Top Answers to Apache Spark Interview Questions
1. Compare MapReduce with Spark.
|Processing speed||Good||Excellent (up to 100 times faster)|
|Data caching||Hard disk||In-memory|
|Performing iterative jobs||Average||Excellent|
|Dependency on Hadoop||Yes||No|
|Machine Learning applications||Average||Excellent|
2. What is Apache Spark?
Spark is a fast, easy-to-use, and flexible data processing framework. It has an advanced execution engine supporting a cyclic data flow and in-memory computing. Apache Spark can run standalone, on Hadoop, or in the cloud and is capable of accessing diverse data sources including HDFS, HBase, and Cassandra, among others.
Check out this insightful video on Spark Tutorial for Beginners:
3. Explain the key features of Spark.
- Apache Spark allows integrating with Hadoop.
- It has an interactive language shell, Scala (the language in which Spark is written).
- Spark consists of RDDs (Resilient Distributed Datasets), which can be cached across the computing nodes in a cluster.
- Apache Spark supports multiple analytic tools that are used for interactive query analysis, real-time analysis, and graph processing
Learn more key features of Apache Spark in this Apache Spark Tutorial!
4. Define RDD.
RDD is the acronym for Resilient Distribution Datasets—a fault-tolerant collection of operational elements that run in parallel. The partitioned data in an RDD is immutable and distributed. There are primarily two types of RDDs:
- Parallelized collections: The existing RDDs running in parallel with one another
- Hadoop datasets: Those performing a function on each file record in HDFS or any other storage system
5. What does a Spark Engine do?
A Spark engine is responsible for scheduling, distributing, and monitoring the data application across the cluster.
Read on Spark Engine and more in this Apache Spark Community!
6. Define Partitions.
As the name suggests, a partition is a smaller and logical division of data similar to a ‘split’ in MapReduce. Partitioning is the process of deriving logical units of data to speed up data processing. Everything in Spark is a partitioned RDD.
7. What operations does an RDD support?
8. What do you understand by Transformations in Spark?
Transformations are functions applied to RDDs, resulting in another RDD. It does not execute until an action occurs. Functions such as map() and filer() are examples of transformations, where the map() function iterates over every line in the RDD and splits into a new RDD. The filter() function creates a new RDD by selecting elements from the current RDD that passes the function argument.
9. Define Actions in Spark.
In Spark, an action helps in bringing back data from an RDD to the local machine. They are RDD operations giving non-RDD values. The reduce() function is an action that is implemented again and again until only one value if left. The take() action takes all the values from an RDD to the local node.
10. Define the functions of Spark Core.
Serving as the base engine, Spark Core performs various important functions like memory management, monitoring jobs, providing fault-tolerance, job scheduling, and interaction with storage systems.
11. What is RDD Lineage?
Spark does not support data replication in memory and thus, if any data is lost, it is rebuild using RDD lineage. RDD lineage is a process that reconstructs lost data partitions. The best thing about this is that RDDs always remember how to build from other datasets.
12. What is Spark Driver?
Spark driver is the program that runs on the master node of a machine and declares transformations and actions on data RDDs. In simple terms, a driver in Spark creates SparkContext, connected to a given Spark Master. It also delivers RDD graphs to Master, where the standalone Cluster Manager runs.
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13. What is Hive on Spark?
Hive contains significant support for Apache Spark, wherein Hive execution is configured to Spark:
hive> set spark.home=/location/to/sparkHome; hive> set hive.execution.engine=spark;
Hive supports Spark on YARN mode by default.
14. Name the commonly used Spark Ecosystems.
- Spark SQL (Shark) for developers
- Spark Streaming for processing live data streams
- GraphX for generating and computing graphs
- MLlib (Machine Learning Algorithms)
- SparkR to promote R programming in the Spark engine
15. Define Spark Streaming.
Spark supports stream processing—an extension to the Spark API allowing stream processing of live data streams. Data from different sources like Kafka, Flume, Kinesis is processed and then pushed to file systems, live dashboards, and databases. It is similar to batch processing in terms of the input data which is here divided into streams like batches in batch processing.
Learn in detail about the Top Four Apache Spark Use Cases including Spark Streaming!
16. What is GraphX?
Spark uses GraphX for graph processing to build and transform interactive graphs. The GraphX component enables programmers to reason about structured data at scale.
