Среда Разработки в IBM

Intro to Event-Driven Design with JavaScript

Agenda

●Basics and EDA intro

● Foreplay Basic knowledge about functions in JavaScript

●Code writing

The three styles of interaction

Type of interaction Initiator Participants

Time-driven Time The specified system

Request-driven Client Client and Server

Event-driven Event Open-ended

Time driven

Fruit system

run inventory check every 60 mins

Request driven

Tarzan Fruit systemMe want three banans!

Event driven

Fruit system “Tarzan took

three bananas”

“Fruit system is low on

bananas”

5 Principles of EDA

●“Real-time” events as they happen at the producer

●Push notifications

●One-way “fire-and-forget”

●Immediate action at the consumers

●Informational (“someone logged in”), not commands (“audit this”)

Typical EDA architecture

system system system

system system system

Event Bus

Event Poducer

Event Transport

Event Consumers

Main benefits of EDA

●Better service (no batch, less waiting)

●No point-to-point integration (fire & forget)

●High performance, highly scalable systems

The birth of system

Inventory

Customer

Shop

The monolith

Inventory

Customer

Shop

NewsletterReporting

Payment

SOA architecture

Shop Payment

Newsletter

Inventory

Customer Reporting

Divide the problem domains into separate systems

SOA architecture

Shop Payment

Newsletter

Inventory

Customer Reporting

A lot of point to point integration...

SOA + EDA =

Shop Payment

Newsletter

Inventory

Customer Reporting

Event Bus 3th system

Core

[Observer’s minimum]

1.Publisher

2.Message

3.Subscriber

4.Emitter

5.*Topics

Simple EDD implementation

MESSAGE

MESSAGE

MESSAGE

Simple Example

EmitterPublisher

Subscriber

Subscriber

Publisher/Subscriber

MESSAGE

JS Functions

Context. This.var typicalAmerican = { firstName: “John”, lastName: “Smith”, sayYourName: function(){ return "My name is " + this.firstName + ‘ ’ + this.lastName; }}

typicalAmerican.sayYourName(); //My name is John Smith

Context. This.var typicalAmerican = { firstName: “John”, lastName: “Smith”, sayYourName: function(){ return "My name is " + this.firstName + ‘ ’ + this.lastName; }}

var typicalAmericansName = typicalAmerican.sayYourName;

typicalAmericansName(); //My name is undefined undefined

typicalAmericansName.call({firstName: “Rud”, lastName: “Man”}); //My name is Rud Man

Function#call(context)

JS Functions

JS Functions

Context. This.var typicalAmerican = { firstName: “John”, lastName: “Smith”, sayYourName: function(middleName){ return "My name is " + this.firstName + ‘ ’ + middleName + ' ' + this.lastName; return ['My name is', this.firstName, middleName, this.lastName].join(' '); }}

var typicalAmericansName = typicalAmerican.sayYourName;typicalAmericansName.call({firstName: “Rud”, lastName: “Man”}, “Arm”); //My name is Rud Arm Man

Use the join, Luke

Function#call(context[, arg1[, arg2...]])

JS Functions

Argumentsfunction Point(x, y){ this.coords = [x, y]; this.distanceTo = function(x, y){ var sqrt = Math.sqrt abs = Math.abs, point=[x, y]; return sqrt(sqrt(abs(this.coords[0] - point[0])) + sqrt(abs(this.coords[1] - point[1]))); }}

var point = new Point(0, 0);point.distanceTo(1,1); //1.41...

JS Functions

what about multiplay arguments?function Point(x, y, ...){}

function Point(){ this.coords = arguments; // arguments == [x, y, ...] this.distanceTo = function(){ var sqrt = Math.sqrt abs = Math.abs, res = 0, point = arguments; for(var i=0, len=coords.length; i<len; ++i){ res += sqrt(abs(this.coords[i] - point[i])); } return sqrt(res); }}

var point = new Point(1, 1);point.distanceTo(0, 0); //1.41..

Time to coding!

Links

Mediator pattern - http://largescalejs.ru/the-mediator-pattern/(how to remove subscription see in comments ;)

Context in JS (this, #call and #apply) - https://learn.javascript.ru/call-apply

Event Driven Architecture by Stefan Norberg on SlideShare - http://www.slideshare.net/stnor/event-driven-architecture-3395407