Models, Modules, and Microservices

Starring With Directed by In the role of Also Starring

H3NN1NG

Schw3ntn3r

@hschwentner

Foto: Steindy/Wikipedia

@hschwentner Do I get a car for this?

CUSTOMER TELLS WISH FOR 1 SALESPERSON SIGNS TO GIVES FOR
CONTRACT 3 RISIK MANAGER CONTRACT PASSES ON TO 4 CONTRACT VOTES CHECKS CALCULATES 5 6 7 CALCU- LATES TO 8 2 CAR CREDIT RATING INSTALLMENT CAR RESALE VALUE CONTRACT

@hschwentner How do we design a program for that?

@hschwentner #dddesign

@hschwentner Was ist das für 1 Design?

@hschwentner Vong Domain her

-DRIVEN DESIGN

Software Domain

CUSTOMER SIGNS CONTRACT 3 RISK MANAGER CONTRACT VOTES 7 <<Entity>>
LeasingContract sign() vote()

<<Entity>> LeasingContract sign() vote()

Object orientation

<<Entity>> LeasingContract sign() vote() extend() terminate() sell_to_refinance() ...

@hschwentner The One Big Model

@hschwentner Reality: Not one big model But several mixed models

BBOM Foto: Benutzer:Summi/Wikipedia/CC-BY-SA-3.0-migrated

@hschwentner “Whoever uses a canonical model has lost control over
his life.” – Karl Lagerfeld

@hschwentner »Wer ein unternehmensweites Modell einsetzt, hat die Kontrolle über
sein Leben verloren« – Karl Lagerfeld

@hschwentner Why is that?

@hschwentner Too Big to be understood as a whole

@hschwentner Model?

A tool to understand the world

CUSTOMER TELLS WISH FOR 1 SALES-PERSON SIGNS TO GIVES FOR
CONTRACT 3 RISIK MANAGER CONTRACT PASSES ON TO 4 CONTRACT VOTES CHECKS CALCULATES 5 6 7 CALCU- LATES TO 8 2 CAR CREDIT RATING INSTALLMENT CAR RESALE VALUE CONTRACT SALES RISK MANAGMENT

<<Entity>> LeasingContract sign() vote() ✘

<<Entity>> LeasingContract sign() <<Entity>> LeasingContract vote()

<<Entity>> LeasingContract sign() <<Entity>> LeasingContract vote() SALES RISK MANAGEMENT

Bounded Context

<<Entity>> LeasingContract sign() <<Entity>> LeasingContract vote() SALES RISK MANAGEMENT

@hschwentner Clear Boundaries

@hschwentner Code Team Database

@hschwentner Strategic Design

Team Head Team Tail Team Body Team Legs

Team Emma Team Berta Team Erna Team Lisl

<<Entity>> LeasingContract sign() <<Entity>> LeasingContract vote()

@hschwentner Implementing Multiple Models

@hschwentner JVM: Packages Jigsaw-Modules

@hschwentner .NET: DLLs

@hschwentner PHP: Namespaces

@hschwentner JavaScript: Revealing Module Pattern TypeScript: Modules

@hschwentner Generally: Microservices Self-Contained Systems Verticals

@hschwentner Multiple Models in Java

@hschwentner How?

Packages

@hschwentner 1 bounded context = 1 package

package leasingninja.sales; class LeasingContract { /*...*/ } package leasingninja.riskmanagement; class
LeasingContract { /*...*/ }

<<Entity>> LeasingContract sign() <<Entity>> LeasingContract vote() <<package>> leasingninja.sales <<package>> leasingninja.riskmanagement

Problems: * No real encapsulation * No nesting * only
a logical group of classes

Only public and package private

But: all classes of a bounded context in one package
-> already quite ok

@hschwentner Project Jigsaw

@hschwentner Real capsule

@hschwentner package leasingninja.sales.ui; package leasingninja.sales.domain; package leasingninja.sales.infrastructure;

@hschwentner package leasingninja.sales.ui; package leasingninja.sales.domain; package leasingninja.sales.infrastructure; package leasingninja.sales.api;

@hschwentner /* module-info.java */ module leasingninja.sales { exports leasingninja.sales.api; }

leasingninja.sales.api leasingninja.sales.* Interface Not accessible from outside

@hschwentner /* module-info.java */ module leasingninja.riskmanagement { requires leasingninja.sales; }

RISK MANAGE-MENT SALES

Rule: reverse domain names

@hschwentner /* module-info.java */ module de.wps.leasingninja.sales { exports de.wps.leasingninja.sales.api; }

@hschwentner /* module-info.java */ module de.wps.leasingninja.riskmanagement { requires de.wps.leasingninja.sales; }

@hschwentner Modular JAR

@hschwentner Maybe even better fitting: services mit uses/provides with

@hschwentner Multiple Models in .NET

@hschwentner How?