17. What does MLlib do?
MLlib is a scalable Machine Learning library provided by Spark. It aims at making Machine Learning easy and scalable with common learning algorithms and use cases like clustering, regression filtering, dimensional reduction, and the like.
18. What is Spark SQL?
Spark SQL, better known as Shark, is a novel module introduced in Spark to perform structured data processing. Through this module, Spark executes relational SQL queries on data. The core of this component supports an altogether different RDD called SchemaRDD, composed of row objects and schema objects defining the data type of each column in a row. It is similar to a table in relational databases.
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19. What is a Parquet file?
Parquet is a columnar format file supported by many other data processing systems. Spark SQL performs both read and write operations with the Parquet file and considers it be one of the best Big Data Analytics formats so far.
20. What file systems does Apache Spark support?
- Hadoop Distributed File System (HDFS)
- Local file system
- Amazon S3
21. What is YARN?
Similar to Hadoop, YARN is one of the key features in Spark, providing a central and resource management platform to deliver scalable operations across the cluster. Running Spark on YARN needs a binary distribution of Spark that is built on YARN support.
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22. List the functions of Spark SQL.
Spark SQL is capable of:
- Loading data from a variety of structured sources
- Querying data using SQL statements, both inside a Spark program and from external tools that connect to Spark SQL through standard database connectors (JDBC/ODBC), e.g., using Business Intelligence tools like Tableau
- Providing rich integration between SQL and the regular Python/Java/Scala code, including the ability to join RDDs and SQL tables, expose custom functions in SQL, and more.
23. What are the benefits of Spark over MapReduce?
- Due to the availability of in-memory processing, Spark implements data processing 10–100x faster than Hadoop MapReduce. MapReduce, on the other hand, makes use of persistence storage for any of the data processing tasks.
- Unlike Hadoop, Spark provides in-built libraries to perform multiple tasks using batch processing, steaming, Machine Learning, and interactive SQL queries. However, Hadoop only supports batch processing.
- Hadoop is highly disk-dependent, whereas Spark promotes caching and in-memory data storage.
- Spark is capable of performing computations multiple times on the same dataset, which is called iterative computation. Whereas, there is no iterative computing implemented by Hadoop.
For more insights, read on Spark vs MapReduce!
24. Is there any benefit of learning MapReduce?
Yes, MapReduce is a paradigm used by many Big Data tools, including Apache Spark. It becomes extremely relevant to use MapReduce when data grows bigger and bigger. Most tools like Pig and Hive convert their queries into MapReduce phases to optimize them better.
25. What is Spark Executor?
When SparkContext connects to Cluster Manager, it acquires an executor on the nodes in the cluster. Executors are Spark processes that run computations and store data on worker nodes. The final tasks by SparkContext are transferred to executors for their execution.
26. Name the types of Cluster Managers in Spark.
The Spark framework supports three major types of Cluster Managers.
- Standalone: A basic Cluster Manager to set up a cluster
- Apache Mesos: A generalized/commonly-used Cluster Manager, running Hadoop MapReduce and other applications
- YARN: A Cluster Manager responsible for resource management in Hadoop
27. What do you understand by a Worker node?
A worker node refers to any node that can run the application code in a cluster.
28. What is PageRank?
A unique feature and algorithm in GraphX, PageRank is the measure of each vertex in a graph. For instance, an edge from u to v represents an endorsement of v‘s importance w.r.t. u. In simple terms, if a user at Instagram is followed massively, he/she will be ranked high on that platform.
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29. Do you need to install Spark on all the nodes of the YARN cluster while running Spark on YARN?
No, because Spark runs on top of YARN.
30. Illustrate some demerits of using Spark.
Since Spark utilizes more storage space when compared to Hadoop and MapReduce, there might arise certain problems. Developers need to be careful while running their applications on Spark. To resolve the issue, they can think of distributing the workload over multiple clusters, instead of running everything on a single node.
31. How to create an RDD?
Spark provides two methods to create an RDD:
- By parallelizing a collection in the driver program. This makes use of SparkContext’s ‘parallelize’ method val
IntellipaatData = Array(2,4,6,8,10) val distIntellipaatData = sc.parallelize(IntellipaatData)
- By loading an external dataset from external storage like HDFS, the shared file system