1. Intro to Apache Spark:
Fast cluster computing engine for
Hadoop
Intro to Scala:
Object-oriented and functional
language for the Java Virtual
Machine
ACM SIGKDD, 7/9/2014
Roger Huang
Lead System Architect
rohuang@visa.com
rog4096@yahoo.com
@BigDataWrangler
2. 2Intro to Spark: Intro to Scala | 7/9/2014
About me: Roger Huang
• Visa
– Digital & Mobile Products Architecture, Strategic Projects &
infrastructure
– Search infrastructure
– Customer segmentation
– Logging Framework
– Splunk on Hadoop (Hunk)
– Real-time monitoring
– Data
• PayPal
– Java Infrastructure
3. 3Intro to Spark: Intro to Scala | 7/9/2014
Different perspectives on an elephant Scala
4. 4Intro to Spark: Intro to Scala | 7/9/2014
Outline
• Spark
– Hadoop eco system
• Scala
– Background
• Why Scala?
– For the computer scientist
– For the Java / OO programmer
– For the Spark developer
– For the Big Data developer
– For the Big Data scientist / mathematician
– For the system architect
5. 5Intro to Spark: Intro to Scala | 7/9/2014
Spark in the Hadoop ecosystem
7. 7Intro to Spark: Intro to Scala | 7/9/2014
Resilient Distributed Dataset
• Fault tolerant collection of elements partitioned across the
nodes of the cluster that can be operated on in parallel
• Data sources for RDDs
– Parallelized collections
• From Scala collections
– Hadoop datasets
• From HDFS, any Hadoop supported storage system (Hbase, Amazon
S3, …)
• Text files, SequenceFile, any Hadoop InputFormat
• Two types of operations
– Transformation
• takes an existing dataset and creates a new one
– Action
• takes a dataset, run a computation, and return value to driver program
9. 9Intro to Spark: Intro to Scala | 7/9/2014
Scala background
• Scalable, Object oriented, functional language
– Version 2.11 (4/2014)
• Runs on the Java Virtual Machine
• Martin Odersky
– javac
– Java generics
• http://scala-lang.org/, REPL
• http://www.scala-lang.org/api/current
• http://scala-ide.org/
• http://www.scala-sbt.org/, Simple build tool
• Who’s using Scala?
– Twitter, LinkedIn, …
• Powered by Scala
– Apache Spark, Apache Kafka, Akka,…
10. 10Intro to Spark: Intro to Scala | 7/9/2014
Outline
• Spark
– Hadoop eco system
• Scala
– Background
• Why Scala?
– For the computer scientist
– For the Java / OO programmer
– For the Hadoop/Spark developer
– For the Big Data developer
– For the Big Data scientist / mathematician
– For the system architect
11. 11Intro to Spark: Intro to Scala | 7/9/2014
Scala for the computer scientist:
functional programming (FP)
12. 12Intro to Spark: Intro to Scala | 7/9/2014
Scala for the computer scientist:
functional programming (FP)
• Math functions, e.g., f(x) = y
– A function has a single responsibility
– A function has no side effects
– A function is referentially transparent
• A function outputs the same value for the same inputs.
• Functional programming
– expresses computation as the evaluation and composition of
mathematical functions
– Avoid side effects and mutating state data
13. 13Intro to Spark: Intro to Scala | 7/9/2014
Why functional programming?
• Multi core processors
• Concurrency
– Computation as a series of independent data transformations
– Parallel data transformations without side effects
• Referential transparency
14. 14Intro to Spark: Intro to Scala | 7/9/2014
Scala for the computer scientist:
functional programming
• Functions
– Lambda, closure
• For-comprehensions
• Type inference
• Pattern matching
• Higher order functions
– map, flatMap, foldLeft
• And more …
15. 15Intro to Spark: Intro to Scala | 7/9/2014
FP: functions
• Anonymous function
– Function without a name
– lambda function
• Example
– scala> List(100, 200, 300) map { _ * 10/100}
– res0: List[Int] = List(10, 20, 30)
• Closure (Wikipedia)
– Closure = A function, together with a referencing environment – a
table storing a reference to each of the non-local variables of that
function.
– A closure allows a function to access those non-local variables
even when invoked outside its immediate lexical scope.
