Downloaded 12 times
![Composition
def fetchUser(id: Long): Option[User] = ...
def fetchCar(id: Long): Option[Car] = ...
val carPrice: Option[BigDecimal] = for {
user <- fetchUser(42)
car <- fetchCar(23)
} yield {
user.age + car.price
}](https://image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-35-2048.jpg)
![Composition
def fetchUser(id: Long): Future[User] = ...
def fetchCar(id: Long): Future[Car] = ...
val carPrice: Future[BigDecimal] = for {
user <- fetchUser(42)
car <- fetchCar(23)
} yield {
user.age + car.price
}](https://image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-36-2048.jpg)
![Composition
def fetchUser(id: Long): Try[User] = ...
def fetchCar(id: Long): Try[Car] = ...
val carPrice: Try[BigDecimal] = for {
user <- fetchUser(42)
car <- fetchCar(23)
} yield {
user.age + car.price
}](https://image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-37-2048.jpg)
![Composition
def fetchUser(id: Long): [User] = ...
def fetchCar(id: Long): [Car] = ...
val carPrice: [BigDecimal] = for {
user <- (42)
car <- (23)
} yield {
user.age + car.price
}](https://image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-38-2048.jpg)
![Sending and receiving messages
case class Script(text: String)
class AudreyHepburn extends Actor {
def receive = {
case Script(text) =>
read(text)
}
}
val audrey = ActorSystem.actorOf(Props[Audrey])
audrey ! Script(breakfastAtTiffany)](https://image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-60-2048.jpg)
![Supervision
class HollyCrazyCatLady extends Actor {
lazy val cats: ActorRef = context
.actorOf[Cat]
.withRouter(
RoundRobinRouter(nrOfInstances = 42)
)
}](https://image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-61-2048.jpg)
![Supervision
class HollyCrazyCatLady extends Actor {
lazy val cats: ActorRef = context
.actorOf[Cat]
.withRouter(
RoundRobinRouter(nrOfInstances = 42)
)
override def supervisorStrategy =
OneForOneStrategy(maxNrOfRetries = 3) {
case t: Throwable =>
log.error("A cat had a problem!",
t)
Restart
}
}](https://image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-62-2048.jpg)
![Composition
def fetchUser(id: Long): Option[User] = ...
def fetchCar(id: Long): Option[Car] = ...
val carPrice: Option[BigDecimal] = for {
user <- fetchUser(42)
car <- fetchCar(23)
} yield {
user.age + car.price
}](https://crownmelresort.com/image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-35-2048.jpg)
![Composition
def fetchUser(id: Long): Future[User] = ...
def fetchCar(id: Long): Future[Car] = ...
val carPrice: Future[BigDecimal] = for {
user <- fetchUser(42)
car <- fetchCar(23)
} yield {
user.age + car.price
}](https://crownmelresort.com/image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-36-2048.jpg)
![Composition
def fetchUser(id: Long): Try[User] = ...
def fetchCar(id: Long): Try[Car] = ...
val carPrice: Try[BigDecimal] = for {
user <- fetchUser(42)
car <- fetchCar(23)
} yield {
user.age + car.price
}](https://crownmelresort.com/image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-37-2048.jpg)
![Composition
def fetchUser(id: Long): [User] = ...
def fetchCar(id: Long): [Car] = ...
val carPrice: [BigDecimal] = for {
user <- (42)
car <- (23)
} yield {
user.age + car.price
}](https://crownmelresort.com/image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-38-2048.jpg)
![Sending and receiving messages
case class Script(text: String)
class AudreyHepburn extends Actor {
def receive = {
case Script(text) =>
read(text)
}
}
val audrey = ActorSystem.actorOf(Props[Audrey])
audrey ! Script(breakfastAtTiffany)](https://crownmelresort.com/image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-60-2048.jpg)
![Supervision
class HollyCrazyCatLady extends Actor {
lazy val cats: ActorRef = context
.actorOf[Cat]
.withRouter(
RoundRobinRouter(nrOfInstances = 42)
)
}](https://crownmelresort.com/image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-61-2048.jpg)
![Supervision
class HollyCrazyCatLady extends Actor {
lazy val cats: ActorRef = context
.actorOf[Cat]
.withRouter(
RoundRobinRouter(nrOfInstances = 42)
)
override def supervisorStrategy =
OneForOneStrategy(maxNrOfRetries = 3) {
case t: Throwable =>
log.error("A cat had a problem!",
t)
Restart
}
}](https://crownmelresort.com/image.slidesharecdn.com/voxxeddays-reactivewhyhow-150218025021-conversion-gate01/75/Voxxed-Days-Vienna-The-Why-and-How-of-Reactive-Web-Applications-on-the-JVM-62-2048.jpg)
Uploaded byManuel Bernhardt
Voxxed Days Vienna - The Why and How of Reactive Web-Applications on the JVM
The document discusses the need for reactive and functional programming approaches to build scalable applications that can take advantage of many-core processors and distributed systems. It introduces key concepts like immutability, functions, and declarative programming. Specific frameworks like Scala, Play and Akka are presented as tools that support this reactive, functional style for building web applications that can horizontally scale across multiple cores and nodes. The talk promotes adopting these approaches to build systems that can better handle concurrency, distribution and failure.
