Practical Microservices: Build Event-Driven Architectures With Event Sourcing and CQRS

Cover
Table of Contents
Acknowledgments
Introduction
	Telling a Tale of a Different Kind of Keyboard
	What This Book Is
	What This Book Isn’t
	Separating Principles from Implementations
	Using This Book
	Using Node.js
	Strapping In
Part I—Fundamentals
	1. You Have a New Project
		Kicking Off Video Tutorials
		Building the Bones
		Mounting Middleware
		Injecting Dependencies
		Taking the Server for a Spin and Starting the Database
		Serving the Home Page
		Connecting the Home Page Application
		Mounting the Home Application into Express
		Building the Record Views Application
		Recording State Changes
		Charting a New Course
		What You’ve Done So Far
	2. Writing Messages
		Unmasking the Monolith
		Trying to Compress Water
		Extracting “Microservices”
		Defining Services
		Getting Components to Do Things
		Representing Messages in Code
		Naming Messages
		Storing State as Events
		Storing Messages in Streams
		Defining Component Boundaries
		Recording Video Views
		Writing Your First Message
		(Re)configuring the Record-Viewings Application
		Hanging a Lantern
		What You’ve Done So Far
	3. Putting Data in a Message Store
		Defining Requirements
		Fleshing Out Message Structure
		Surveying Message DB
		Scaffolding the Message Store Code
		Connecting to Message DB
		Writing write
		Adding Optimistic Concurrency Control to Our Writes
		“Can’t Kafka Do All of This?”
		What You’ve Done So Far
	4. Projecting Data into Useful Shapes
		Handling Events
		(Re)Introducing the RDBMS
		Writing Your First Aggregator
		Handling Asynchronous Messages
		Getting Idempotent with It
		Connecting to the Live Message Flow
		Configuring the Aggregator
		Having the Home Page Application Use the New View Data
		Coming to Terms with Data Duplication
		What You’ve Done So Far
	5. Subscribing to the Message Store
		Sketching the Subscription Process
		Managing the Current Read Position
		Fetching and Processing Batches of Messages
		Orchestrating the Subscription
		Reading the Last Message in a Stream
		Reading a Stream’s Messages
		Adding the Read Functions to the Message Store’s Interface
		Starting the Server
		What You’ve Done So Far
Part II—Fleshing Out the System
	6. Registering Users
		Discovering Domain Messages
		Starting with the Business Process
		Translating the Business Processes into Events and Commands
		Fleshing Out the Identity Messages
		Examples from Other Domains
		Adding Registration to Our System
		Turning Registration Requests into Commands
		Superficially Validating User Input
		Ensuring Uniqueness of Email Addresses
		Finishing the Application
		Validating Eventually Consistent Data
		Coping with Trade-Offs
		What You’ve Done So Far
	7. Implementing Your First Component
		Fetching a Stream’s Current State
		Joining the “I Wrote a Microservice” Club
		Wiring the Identity Component into the System
		Disambiguating “Projections” and “Replaying”
		Taking It Further
		What You’ve Done So Far
	8. Authenticating Users
		Aggregating Registered Events
		Discovering the Authentication Events and Commands
		Letting Users in the Door
		Using Third-Party Authentication
		What You’ve Done So Far
	9. Adding an Email Component
		Discovering the Email Component Messages
		Addressing Idempotence
		Adding the Component
		Sending the Email
		Running the Component
		Adding Email to the Registration Process
		Recording Registration Emails
		Making the Message Store Aware of Origin Streams
		Revisiting Idempotence
		Orchestrating Components vs. Choreographing Components
		What You’ve Done So Far
	10. Performing Background Jobs with Microservices
		Accidental Complexity
		Use Case #1: Sending Emails
		Use Case #2: Transcoding Videos
		Describing the Creators Portal
		Aggregating Is Also for Other Teams
		Building the Video Publishing Component
		Accepting Potential Duplication
		What You’ve Done So Far
	11. Building Async-Aware User Interfaces
		Defining Video Metadata Messages
		Responding to Users When the Response Isn’t Immediately Available
		Adding Validation to a Component
		Aggregating Naming Results
		Applying Naming Events to the Creators Portal View Data
		Justifying Our UI Decision
		What You’ve Done So Far
Part III—Tools of the Trade
	12. Deploying Components
		Creating the Heroku “App”
		Configuring the “App”
		Installing Message DB
		Deploying the System
		Distributing the System
		Deploying Databases
		What You’ve Done So Far
	13. Debugging Components
		Priming the Database with Example Data
		Introducing the Admin Portal
		Creating Users
		Wiring the Users View into the Admin Portal
		Hooking the Admin Portal into the Rest of the System
		Inspecting the Results So Far
		Thinking Through the Expected Flow
		Correlators Gonna…Correlate?
		Imagining Our Way to Good System Monitoring
		Starting from the Beginning
		Viewing Messages by Stream
		Augmenting the Message Store for $any and $all
		What You’ve Done So Far
	14. Testing in a Microservices Architecture
		Revisiting the Fundamentals
		Writing Tests for Autonomous Components
		Writing Tests for Message-Writing Applications
		Keeping It Simple
		Dropping Testing?
		What You’ve Done So Far
	15. Continuing the Journey
		Handling Concurrency
		Snapshotting
		Changing the Message Contract
		Using Different Programming Languages
		Making Use of Monoliths
		What You’ve Done So Far
A1. ES6 Syntax
	const and let
	Arrow Functions
	Object Destructuring
	Object Literal Property Value Shorthand
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