Spark By Examples | Learn Spark Tutorial with Examples

In this Apache Spark Tutorial, you will learn Spark with Scala code examples and every sample example explained here is available at Spark Examples Github Project for reference. All Spark examples provided in this Apache Spark Tutorials are basic, simple, easy to practice for beginners who are enthusiastic to learn Spark, and these sample examples were tested in our development environment.

Note: In case if you can’t find the spark sample code example you are looking for on this tutorial page, I would recommend using the Search option from the menu bar to find your tutorial.

Related: Examples explained in this Spark with Scala Tutorial are also explained with PySpark Tutorial (Spark with Python) Examples

What is Apache Spark?

Apache Spark is an Open source analytical processing engine for large scale powerful distributed data processing and machine learning applications. Spark is Originally developed at the University of California, Berkeley’s, and later donated to Apache Software Foundation. In February 2014, Spark became a Top-Level Apache Project and has been contributed by thousands of engineers and made Spark as one of the most active open-source projects in Apache.

Apache Spark Features

  • In-memory computation
  • Distributed processing using parallelize
  • Can be used with many cluster managers (Spark, Yarn, Mesos e.t.c)
  • Fault-tolerant
  • Immutable
  • Lazy evaluation
  • Cache & persistence
  • Inbuild-optimization when using DataFrames
  • Supports ANSI SQL

Apache Spark Advantages

  • Spark is a general-purpose, in-memory, fault-tolerant, distributed processing engine that allows you to process data efficiently in a distributed fashion.
  • Applications running on Spark are 100x faster than traditional systems.
  • You will get great benefits using Spark for data ingestion pipelines.
  • Using Spark we can process data from Hadoop HDFS, AWS S3, Databricks DBFS, Azure Blob Storage, and many file systems.
  • Spark also is used to process real-time data using Streaming and Kafka.
  • Using Spark Streaming you can also stream files from the file system and also stream from the socket.
  • Spark natively has machine learning and graph libraries.

Apache Spark Architecture

Apache Spark works in a master-slave architecture where the master is called “Driver” and slaves are called “Workers”. When you run a Spark application, Spark Driver creates a context that is an entry point to your application, and all operations (transformations and actions) are executed on worker nodes, and the resources are managed by Cluster Manager.

apache spark architecture
Source: https://spark.apache.org/

Cluster Manager Types

As of writing this Apache Spark Tutorial, Spark supports below cluster managers:

  • Standalone – a simple cluster manager included with Spark that makes it easy to set up a cluster.
  • Apache Mesos – Mesons is a Cluster manager that can also run Hadoop MapReduce and Spark applications.
  • Hadoop YARN – the resource manager in Hadoop 2. This is mostly used, cluster manager.
  • Kubernetes – an open-source system for automating deployment, scaling, and management of containerized applications.

local – which is not really a cluster manager but still I wanted to mention as we use “local” for master() in order to run Spark on your laptop/computer.

Spark Installation

In order to run Apache Spark examples mentioned in this tutorial, you need to have Spark and it’s needed tools to be installed on your computer. Since most developers use Windows for development, I will explain how to install Spark on windows.

Download Apache Spark by accessing Spark Download page and select the link from “Download Spark (point 3)”. If you wanted to use a different version of Spark & Hadoop, select the one you wanted from drop downs and the link on point 3 changes to the selected version and provides you with an updated link to download.

Apache Spark Installation

After download, untar the binary using 7zip and copy the underlying folder spark-3.0.0-bin-hadoop2.7 to c:\apps

Now set the following environment variables.