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Voxxed Days Vienna - The Why and How of Reactive Web-Applications on the JVM
- 2. Agenda 1. Why Reactive? 2.Functional programming 3. Scala 4. Play 5. Akka
- 3. Who is speaking? •freelance software consultant based in Vienna • Vienna Scala User Group • web, web, web
- 4. Who is speaking? •freelance software consultant based in Vienna • Vienna Scala User Group • web, web, web • writing a book on reactive web- applications http://www.manning.com/ bernhardt
- 5.
- 6. Welcome to 2015 It's2015! And yet we don't have flying cars...
- 7. But we havemany- core CPUs • Tilera, Cavium • Adapteva Parallela • Xeon PHI • It's happening!
- 8. Too many cores? •"640 kb ought to be enough for anybody" ~ Bill Gates
- 9. Too many cores? •"640 kb ought to be enough for anybody" ~ Bill Gates • "4 cores ought to be enough for anybody" ~ Linus Torvalds1 1 http://highscalability.com/blog/2014/12/31/linus-the-whole-parallel- computing-is-the-future-is-a-bunch.html
- 11. Programming with many cores •serial approach does not work • asynchronous programming with inappropriate tools does not work drives people insane • we need (and already have) new abstractions • we have to re-evaluate the use of our old abstractions
- 12. The problem withmutable state car.setPosition(0); car.setPosition(10);
- 13. The problem withmutable state
- 14. The problem with mutablestate • there is no notion of time, only an illusion thereof • changes to a mutable model only make sense locally if nobody is watching • the larger the scope, the harder it gets to prevent inconsistencies
- 15. The problem with locks •solution workaround for a broken conceptual model • hard to reason about • performance hit
- 16. Distribution is necessary * *unless you have a lot of money
- 17. Let's make things evenmore complicated: programming with many nodes • scaling out to handle large loads • scaling out / replication to handle node failure
- 18. Let's make things evenmore complicated: programming with many nodes • scaling out to handle large loads • scaling out / replication to handle node failure • problem: networks fail
- 19. Failure is inevitable •Jepsen series3 • CAP theorem • transactions don't really work that way in distributed systems 3 http://aphyr.com
- 20. Hard problem to solve •Paxos: Consensus solving protocols • CQRS: Command Query Responsibility Segregation • CRDTs: Commutative Replicated Data Types
- 21.
- 22. Imperative programming In imperative programmingyou describe how something is done
- 23. Imperative programming In imperative programmingyou describe how something is done Example: List<User> users = ... List<User> minors = new ArrayList<User>(); List<User> majors = new ArrayList<User>(); for(int i = 0; i < users.size(), i++;) { User u = users.get(i); if(u.getAge() < 18) { minors.add(u); } else { majors.add(u); } }
- 24. Declarative programming In declarative programmingyou describe what you want to get
- 25. Declarative programming In declarative programmingyou describe what you want to get Example: val (minors, majors) = users.partition(_.age < 18)
- 26. Declarative programming In declarative programmingyou describe what you want to get Example: val (minors, majors) = users.partition(_.age < 18) Declarative programming is like driving with a GPS navigation system You can do without, but it's so comfortable
- 27. Core concepts ofFP • immutability • functions • transforming data with functions
- 28. Immutability case class Car(brand:String, position: Int) val car = Car(brand = "DeLorean", position = 0) val movedCar = car.copy(position = 10)
- 29. Immutability case class Car(brand:String, position: Int) val car = Car(brand = "DeLorean", position = 0) val movedCar = car.copy(position = 10)
- 30. Immutability case class Car(brand:String, position: Int) val car = Car(brand = "DeLorean", position = 0) val movedCar = car.copy(position = 10)
- 31. Functions and higher-order functions val(minors, majors) = users.partition(_.age < 18)
- 32. Functions and higher-order functions valisMinor = (age: Int) => age < 18 val (minors, majors) = users.partition(isMinor)
- 33. Functions and higher-order functions valisMinor = (age: Int) => age < 18 val (minors, majors) = users.partition(isMinor) Moving behaviour around instead of moving data around
- 34. Transforming data val addresses= users.filter(_.age > 18) .map(_.address) .sortBy(_.city) Goal: To build increasingly complex behaviour through a series of transformations / by composing functions