16. 16Intro to Spark: Intro to Scala | 7/9/2014
FP: functions
• applyPercentage is an example of a closure
– scala> var percentage = 10
– percentage: Int = 10
– scala> val applyPercentage = (amount: Int) => amount *
percentage / 100
– applyPercentage: Int => Int = <function1>
– scala> percentage = 20
– percentage: Int = 20
– scala> List (100, 200, 300) map applyPercentage
– res1: List[Int] = List(20, 40, 60)
– scala>
17. 17Intro to Spark: Intro to Scala | 7/9/2014
FP: functions
• Anonymous function
• Closure
18. 18Intro to Spark: Intro to Scala | 7/9/2014
FP: Higher order functions
scala> :load Person.scala
Loading Person.scala...
defined class Person
scala> val jd = new Person("John", "Doe", 17)
jd: Person = Person@372a6e85
scala> val rh = new Person("Roger", "Huang", 34)
rh: Person = Person@611c4041
scala> val people = Array(jd, rh)
people: Array[Person] = Array(Person@372a6e85, Person@611c4041)
scala> val (minors, adults) = people partition (_.age < 18)
minors: Array[Person] = Array(Person@372a6e85)
adults: Array[Person] = Array(Person@611c4041)
scala>
19. 19Intro to Spark: Intro to Scala | 7/9/2014
FP: Higher order functions
• HOF
– takes a function as an argument
– Returns a function
20. 20Intro to Spark: Intro to Scala | 7/9/2014
FP: Higher order functions: map
• Creates a new collection from an existing collection by applying
a function
• Anonymous function
scala> List(1, 2, 3 ) map { (x: Int) => x + 1 }
res0: List[Int] = List(2, 3, 4)
• Function literal
scala> List(1, 2, 3) map { _ + 1 }
res1: List[Int] = List(2, 3, 4)
• Passing an existing function
scala> def addOne(num: Int) = num + 1
addOne: (num: Int)Int
scala> List(1, 2, 3) map addOne
res2: List[Int] = List(2, 3, 4)
21. 21Intro to Spark: Intro to Scala | 7/9/2014
FP: Higher order functions: map
22. 22Intro to Spark: Intro to Scala | 7/9/2014
FP: Higher order functions: flatmap
23. 23Intro to Spark: Intro to Scala | 7/9/2014
FP: for-comprehension
• Syntax
– for ( <generator> | <guard> ) <expression> [yield] <expression>
• Types
– Imperative form. Does not return a value.
scala> val aList = List(1, 2, 3)
aList: List[Int] = List(1, 2, 3)
scala> val bList = List(4, 5, 6)
bList: List[Int] = List(4, 5, 6)
scala> for { a <- aList; if (a < 2); b <- bList; if (b < 7) } println( a + b )
5
6
7
24. 24Intro to Spark: Intro to Scala | 7/9/2014
FP: for-comprehension
• Syntax
– for ( <generator> | <guard> ) <expression> [yield] <expression>
• Types
– Functional form (a.k.a., sequence comprehension) . Returns/yields
a value
scala> for { a <- aList; b <- bList} yield a + b
res0: List[Int] = List(5, 6, 7, 6, 7, 8, 7, 8, 9)
scala> res0.take(1)
res1: List[Int] = List(5)
scala> for { a <- aList; if (a < 2); b <- bList } yield a + b
res2: List[Int] = List(5, 6, 7)
scala>
28. 28Intro to Spark: Intro to Scala | 7/9/2014
FP: find the last item in an array
• scala> val ns = Array(20, 40, 60)
• ns: Array[Int] = Array(20, 40, 60)
• scala> ns.foldLeft(ns.head) {(acc, b) => b}
• res0: Int = 60
• scala>
29. 29Intro to Spark: Intro to Scala | 7/9/2014
FP: reverse an array w/ foldLeft
• scala> val ns = Array(20, 40, 60)
• ns: Array[Int] = Array(20, 40, 60)
• scala> ns.foldLeft( Array[Int]() ) { (acc, b) => b +: acc}
• res1: Array[Int] = Array(60, 40, 20)
• scala>
30. 30Intro to Spark: Intro to Scala | 7/9/2014
FP: reverse an array w/ foldLeft
31. 31Intro to Spark: Intro to Scala | 7/9/2014
Outline
• Spark
– Hadoop eco system
• Scala
– Background
• Why Scala?
– For the computer scientist
– For the Java / OO programmer
– For the Spark developer
– For the Big Data developer
– For the Big Data scientist / mathematician
– For the system architect
32. 32Intro to Spark: Intro to Scala | 7/9/2014
Scala for the Java / OO developer:
• Interoperable w/ Java
• Case classes
• Mixins with traits
33. 33Intro to Spark: Intro to Scala | 7/9/2014
Scala for the Java / OO developer:
• case class
– Implements equals(), hashCode(), toString()
– Can be used in Pattern Matching
34. 34Intro to Spark: Intro to Scala | 7/9/2014
Scala for the Java / OO developer:
• http://docs.oracle.com/javase/8/docs/api/java/util/stream/Str
eam.html
• map
– <R> Stream<R> map(Function<? super T,? extends
R> mapper)Returns a stream consisting of the results of applying
the given function to the elements of this stream.This is
an intermediate operation.