SPARK_HOME  = C:\apps\spark-3.0.0-bin-hadoop2.7
HADOOP_HOME = C:\apps\spark-3.0.0-bin-hadoop2.7
PATH=%PATH%;C:\apps\spark-3.0.0-bin-hadoop2.7\bin

Setup winutils.exe

Download wunutils.exe file from winutils, and copy it to %SPARK_HOME%\bin folder. Winutils are different for each Hadoop version hence download the right version from https://github.com/steveloughran/winutils

spark-shell

Spark binary comes with interactive spark-shell. In order to start a shell, go to your SPARK_HOME/bin directory and type “spark-shell2“. This command loads the Spark and displays what version of Spark you are using.

Apache spark shell
spark-shell

By default, spark-shell provides with spark (SparkSession) and sc (SparkContext) object’s to use. Let’s see some examples.

spark shell
spark-shell create RDD

Spark-shell also creates a Spark context web UI and by default, it can access from http://localhost:4041.

Spark-submit

The spark-submit command is a utility to run or submit a Spark or PySpark application program (or job) to the cluster by specifying options and configurations, the application you are submitting can be written in Scala, Java, or Python (PySpark) code. You can use this utility in order to do the following.

  1. Submitting Spark application on different cluster managers like Yarn, Kubernetes, Mesos, and Stand-alone.
  2. Submitting Spark application on client or cluster deployment modes

./bin/spark-submit \
  --master  \
  --deploy-mode  \
  --conf  \
  --driver-memory g \
  --executor-memory g \
  --executor-cores   \
  --jars  
  --class  \
   \
  [application-arguments]

Spark Web UI

Apache Spark provides a suite of Web UIs (Jobs, Stages, Tasks, Storage, Environment, Executors, and SQL) to monitor the status of your Spark application, resource consumption of Spark cluster, and Spark configurations. On Spark Web UI, you can see how the operations are executed.

Spark Web UI tutorial
Spark Web UI

Spark History Server

Spark History server, keep a log of all completed Spark application you submit by spark-submit, spark-shell. before you start, first you need to set the below config on spark-defaults.conf


spark.eventLog.enabled true
spark.history.fs.logDirectory file:///c:/logs/path

Now, start spark history server on Linux or mac by running.


$SPARK_HOME/sbin/start-history-server.sh

If you are running Spark on windows, you can start the history server by starting the below command.


$SPARK_HOME/bin/spark-class.cmd org.apache.spark.deploy.history.HistoryServer

By default History server listens at 18080 port and you can access it from browser using http://localhost:18080/

history server
Spark History Server

By clicking on each App ID, you will get the details of the application in Spark web UI.

The history server is very helpful when you are doing Spark performance tuning to improve spark jobs where you can cross-check the previous application run with the current run.

Spark Modules

  • Spark Core
  • Spark SQL
  • Spark Streaming
  • Spark MLlib
  • Spark GraphX
Modules and components
Spark Modules

Spark Core

In this section of the Apache Spark Tutorial, you will learn different concepts of the Spark Core library with examples in Scala code. Spark Core is the main base library of the Spark which provides the abstraction of how distributed task dispatching, scheduling, basic I/O functionalities and etc.

Before getting your hands dirty on Spark programming, have your Development Environment Setup to run Spark Examples using IntelliJ IDEA

SparkSession

SparkSession introduced in version 2.0, It is an entry point to underlying Spark functionality in order to programmatically use Spark RDD, DataFrame and Dataset. It’s object spark is default available in spark-shell.

Creating a SparkSession instance would be the first statement you would write to program with RDDDataFrame and Dataset. SparkSession will be created using SparkSession.builder() builder pattern.


val spark:SparkSession = SparkSession.builder()
      .master("local[1]")
      .appName("SparkByExamples.com")
      .getOrCreate()   

Spark Context

SparkContext is available since Spark 1.x (JavaSparkContext for Java) and is used to be an entry point to Spark and PySpark before introducing SparkSession in 2.0. Creating SparkContext was the first step to the program with RDD and to connect to Spark Cluster. It’s object sc by default available in spark-shell.

Since Spark 2.x version, When you create SparkSession, SparkContext object is by default create and it can be accessed using spark.sparkContext

Note that you can create just one SparkContext per JVM but can create many SparkSession objects.

