Introduction to Apache Spark

Apache Spark
In-Memory Data Processing
September 2014 Meetup
Organized by Big Data Hyderabad Meetup Group.
http://www.meetup.com/Big-Data-Hyderabad/
Rahul Jain
@rahuldausa

Agenda
• Why Spark
• Introduction
• Basics
• Hands-on
– Installation
– Examples
2

Quick Questionnaire
How many people know/work on Scala ?
How many people know/work on Python ?
How many people know/heard/are using Spark ?

Why Spark ?
• Most of Machine Learning Algorithms are iterative because each iteration
can improve the results
• With Disk based approach each iteration’s output is written to disk making
it slow
Hadoop execution flow
Spark execution flow
http://www.wiziq.com/blog/hype-around-apache-spark/

About Apache Spark
• Initially started at UC Berkeley in 2009
• Fast and general purpose cluster computing system
• 10x (on disk) - 100x (In-Memory) faster
• Most popular for running Iterative Machine Learning Algorithms.
• Provides high level APIs in
• Java
• Scala
• Python
• Integration with Hadoop and its eco-system and can read existing data.
• http://spark.apache.org/

Spark Stack
• Spark SQL
– For SQL and unstructured data
processing
• MLib
– Machine Learning Algorithms
• GraphX
– Graph Processing
• Spark Streaming
– stream processing of live data
streams
http://spark.apache.org

Execution Flow
http://spark.apache.org/docs/latest/cluster-overview.html

Terminology
• Application Jar
– User Program and its dependencies except Hadoop & Spark Jars bundled into a
Jar file
• Driver Program
– The process to start the execution (main() function)
• Cluster Manager
– An external service to manage resources on the cluster (standalone manager,
YARN, Apache Mesos)
• Deploy Mode
– cluster : Driver inside the cluster
– client : Driver outside of Cluster

Terminology (contd.)
• Worker Node : Node that run the application program in cluster
• Executor
– Process launched on a worker node, that runs the Tasks
– Keep data in memory or disk storage
• Task : A unit of work that will be sent to executor
• Job
– Consists multiple tasks
– Created based on a Action
• Stage : Each Job is divided into smaller set of tasks called Stages that is sequential
and depend on each other
• SparkContext :
– represents the connection to a Spark cluster, and can be used to create RDDs,
accumulators and broadcast variables on that cluster.

Resilient Distributed Dataset (RDD)
• Resilient Distributed Dataset (RDD) is a basic Abstraction in Spark
• Immutable, Partitioned collection of elements that can be operated in parallel
• Basic Operations
– map
– filter
– persist
• Multiple Implementation
– PairRDDFunctions : RDD of Key-Value Pairs, groupByKey, Join
– DoubleRDDFunctions : Operation related to double values
– SequenceFileRDDFunctions : Operation related to SequenceFiles
• RDD main characteristics:
– A list of partitions
– A function for computing each split
– A list of dependencies on other RDDs
– Optionally, a Partitioner for key-value RDDs (e.g. to say that the RDD is hash-partitioned)
– Optionally, a list of preferred locations to compute each split on (e.g. block locations for an HDFS file)
• Custom RDD can be also implemented (by overriding functions)

Cluster Deployment
• Standalone Deploy Mode
– simplest way to deploy Spark on a private cluster
• Amazon EC2
– EC2 scripts are available
– Very quick launching a new cluster
• Apache Mesos
• Hadoop YARN

Spark Shell
./bin/spark-shell --master local[2]
The --master option specifies the master URL for a distributed cluster, or local to run
locally with one thread, or local[N] to run locally with N threads. You should start by
using local for testing.
./bin/run-example SparkPi 10
This will run 10 iterations to calculate the value of Pi

