Models, Modules, and Microservices

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Starring With Directed by In the role of Also Starring

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H3NN1NG

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Schw3ntn3r

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@hschwentner

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Foto: Steindy/Wikipedia

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@hschwentner Do I get a car for this?

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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

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@hschwentner How do we design a program for that?

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@hschwentner #dddesign

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@hschwentner Was ist das für 1 Design?

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@hschwentner Vong Domain her

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-DRIVEN DESIGN

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Software Domain

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

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<> LeasingContract sign() vote()

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Object orientation

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

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@hschwentner The One Big Model

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

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

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

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

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@hschwentner Why is that?

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@hschwentner Too Big to be understood as a whole

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@hschwentner Model?

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A tool to understand the world

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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

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<> LeasingContract sign() vote() ✘

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

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

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Bounded Context

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

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@hschwentner Clear Boundaries

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@hschwentner Code Team Database

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@hschwentner Strategic Design

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✘

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Team Head Team Tail Team Body Team Legs

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Team Emma Team Berta Team Erna Team Lisl

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

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@hschwentner Implementing Multiple Models

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@hschwentner JVM: Packages Jigsaw-Modules

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@hschwentner .NET: DLLs

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@hschwentner PHP: Namespaces

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@hschwentner JavaScript: Revealing Module Pattern TypeScript: Modules

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@hschwentner Generally: Microservices Self-Contained Systems Verticals

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@hschwentner Multiple Models in Java

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@hschwentner How?

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Packages

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@hschwentner 1 bounded context = 1 package

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

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

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

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Only public and package private

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

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@hschwentner Project Jigsaw

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@hschwentner Real capsule

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

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

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

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

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

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RISK MANAGE-MENT SALES

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Rule: reverse domain names

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

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

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@hschwentner Modular JAR

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

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@hschwentner Multiple Models in .NET

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@hschwentner How?

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Assembly

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@hschwentner 1 bounded context = 1 DLL

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

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

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@hschwentner Architecture inside a Bounded Context (DLL)

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

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

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

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

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RISK MANAGE-MENT SALES

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@hschwentner Multiple Models in PHP

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@hschwentner How?

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Namespace

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@hschwentner 1 bounded context = 1 namespace

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

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

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

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

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@hschwentner Architecture inside a Bounded Context

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

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

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

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

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RISK MANAGE-MENT SALES

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@hschwentner Multiple Models with Microservices

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Distributed System

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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.

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Verticals Self-Contained Systems Microservices

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

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@hschwentner Independent Deployability

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Team Emma Team Berta Team Erna Team Lisl

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Team Emma Team Berta Team Erna Team Lisl

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Team Emma Team Berta Team Erna Team Lisl

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RISK MANAGE-MENT SALES

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RISK MANAGE-MENT

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RISK MANAGE-MENT SALES

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@hschwentner Core Domain

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Team Emma Team Berta Team Erna Team Lisl

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Team Emma Team Berta Team Erna Team Lisl

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RISK MANAGE-MENT SALES

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@hschwentner How to split the monolith

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

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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)

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

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@hschwentner Always Microservices?

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Simon Brown

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

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@hschwentner Consulting

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@hschwentner Team organization

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

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

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

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

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@hschwentner Conclusion

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

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Strategic Design must Microservices can

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@hschwentner Further Reading

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@hschwentner LeasingNinja.io

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@hschwentner speakerdeck.com/hschwentner

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Foto: H. Schwentner

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Foto: H. Schwentner

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Foto: Amazon

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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

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@hschwentner What now?

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@hschwentner Consulting

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Workshop Domain-Driven Design concrete wps.de/ddd

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@hschwentner Foto: Henning Schwentner

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@hschwentner FEEDBACK

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