Apache Spark RDD Tutorial

RDD (Resilient Distributed Dataset) is a fundamental data structure of Spark and it is the primary data abstraction in Apache Spark and the Spark Core. RDDs are fault-tolerant, immutable distributed collections of objects, which means once you create an RDD you cannot change it. Each dataset in RDD is divided into logical partitions, which can be computed on different nodes of the cluster. 

This Apache Spark RDD Tutorial will help you start understanding and using Apache Spark RDD (Resilient Distributed Dataset) with Scala code examples. All RDD examples provided in this tutorial were also tested in our development environment and are available at GitHub spark scala examples project for quick reference.

In this section of the Apache Spark tutorial, I will introduce the RDD and explains how to create them and use its transformation and action operations. Here is the full article on Spark RDD in case if you wanted to learn more of and get your fundamentals strong.

RDD creation

RDD’s are created primarily in two different ways, first parallelizing an existing collection and secondly referencing a dataset in an external storage system (HDFSHDFSS3 and many more). 

sparkContext.parallelize()

sparkContext.parallelize is used to parallelize an existing collection in your driver program. This is a basic method to create RDD.


//Create RDD from parallelize    
val dataSeq = Seq(("Java", 20000), ("Python", 100000), ("Scala", 3000))   
val rdd=spark.sparkContext.parallelize(dataSeq)

sparkContext.textFile()

Using textFile() method we can read a text (.txt) file from many sources like HDFS, S#, Azure, local e.t.c into RDD.


//Create RDD from external Data source
val rdd2 = spark.sparkContext.textFile("/path/textFile.txt")

RDD Operations

On Spark RDD, you can perform two kinds of operations.

RDD Transformations

Spark RDD Transformations are lazy operations meaning they don’t execute until you call an action on RDD. Since RDD’s are immutable, When you run a transformation(for example map()), instead of updating a current RDD, it returns a new RDD.

Some transformations on RDD’s are flatMap()map()reduceByKey()filter()sortByKey() and all these return a new RDD instead of updating the current.

RDD Actions

RDD Action operation returns the values from an RDD to a driver node. In other words, any RDD function that returns non RDD[T] is considered as an action. RDD operations trigger the computation and return RDD in a List to the driver program.

Some actions on RDD’s are count()collect()first()max()reduce()  and more.

RDD Examples

Spark DataFrame Tutorial with Basic Examples

DataFrame definition is very well explained by Databricks hence I do not want to define it again and confuse you. Below is the definition I took it from Databricks.

DataFrame is a distributed collection of data organized into named columns. It is conceptually equivalent to a table in a relational database or a data frame in R/Python, but with richer optimizations under the hood. DataFrames can be constructed from a wide array of sources such as structured data files, tables in Hive, external databases, or existing RDDs.

– Databricks

DataFrame creation

The simplest way to create a DataFrame is from a seq collection. DataFrame can also be created from an RDD and by reading files from several sources.

using createDataFrame()

By using createDataFrame() function of the SparkSession you can create a DataFrame.


val data = Seq(('James','','Smith','1991-04-01','M',3000),
  ('Michael','Rose','','2000-05-19','M',4000),
  ('Robert','','Williams','1978-09-05','M',4000),
  ('Maria','Anne','Jones','1967-12-01','F',4000),
  ('Jen','Mary','Brown','1980-02-17','F',-1)
)

val columns = Seq("firstname","middlename","lastname","dob","gender","salary")
df = spark.createDataFrame(data), schema = columns).toDF(columns:_*)

Since DataFrame’s are structure format which contains names and column, we can get the schema of the DataFrame using df.printSchema()

df.show() shows the 20 elements from the DataFrame.