Basic operations…
scala> val textFile = sc.textFile("README.md")
textFile: spark.RDD[String] = spark.MappedRDD@2ee9b6e3
scala> textFile.count() // Number of items in this RDD
ees0: Long = 126
scala> textFile.first() // First item in this RDD
res1: String = # Apache Spark
scala> val linesWithSpark = textFile.filter(line =>
line.contains("Spark"))
linesWithSpark: spark.RDD[String] = spark.FilteredRDD@7dd4af09
Simplier - Single liner:
scala> textFile.filter(line => line.contains("Spark")).count()
// How many lines contain "Spark"?
res3: Long = 15

Map - Reduce
scala> textFile.map(line => line.split(" ").size).reduce((a, b)
=> if (a > b) a else b)
res4: Long = 15
scala> import java.lang.Math
scala> textFile.map(line => line.split(" ").size).reduce((a, b)
=> Math.max(a, b))
res5: Int = 15
scala> val wordCounts = textFile.flatMap(line => line.split("
")).map(word => (word, 1)).reduceByKey((a, b) => a + b)
wordCounts: spark.RDD[(String, Int)] =
spark.ShuffledAggregatedRDD@71f027b8
wordCounts.collect()

With Caching…
scala> linesWithSpark.cache()
res7: spark.RDD[String] = spark.FilteredRDD@17e51082
scala> linesWithSpark.count()
res8: Long = 15
scala> linesWithSpark.count()
res9: Long = 15

With HDFS…
val lines = spark.textFile(“hdfs://...”)
val errors = lines.filter(line => line.startsWith(“ERROR”))
println(Total errors: + errors.count())

Standalone (Scala)
/* SimpleApp.scala */
import org.apache.spark.SparkContext
import org.apache.spark.SparkContext._
import org.apache.spark.SparkConf
object SimpleApp {
def main(args: Array[String]) {
val logFile = "YOUR_SPARK_HOME/README.md" // Should be some file on your
system
val conf = new SparkConf().setAppName("Simple Application")
.setMaster(“local")
val sc = new SparkContext(conf)
val logData = sc.textFile(logFile, 2).cache()
val numAs = logData.filter(line => line.contains("a")).count()
val numBs = logData.filter(line => line.contains("b")).count()
println("Lines with a: %s, Lines with b: %s".format(numAs, numBs))
}
}

Standalone (Java)
/* SimpleApp.java */
import org.apache.spark.api.java.*;
import org.apache.spark.SparkConf;
import org.apache.spark.api.java.function.Function;
public class SimpleApp {
public static void main(String[] args) {
String logFile = "YOUR_SPARK_HOME/README.md"; // Should be some file on your system
SparkConf conf = new SparkConf().setAppName("Simple Application").setMaster("local");
JavaSparkContext sc = new JavaSparkContext(conf);
JavaRDD<String> logData = sc.textFile(logFile).cache();
long numAs = logData.filter(new Function<String, Boolean>() {
public Boolean call(String s) { return s.contains("a"); }
}).count();
long numBs = logData.filter(new Function<String, Boolean>() {
public Boolean call(String s) { return s.contains("b"); }
}).count();
System.out.println("Lines with a: " + numAs + ", lines with b: " + numBs);
}
}

Standalone (Python)
"""SimpleApp.py"""
from pyspark import SparkContext
logFile = "YOUR_SPARK_HOME/README.md" # Should be some file on your
system
sc = SparkContext("local", "Simple App")
logData = sc.textFile(logFile).cache()
numAs = logData.filter(lambda s: 'a' in s).count()
numBs = logData.filter(lambda s: 'b' in s).count()
print "Lines with a: %i, lines with b: %i" % (numAs, numBs)

Job Submission
$SPARK_HOME/bin/spark-submit
--class "SimpleApp"
--master local[4]
target/scala-2.10/simple-project_2.10-1.0.jar

Configuration
val conf = new SparkConf()
.setMaster("local")
.setAppName("CountingSheep")
.set("spark.executor.memory", "1g")
val sc = new SparkContext(conf)

Thanks!
@rahuldausa on twitter and slideshare
http://www.linkedin.com/in/rahuldausa
27
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Introduction to Apache Spark

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