• flatMap
– <R> Stream<R> flatMap(Function<? super T,? extends Stream<?
extends R>> mapper)Returns a stream consisting of the results of
replacing each element of this stream with the contents of a
mapped stream produced by applying the provided mapping
function to each element. Each mapped stream is closed after its
contents have been placed into this stream. (If a mapped stream
is null an empty stream is used, instead.)This is an intermediate
operation.
`
35. 35Intro to Spark: Intro to Scala | 7/9/2014
Outline
• Spark
– Hadoop eco system
• Scala
– Background
• Why Scala?
– For the computer scientist
– For the Java / OO programmer
– For the Spark developer
– For the Big Data developer
– For the Big Data scientist / mathematician
– For the system architect
36. 36Intro to Spark: Intro to Scala | 7/9/2014
Scala for the Spark developer
• ResilientDistributedDataset (RDD)
• A Resilient Distributed Dataset (RDD), the basic abstraction in
Spark. Represents an immutable, partitioned collection of
elements that can be operated on in parallel. This class contains
the basic operations available on all RDDs, such as map, filter,
and persist.
• http://spark.apache.org/docs/latest/api/scala/index.html#org.apa
che.spark.rdd.RDD
37. 37Intro to Spark: Intro to Scala | 7/9/2014
Outline
• Spark
– Hadoop eco system
• Scala
– Background
• Why Scala?
– For the computer scientist
– For the Java / OO programmer
– For the Spark developer
– For the Big Data developer
– For the Big Data scientist / mathematician
– For the system architect
38. 38Intro to Spark: Intro to Scala | 7/9/2014
Scala for the Big Data developer
• Spark
– Programming API in Scala
– Implemented in Scala
• Scalding
– Scala DSL on top of Cascading
– data processing API and processing query planner used for
defining, sharing, and executing data-processing workflows
– Abstractions: tuples, pipes, source/sink taps
• Algebird
• Summingbird
– Library that lets you write MapReduce programs that look like
native Scala or Java collection transformations
– Execute them on a number of well-known distributed MapReduce
platforms, including Storm and Scalding.
39. 39Intro to Spark: Intro to Scala | 7/9/2014
Outline
• Spark
– Hadoop eco system
• Scala
– Background
• Why Scala?
– For the computer scientist
– For the Java / OO programmer
– For the Hadoop/Spark developer
– For the Big Data developer
– For the Big Data scientist / mathematician
– For the system architect
40. 40Intro to Spark: Intro to Scala | 7/9/2014
Scala for the Big Data scientist / mathematician
• Monoid
– If you want to “attach” operations such as +, -, *, / or <= to data
objects (e.g., Bloom filters), then you want to provide monoid forms
of those data objects
– Consists of
• A set of objects
• Binary operation that satisfies the monoid axioms
• Monad
– If you want to create a data processing pipeline that transforms the
state of a data object
– composition
41. 41Intro to Spark: Intro to Scala | 7/9/2014
Outline
• Spark
– Hadoop eco system
• Scala
– Background
• Why Scala?
– For the computer scientist
– For the Java / OO programmer
– For the Hadoop/Spark developer
– For the Big Data developer
– For the Big Data scientist / mathematician
– For the system architect
42. 42Intro to Spark: Intro to Scala | 7/9/2014
Scala for the system architect
• Concurrency
• Problem:
– Threads
– Shared mutable state
– Locks,
• Solution:
– message passing concurrency w/ Actors
– Future, Promise
• Abstractions
– Actor
• an object that processes a message
• encapsulates state (state not shared)
– ActorRef
– Message, usually sent asynchronously
– Mailbox
– ActorSystem
43. 43Intro to Spark: Intro to Scala | 7/9/2014
Scala for the system architect: Akka
• Fault tolerance
– Supervision
– Strategies
• Resume, restart, stop, escalate, …
• Scale out: remote actors
– Via configuration
47. 47Intro to Spark: Intro to Scala | 7/9/2014
Outline
• Spark
– Hadoop eco system
• Scala
– Background
• Why Scala?
– For the computer scientist
– For the Java / OO programmer
– For the Spark developer
– For the Big Data developer
– For the Big Data scientist / mathematician
– For the system architect
48. 48Intro to Spark: Intro to Scala | 7/9/2014
Different perspectives on an elephant Scala
49. 49Intro to Spark: Intro to Scala | 7/9/2014
Spark in the Hadoop ecosystem
50. 50Intro to Spark: Intro to Scala | 7/9/2014
References
• http://scala-lang.org/
• Scala in Action, Nilanjan Raychaudhuri
• Grokking Functional Programming, Aslam Khan
• Michael Noll
51. Intro to Apache Spark:
Fast cluster computing engine for
Hadoop
Intro to Scala:
Object-oriented and functional
language for the Java Virtual
Machine
ACM SIGKDD, 7/9/2014
Roger Huang
Lead System Architect
Digital & Mobile Products Architecture
rohuang@visa.com
rog4096@yahoo.com