+---------+----------+--------+----------+------+------+
|firstname|middlename|lastname|dob       |gender|salary|
+---------+----------+--------+----------+------+------+
|James    |          |Smith   |1991-04-01|M     |3000  |
|Michael  |Rose      |        |2000-05-19|M     |4000  |
|Robert   |          |Williams|1978-09-05|M     |4000  |
|Maria    |Anne      |Jones   |1967-12-01|F     |4000  |
|Jen      |Mary      |Brown   |1980-02-17|F     |-1    |
+---------+----------+--------+----------+------+------+

In this Apache Spark SQL DataFrame Tutorial, I have explained several mostly used operation/functions on DataFrame & DataSet with working scala examples. This is a work in progress section where you will see more articles and samples are coming.

Spark DataFrame Advanced concepts

Spark Array and Map operations

Spark Aggregate

Spark SQL Joins

Spark Performance

Other Helpful topics on DataFrame

Spark SQL Schema & StructType

Spark SQL Functions

Spark SQL provides several built-in functions, When possible try to leverage standard library as they are a little bit more compile-time safety, handles null and perform better when compared to UDF’s. If your application is critical on performance try to avoid using custom UDF at all costs as these are not guarantee on performance.

In this section, we will see several Spark SQL functions Tutorials with Scala examples.

Spark Data Source with Examples

Spark SQL supports operating on a variety of data sources through the DataFrame interface. This section of the tutorial describes reading and writing data using the Spark Data Sources with scala examples. Using Data source API we can load from or save data to RDMS databases, Avro, parquet, XML e.t.c.

Text

CSV

JSON

Parquet

Avro

XML

Apache Spark SQL Tutorial

Spark SQL is one of the most used Spark modules which is used for processing structured columnar data format. Once you have a DataFrame created, you can interact with the data by using SQL syntax. In other words, Spark SQL brings native RAW SQL queries on Spark meaning you can run traditional ANSI SQL’s on Spark Dataframe. In the later section of this Apache Spark tutorial, you will learn in details using SQL selectwheregroup byjoinunion e.t.c

In order to use SQL, first, we need to create a temporary table on DataFrame using createOrReplaceTempView() function. Once created, this table can be accessed throughout the SparkSession and it will be dropped along with your SparkContext termination.

On a table, SQL query will be executed using sql() method of the SparkSession and this method returns a new DataFrame.


df.createOrReplaceTempView("PERSON_DATA")
val df2 = spark.sql("SELECT * from PERSON_DATA")
df2.printSchema()
df2.show()

Let’s see another example using group by.


val groupDF = spark.sql("SELECT gender, count(*) from PERSON_DATA group by gender")
groupDF.show()

This yields the below output


+------+--------+
|gender|count(1)|
+------+--------+
|     F|       2|
|     M|       3|
+------+--------+

Similarly, you can run any traditional SQL queries on DataFrame’s using Spark SQL.

Spark HDFS & S3 Tutorial

Spark Streaming Tutorial & Examples

Spark Streaming is a scalable, high-throughput, fault-tolerant streaming processing system that supports both batch and streaming workloads. It is used to process real-time data from sources like file system folder, TCP socket, S3KafkaFlumeTwitter, and Amazon Kinesis to name a few. The processed data can be pushed to databases, Kafka, live dashboards e.t.c

streaming
source: https://spark.apache.org/

Spark with Kafka Tutorials

Spark – HBase Tutorials & Examples

In this section of the Spark Tutorial, you will learn several Apache HBase spark connectors and how to read an HBase table to a Spark DataFrame and write DataFrame to HBase table.

Spark – Hive Tutorials

In this section, you will learn what is Apache Hive and several examples of connecting to Hive, creating Hive tables, reading them into DataFrame

Spark GraphX and GraphFrames

PySpark GraphFrames are introduced in Spark 3.0 version to support Graphs on DataFrame’s. Prior to 3.0, Spark has GraphX library which ideally runs on RDD and loses all Data Frame capabilities.

Learn Spark from these Books

References: