow. When to use external and internal tables in Hive?”]Use EXTERNAL tables when: Data will be available directly for all partition when you will put it through command and not manually. Selects high volume data streams in real-time. Ans. In this Hadoop Interview Questions and Answers blog, we are going to cover top 100 Hadoop Interview questions along with their detailed answers. RDD(Resilient Distributed Datasets) is a fundamental data structure of Spark. The Hadoop Developer Interview guide has more complex and difficult to answer scenario based questions than what is shown below. This course is intended to help Apache Hadoop and Mapreduce Career Aspirants to prepare for the interview. Ans. You can use these Hadoop interview questions to prepare for your next Hadoop Interview. Apache Hadoop and Mapreduce Interview Questions has a collection of 120+ questions with answers asked in the interview for freshers and experienced (Programming, Scenario-Based, Fundamentals, Performance Tuning based Question and Answer). We fulfill your skill based career aspirations and needs with wide range of Here are the steps you can do to create the dynamic partition table with data. It is a data processing engine which provides faster analytics than Hadoop MapReduce. IdentityMapper.class is used as a default value when JobConf.setMapperClass is not set. –password root \ Build a new class that extends Partitioner Class. ResourceManager then scheduling tasks and monitoring them. This mainly saves the time required to load the data into Hive tables. Q15) What are the limitations of Hadoop 1.0? This is an open ended question and the interviewer is trying to see the level of hands-on experience you have in solving production issues. 1. Hive may have internal or external tables this is a choice that affects how data is loaded, controlled, and managed. For each logically equivalent plan, assign a cost. It views the input data set as a set of pairs and processes the map tasks in a completely parallel manner. You want Hive to completely manage the lifecycle of the table and data, Create a non-partitioned table X and load the data, Now create a partitioned table Y and specify the partition column (say state). Ans. Built-in fault-tolerance and redundancy are available. Active NameNode works and runs in the cluster. Ans. In this case, we can apply the partition based on the state. It is a file-level computer data storage server connected to a computer network, provides network access to a heterogeneous group of clients. Hadoop Developer Interview Questions for Experienced. Apache Hive offers a database query interface to Apache Hadoop. Ans. As this is not the default mode of Hive and so you need to set the following two properties in Hive-site.XML file. –split-by created_date. Ans. amzn_assoc_ad_mode = "manual"; It maintains configuration data, performs synchronization, naming, and grouping. Surgnisirply well-written and informative for a free online article. Stored in a directory based on settings in hive.metastore.warehouse.dir, by default internal tables are stored in the following directory “/user/hive/warehouse” you can change it by updating the location in the config file. This can apply if you are pointing multiple schemas (tables or views) at a single data set or if you are iterating through various possible schemas. Q23)  How to keep an HDFS cluster balanced? 10 top interview questions asked in recent interviews. To crack an interview for Hadoop technology, you need to know the basics of Hadoop and the different frameworks used in big data to handle data. ... Hive organizes tables into partitions for grouping similar type of data together based on a column or partition key. Explain the different features of Hadoop. Apache Sqoop is a tool particularly used for transferring massive data between Apache Hadoop and external datastores such as relational database management, enterprise data warehouses, etc. Can we use LIKE operator in Hive?”]Yes, Hive supports LIKE operator, but it doesn’t support multi-value LIKE queries like below-. It receives inputs from the Map class and passes the output key-value pairs to the reducer class. (SELECT b.key Hadoop Interview Questions & Answers 2018. 44. Combiner: Combiner works like a mini reducer in Map phase which takes the input from map phase. The MapReduce framework represents the RecordReader instance through InputFormat. Ans. RecordReader in Hadoop uses the data from the InputSplit as input and converts it into Key-value pairs for Mapper. Ans. Hadoop Hive Interview Questions And Answers For Freshers, Experienced, hive scenario based interview questions, tricky hive interview questions BLACK FRIDAY OFFER: Flat 50% Off with Free Self Learning Course | Use Coupon BLACKFRIDAY50 COPY CODE Q2) Explain Big data and its characteristics. [/vc_cta][/vc_column][/vc_row], […] web scale information of several gigabytes or terabytes or petabytes. Often questions are asked based on a scenario or problem that your interviewer faced in the past and will be interested to check out the way in which solve the problem. It implements mapping inputs directly into the output. In this Big Data Hadoop Interview Questions blog, you will come across a compiled list of the most probable Big Data Hadoop questions that recruiters ask in the industry. Spot the difference in these answers: Here I have compiled a list of all Hadoop scenario based interview questions and tried to answer all those Hadoop real time interview questions. The interview panel asks the candidates who apply for hadoop developer or hadoop testing a few general questions as well as hadoop scenario based questions to check knowledge. Ans: IBM has a nice, simple explanation for the four critical features of big data: Volume –Scale of data Deleting the table deletes the metadata & data from master-node and HDFS respectively.