Back Day - REX Société Générale - Explorer les principes de l'Event Sourcing

Construire le SI de demain

REX Société Générale La simplicité comme moyen d'être

performant, résilient et de réduire le Time To Market

Marie-Laure Thuret

@mlthuret

Développeur chez

Clément Héliou

@c_heliou

Développeur chez

ThierryAbaléa

@ThierryAbalea

Tech Leadà la

Société Générale

Palladium

Commodity Trading Company

Today

Hedging



Few Months Later

Hedging

Physical Delivery

Sales PersonCustomer Trader

Booking

Exchanges

Automatize the processus

OrchestratorCustomer ExchangesPricer

Booking

Hedger

Trading LimitMargin

The Constraints

Reliability / Resilience Performance

Productivity / Time To Market

Our Solution

Simplicity

Simple ≠ Easy

Choices are business-oriented

Functional and Code

Reduce the impedance between

Our Goal

Orchestration

Let’s take an example with our main component

Event Sourcing

« Capture all changes to an application state as a

sequence of events »Martin Fowler

Date Money Out Money In

2015/05/14 100

2015/05/14 -20

2015/05/16 -30

2015/05/24 380

2015/06/01 -70

Total -120 480

Balance 360

WithdrawalPerformed

accountId: 9387amount: 30€

BankAccount

id: 9387balance: 0€

WithdrawalPerformed


DepositPerformed


BankAccount


BankAccount


BankAccount


Inspired by B. Reitzammer & J. Seitz - http://ookami86.github.io/event-sourcing-in-practice

Apply to

Apply to

Apply to

Produces

Produces

Produces

http://ookami86.github.io/event-sourcing-in-practice

J. Chassaing - http://thinkbeforecoding.com/post/2014/01/04/Event-Sourcing.-Draw-it

http://thinkbeforecoding.com/post/2014/01/04/Event-Sourcing.-Draw-it

BankAccount


WithdrawalPerforme


DepositPerformed


BankAccount


Bug


Apply to

Apply to

Produces

Produces


WithdrawalPerformed


BankAccount


WithdrawalPerformed


DepositPerformed


BankAccount


BankAccount



Apply to

Apply to

Produces

Produces


Domain Driven Design

« DDD is about designing software based on models

of the underlying (business) domain »

Martin Fowler

Ubiquitous Language

RepositoryAggregate Root

EntityValue Object

Durable business model

Extensibility

Clean Architecture

Solid Responsibility Segregation

Using Event Sourcing and DDD concepts in

Multiplus

Multiplus Business

Logic

ReceiveQuote{command}

QuoteReceived{event}

QuoteForwarded{event}

Customer

Event Bus

QuoteForwardedHandler{handler}

Quote Requestin Quoting



ForwardQuote{action}

Transaction{aggregate root}

Pricing{entity}

Execution{entity}

Orchestration{entity}

ReceiveQuote{command/value object}

quoteRequestId: 4563price: 100€

QuoteReceived{event/value object}

accountId: 4563price: 110€

- Multiplus Business Logic -

What we’ve learned

Be aware of

Command Sourcing

Multiplus Business

Logic





Multiplus Business

Logic





2015/06/01 Margin: 1%

2015/11/01 Margin: 2%

Multiplus Business

Logic



Customer

Event Bus


{Quote n° 65746}{Quote n° 65746} ??



Multiplus Business

Logic



Customer

Event Bus


Customer gateway

{Quote n° 65746}

{Quote n° 65746}



Store the events produced by the

Decide function

Multiplus Business

Logic





Multiplus Business

Logic

2015/06/01 Margin: 1%

2015/11/01 Margin: 2%



Multiplus Business

Logic



Customer

Event Bus




It’s all in the past !

Date Money Out Money In

2015/05/14 100

2015/05/14 -20

2015/05/16 -30

2015/05/24 30

2015/06/01 -70

Total -120 130

Balance 10

Behavior Driven Development

Conversation

Collaboration

Specifications By Examples

Three Amigos

Automation

Ubiquitous Language

deliverthe rightsoftware

Yourdocumentationwill becomealive

youwill

new comersthank

youwill

new comersthank

… but you’ll enjoy it too !

warning

doing BDD right

easyis not

BDDCommon Issues

Business and developper faces collaboration difficulties

Mess with the scenario writing

Automation Nightmare

our

complexapplication

areoften

we tend to let

everywherebusiness rules

being dispatch

… making them

hard to test

Hexagonal Architecture

the onion architecturethe clean architecture

ports and adapters

Advantages

Testability Flexibility

Business Centric

domain driven app structure

that’s not

enough !

use differentgranularity

business scenarioswhen expressing your

levels

Given a quantity value of 1000 in GWhen the quantity is converted in OZThen the converted quantity is 32.1507 OZ

Given a quote request with a way BUYAnd the credit check request has been sentWhen the credit check response is in errorThen the pricer does not receive a quote requestAnd the platform quote status is REJECTED

Given an authorized product typeWhen the customer sends the rfsThen the pricer receives the rfsWhen the pricer sends a quoteThen the customer receives the quote

Workflow

Feature

Unit

« l’enfer c’est les autres »

Jean-Paul Sartre

at

any timebusiness validation

steroidsintegration testing

on

care aboutthe contract

between your app and another

avoidaccidentalcomplexity

there’s always

implicit

a schemaeven if it’s


DDDEvent Sourcing

BDD

State Machine


Java

DDDEvent Sourcing

BDD

State Machine


DaggerJava

DDDEvent Sourcing

BDD

State Machine


DaggerJava

Guava

DDDEvent SourcingBDD

State Machine

Our architecture is easy to deploy !

Simple

Simple

No More Technologies Than Required

Simple


Business Centric

Simple


Business Centric

Code Understanding is Key

Simple


Business Centric

CourageCode Understanding is Key

Any Questions ?

Back Day - REX Société Générale - Explorer les principes de l'Event Sourcing

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