Software Architecture by Example: Using C# and .NET

Table of Contents....5

About the Author....10

About the Technical Reviewer....11

Acknowledgments....12

Introduction....13

Foreword....16

Chapter 1: The Ticket Sales Problem....18

Background....19

Requirements....20

Options....21

Manual Process....21

Existing System....23

Existing System Considerations....24

Minimum Viable Product....25

Target Architecture....25

How to Deal with High Throughput....26

Widening the Funnel....27

Server....27

Service....27

Multiple Funnels....28

Message Queues....30

Message Brokers....31

Separation of Concerns....33

Target Architecture Diagram....34

Proxy....35

A Note on Cloud Vendors....36

Why Cloud?....37

Examples....38

External APIs....38

Getting Ticket Availability....38

Ordering a Ticket....42

Adding a Message to a Queue....42

Getting a Response from the Queue....43

Summary....46

Chapter 2: The Cash Desk Problem....47

Background....48

Requirements....48

Options....48

Manual Process....49

Target Architecture....52

Audit....52

Event Sourcing....56

Immutable Events....58

How to Change Immutable Events....59

Projections and Snapshots....60

Aggregates....62

CQRS....62

Target Architecture Diagram....63

Examples....65

Persisting Events to Memory....65

Persisting Events to Disk....68

Save....69

Load....71

Writing to Files....76

Summary....77

Chapter 3: The Travel Agent Problem....79

Background....80

Requirements....81

Options....82

Manual Process....82

Transactions....83

ACID....83

Atomic....84

Consistent....84

Isolation....84

Durable....86

Distributed Transactions....87

Possible Scenarios....89

The hospital has no available appointments on that day....89

The space flight provider’s system crashes after receiving a prepare message but before responding....89

The hotel’s system crashes after receiving a commit message and committing the transaction but before acknowledging....89

The transaction coordinator crashes after sending all the prepare messages but before receiving any confirmations....90

Distributed Transaction with Timeout....90

Book and Cancel....91

Hold a Booking....92

Advanced Purchase....92

Business Decision....92

Target Architecture....93

Stateful Service....95

Distributed Service....95

Target Architecture Diagram....95

Examples....96

Project Structure....96

Service Bus Configuration....98

Coordinator....101

Summary....106

Chapter 4: The Social Media Problem....108

Background....109

Requirements....109

Options....110

Manual Process....111

CQRS....112

Benefits....112

Drawbacks....114

Consistency Models....115

Strong or Strict Consistency....116

Sequential or Causal Consistency....116

Weak or Eventual Consistency....117

Target Architecture....117

Examples....119

Schema Creation....119

Updating the Database....120

Update a Local Version of the Database Directly....120

Call a Web Service to Update the Database....121

Checking the Data....122

Web Service....122

Accessing MongoDB....125

The Client....129

Process Data Service....133

Summary....137

Chapter 5: The Admin Application Problem....139

Background....140

Requirements....140

Options....141

Manual Process....141

SOLID....143

Single Responsibility....144

Testability....145

Code Churn....145

Software Resilience....146

A Better Way....146

Open-Closed....147

Inheritance....148

Polymorphism....149

Liskov Substitution....150

Interface Segregation Principle....151

Dependency Inversion Principle....153

Inversion of Control....154

Methods of Extending Software....154

Hooks....155

Messages....156

Mediator....156

Injection....159

Security....159

Target Architecture....161

Examples....163

Basic Functionality....163

Extensibility....168

Custom Functionality....170

Summary....171

Chapter 6: The Travel Rep Problem....173

Background....174

Requirements....174

Options....175

Manual Process....175

Caching....176

Sidecar Pattern....177

Ambassador Pattern....178

Microservices and Containers....180

Target Architecture....180

Containers....181

Examples....182

Project Structure....183

TravelRep.CentralApi....184

Chaos Monkey....185

TravelRep.App....187

TravelRep.Ambassador....188

Hangfire....191

Enqueue and Schedule....193

Persistence and Configuration....193

Hangfire Dashboard....194

Containers....196

Docker Compose....196

Displaying a UI....198

Contacting the Host Machine from a Container....198

host.docker.internal....198

Configuring SSL/TLS....199

mkcert....203

Step 1. Install mkcert....203

Step 2. Install the Trusted Root Certificate....203

Step 3. Create a Certificate....204

Step 4. Copy the Certificate into the Central Service API....206

Step 5. Copy the Certificates to the Ambassador API....207

Durability....209

Summary....210

Appendix A: Technical Appendix....212

Chapter 1....212

Index....217

Design system solutions using modern architectural patterns and practices. This book discusses methods to keep a system responsive, even when it is being constantly updated, extending a system's functionality without changing the core code, methods of maintaining data history, and designing a distributed transactional system.This book will guide you in understanding how a software solution is designed using different architectural processes and scenarios. Each scenario explains if and why a software solution is required to resolve a given issue, and discusses possible architectural approaches to solve the problem. You will learn specific implementations of software architecture for each case along with different approaches to achieve the solutions. Each chapter is structured as a real-world requirement from a client and describes a process to meet that requirement.

After reading this book, you should have a high-level understanding of the architectural patterns used in the book, and you should have a methodology for approaching system design.

What You Will Learn

• Understand design principles and considerations for various stages of software development
• Translate patterns into code samples
• Create a blueprint for approaching system design
• Understand architectural patterns: CQRS, event sourcing, distributed systems, distributed transactions, and plug-in architecture

Who This Book Is For

Developers who wish to move into architecture, and junior software architects also will find the book useful.