A Journey to Reactive Function Programming

A JOURNEY INTO REACTIVE FUNCTIONAL PROGRAMMING

Ahmed Solimanأحمد سليمان

• CAT Reloaded Co-founder

• Life-long architect, software, and systems engineer.

• Focusing on systems reliability, scalability, and clean code.

Conictus

WHAT IS REACTIVE PROGRAMMING?

WHY REACTIVE PROGRAMMING?

THE INTERNET IN 2005

2005

• The Internet had 1 billion users.

• Facebook had 5.5 million users.

• YouTube was a new born.

• Netflix had yet to introduce video streaming (2007)

https://medium.com/reactive-programming/what-is-reactive-programming-bc9fa7f4a7fc

THE INTERNET IN 2015

• The internet has 2.95 billion users.

• Facebook has 1.393 billion monthly active users.

• YouTube has 1 billion users with 6 billions of hours of video/month.

• Twitter has 270 million users.

• Netflix has 57.4 million digital subscriber with 1 billion hours of video/month

JUST TOO DAMN FAST!

WHAT REALLY IS REACTIVE PROGRAMMING?

• A set of ideas and principles to manage complexity in the world of highly responsive, asynchronous, scalable applications.

• The goal of reactive programming is to build responsive, flexible, and highly scalable applications without managing the complexity

REACTIVE SYSTEMS

Message-driven

ResilientElastic

Responsive

• The system responds in a timely manner if at all possible.

• Responsive systems focus on providing rapid and consistent response times, establishing reliable upper bounds so they deliver a consistent quality of service.

Responsive

Responsiveness is the cornerstone of usability and utility, but more than that, responsiveness means that problems may be detected quickly and dealt with effectively.

BOUNDED LATENCYResponsive

CIRCUIT BREAKER

Circuit Breaker Backend ServiceClient X

BOUNDED QUEUES

Queue Backend ServiceClient

Average Latency = Queue Size x Duration Per Op

Failure is First Class

Resilient

Responsive in the face of failure!

This applies not only to highly-available, mission critical systems — any system that is not resilient will be unresponsive after a failure.

Resilient

Resilient

Containment and Isolation

• Recovery of each component is delegated to another (external) component and high-availability is ensured by replication where necessary.

Response in the face of Changing load

Elastic

PARTITIONING/SHARDING

Consistent HashingRouter

Bucket 1

Bucket 2

Bucket 100

Bucket 101

Machine 1

Machine (N)

msg

SHARE NOTHING

• Message-driven architectures are share-nothing by design.

• No shared mutable state between components.

• Avoid single-point-of-failures by partitioning+replication.

SCALE UP/DOWN AND OUT/INProcess 1

Process 2

MachineProcess 3

Process 4

…

Process 1

Process 2Server 1

Process 1

Process 2Server 1

Process 1

Process 2Server 1

LOCATION TRANSPARENCY

AuthService x = getAuthService(/* local or remote*/)x.sendMessage(new Login("asoliman", "password"))

• Abstraction over location of components enables you to scale out and up in the same way.

• The underlying message-passing system should handle all the plumbing and the optimization for the message delivery

• Foundation of scalable, resilient, and ultimately responsive systems.

• Immutable by design

• Loose Coupling

• Location Transparency

• Concurrency Control

• Everything is a stream of messages

Message-driven

WHAT REACTIVE PROGRAMMING ISN’T

• A programming language

• A framework/library/tool

• The only way to achieve concurrency and interactive applications

WHAT IS FUNCTIONAL AND WHY?

• Programming with functions where functions and data are treated the same way.

• A program is an evaluation of mathematical functions.

• Avoids mutable-data and changing-state.

function getEvens() { var x = 1; var result = []; while (x < 10) { if (x % 2 == 0) { result.push(x * 2); } } return result;}

scala> Stream.from(1) .takeWhile(x => x < 10) .filter(x => x % 2 == 0) .map(x => x * 2) .toListres2: List[Int] = List(4, 8, 12, 16)

LET’S ADD TIMEThe World is a set of Observable<T>

takeWhile filter map

dropWhile map

filter

Observable Reduce

LET’S SEE SOME CODE

THINGS TO WATCH

http://reactivemanifesto.org/

LET’S REACH OUT

AhmedSoliman!"

THANK YOU!