- 35. Composition def fetchUser(id: Long):Option[User] = ... def fetchCar(id: Long): Option[Car] = ... val carPrice: Option[BigDecimal] = for { user <- fetchUser(42) car <- fetchCar(23) } yield { user.age + car.price }
- 36. Composition def fetchUser(id: Long):Future[User] = ... def fetchCar(id: Long): Future[Car] = ... val carPrice: Future[BigDecimal] = for { user <- fetchUser(42) car <- fetchCar(23) } yield { user.age + car.price }
- 37. Composition def fetchUser(id: Long):Try[User] = ... def fetchCar(id: Long): Try[Car] = ... val carPrice: Try[BigDecimal] = for { user <- fetchUser(42) car <- fetchCar(23) } yield { user.age + car.price }
- 38. Composition def fetchUser(id: Long):[User] = ... def fetchCar(id: Long): [Car] = ... val carPrice: [BigDecimal] = for { user <- (42) car <- (23) } yield { user.age + car.price }
- 39. Maths FTW! • Option,Future, Try all implement monadic operations2 • set of data structures following the same laws • know one, know them all • keeping things DRY • also, it's not that scary 2 https://www.haskell.org/haskellwiki/Monad_tutorials_timeline
- 40.
- 41. History • Martin Odersky,EPFL • first release in 2003 • Typesafe Inc.
- 42. Design goals • Fullinteroperability with Java • Cut down boilerplate • Pure object orientation & functional programming • Move away from null • Many-core programming
- 44. If I wereto pick a language today other than Java, it would be Scala. — James Gosling
- 45. Scala in Vienna •Monthly Meetup • http://scala-vienna.org • Next meetup on 18th of February
- 46.
- 47. Play history • MVCframework, inspired by RoR, Django, Symfony • Zenexity • first version released in 2009 • version 2.0 released in 2012, core rewritten in Scala
- 48. Design Principles • everythingis compiled • non-blocking I/O • controller actions are functions (request => response) • "share nothing" => horizontal scalability
- 49. Threaded servers • likea train station with multiple tracks • station chief decides which trains go on which platform • if there are more trains than platforms, trains queue up • if too many trains are queuing up, huge delays occur and passengers go home
- 50. Evented servers • likea waiter in a restaurant • runs back and forth between tables and the kitchen • does only small tasks that do not take much time • one server can each serve many tables at once
- 51. Advantages of theevented approach • less threads means less memory • better CPU utilization (reduced context switching) • (much) higher throughputs than threaded servers
- 53. History • first releasein January 2010 • based on the Actor model (Erlang) • message-based asynchronous concurrency toolkit • object-oriented programming done right
- 54. History • first releasein January 2010 • based on the Actor model (Erlang) • message-based asynchronous concurrency toolkit • object-oriented programming done right • Akka is also a mountain in Sweden
- 55. Actors • lightweight objects •send and receive messages (mailbox) • can have children (supervision)
- 59. Sending and receivingmessages case class Script(text: String) class AudreyHepburn extends Actor { def receive = { case Script(text) => read(text) } }
- 60. Sending and receivingmessages case class Script(text: String) class AudreyHepburn extends Actor { def receive = { case Script(text) => read(text) } } val audrey = ActorSystem.actorOf(Props[Audrey]) audrey ! Script(breakfastAtTiffany)
- 61. Supervision class HollyCrazyCatLady extendsActor { lazy val cats: ActorRef = context .actorOf[Cat] .withRouter( RoundRobinRouter(nrOfInstances = 42) ) }
- 62. Supervision class HollyCrazyCatLady extendsActor { lazy val cats: ActorRef = context .actorOf[Cat] .withRouter( RoundRobinRouter(nrOfInstances = 42) ) override def supervisorStrategy = OneForOneStrategy(maxNrOfRetries = 3) { case t: Throwable => log.error("A cat had a problem!", t) Restart } }
- 63. Actors out there •remoting • clustering • persistent actors event sourcing
- 64. CQRS • high level:separate writes & reads (performance) • transform and store everything as events (write only) • transform into query model in a separate store Immutability (again!)
- 65. Summary • many-core ishere to stay • FP is essential to take advantage of many-core systems
- 66. Summary • many-core ishere to stay • FP is essential to take advantage of many-core systems • Play and Akka make it possible to build web-applications that can scale in and out
- 67. Thank you http://www.manning.com/bernhardt code mlbernhardt50% discount Questions? http://scala-vienna.org 18th of February Join the dark side, we have free drinks