Assembly

@hschwentner 1 bounded context = 1 DLL

namespace Leasingninja.Sales { class LeasingContract { /*...*/ } } namespace
Leasingninja.Riskmanagement; { class LeasingContract { /*...*/ } }

<<Entity>> LeasingContract sign() <<Entity>> LeasingContract vote() <<Assembly>> Leasingninja.Sales <<Assembly>> Leasingninja.Riskmanagement

@hschwentner Architecture inside a Bounded Context (DLL)

@hschwentner namespace Leasingninja.Sales.UI {} namespace Leasingninja.Sales.Application {} namespace Leasingninja.Sales.Domain {}
namespace Leasingninja.Sales.Infrastructure {}

@hschwentner namespace Leasingninja.Sales.UI {} namespace Leasingninja.Sales.Application {} namespace Leasingninja.Sales.Domain {}
namespace Leasingninja.Sales.Infrastructure {} namespace Leasingninja.Sales {}

@hschwentner namespace Leasingninja.Sales.Domain { [Entity] internal class LeasingContract { /*...*/
} } namespace Leasingninja.Sales { [DomainEvent] public class ContractSigned { /*...*/ } }

Leasingninja.Sales Leasingninja.Sales.UI Leasingninja.Sales.Application Leasingninja.Sales.Domain Leasingninja.Sales.Infrastructure Interface Not accessible from outside

@hschwentner Multiple Models in PHP

@hschwentner How?

Namespace

@hschwentner 1 bounded context = 1 namespace

<?php namespace Leasingninja\Sales; class LeasingContract { /*...*/ } > <?php
namespace Leasingninja\Riskmanagement; class LeasingContract { /*...*/ } >

FQCN (Fully qualified class name = full namespace + class
name)

<<Entity>> LeasingContract sign() <<Entity>> LeasingContract vote() <<Namespace>> Leasingninja.Sales <<Namespace>> Leasingninja.Riskmanagement

Problems: * No encapsulation * only a logical group of
classes

But: all classes of a bounded context in one namespace
-> better than nothing

@hschwentner Architecture inside a Bounded Context

@hschwentner namespace Leasingninja\Sales\UI; namespace Leasingninja\Sales\Application; namespace Leasingninja\Sales\Domain; namespace Leasingninja\Sales\Infrastructure;

@hschwentner namespace Leasingninja\Sales\UI; namespace Leasingninja\Sales\Application; namespace Leasingninja\Sales\Domain; namespace Leasingninja\Sales\Infrastructure; namespace
Leasingninja\Sales;

Leasingninja.Sales Leasingninja.Sales.UI Leasingninja.Sales.Application Leasingninja.Sales.Domain Leasingninja.Sales.Infrastructure Interface (should) not be accessible
from outside

Convention: Access only 1 dot 2 dot only in same
BC

@hschwentner Multiple Models with Microservices

Distributed System

Fallacies of distributed computing: The network is reliable. Latency is
zero. Bandwidth is infinite. The network is secure. Topology doesn't change. There is one administrator. Transport cost is zero. The network is homogeneous.

Verticals Self-Contained Systems Microservices

Micro- service A Presentation Domain Infrastructure Application Micro- service B
Direct Access to DB Micro- service C

@hschwentner Independent Deployability

RISK MANAGE-MENT

@hschwentner Core Domain

@hschwentner How to split the monolith

1) How should it be? 2) How is it? 3)
How to move the “is” to the “ideal”? RISK MANAGE- MENT SALES

1) How should it be? 1) Collaborative Modelling 2) “ideal”
context map 2) How is it? 1) Architecture Analysis 2) As-is context map 3) How to move the “is” to the “ideal”? 1) Extract a supporting domain to learn 2) Then extract core(s)

<<Entity>> LeasingContract sign() vote() SALES RISK MANAGEMENT <<Entity>> LeasingContract sign()
vote() BIG BALL OF MUD <<Entity>> LeasingContract sign() vote()

@hschwentner Always Microservices?

Simon Brown

Distributed Big Ball Of Mud Modulith Microservices Monolithic Big Ball
Of Mud

@hschwentner Consulting

@hschwentner Team organization

“Organizations which design systems are constrained to produce designs which
are copies of the communication structures of these organizations.” Melvin Conway

Melvin Conway (1967) “Organizations which design systems are constrained to
produce designs which are copies of the communication structures of these organizations.”

“The organization of the software and the organization of the
software team will be congruent.” Eric Raymond

“If you have four groups working on a compiler, you'll
get a 4-pass compiler.” Eric Raymond

@hschwentner Conclusion

1. Model your domain 2. Split => several models (3.
Distribute models)

Strategic Design must Microservices can

@hschwentner Further Reading

@hschwentner LeasingNinja.io

@hschwentner speakerdeck.com/hschwentner

Foto: H. Schwentner

Foto: Amazon

15$ online: leanpub.com/domainstorytelling Frag mich nach Deiner Kopie Einführung mit
allem was man wissen muss Überblick Rabatt! https://leanpub.com/domainstorytelling/c/wjax2019

@hschwentner What now?

@hschwentner Consulting

Workshop Domain-Driven Design concrete wps.de/ddd

@hschwentner Foto: Henning Schwentner

@hschwentner FEEDBACK

Henning Schwentner @hschwentner [email protected] DDD DDD Slides: speakerdeck.com/hschwentner Book: leanpub.com/domainstorytelling

Models, Modules, and Microservices

Models, Modules, and Microservices

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