in microservices using ddd, event sourcing & cqrs · java, android javascript native. 2. kotlin...

in Microservices using DDD, Event Sourcing & CQRS

Augusto BranquinhoMike Shigueru Matsumoto

Technical stack

1. Real Wave

Modules

Information

Frontend

Integration

Backend

Marketing

Sales

Care

Payments

Insights

Integration

2. Kotlin

Designed by Jetbrains

Kotlin in production: Google, Pivotal, Uber, Atlassian, Coursera, etc

Statically typed

Modern

Drastically reduce the boilerplate

Java, Android

Javascript

Native

https://www.jetbrains.com

2. Kotlin

Data Class

toString

equals

hashCode

copy

properties - get/set

2. Kotlin

🤢 Java

😎 Kotlin

Lambda

2. Kotlin

Higher Order Functions

2. Kotlin

Extension method

Reified & Inline

2. Kotlin

Smart cast

Pattern matching

String template

Reified

Operator overloading

Unit and Nothing

High order function

Infix

Internal

Properties

Extension methods/properties

Lazy initialization, Delegation

Object (singleton)

Deprecated

Default value

Tacit programming: let, also, apply, run, with

Tailrec

…

3. Event Sourcing & CQRS

Event Sourcing (ES)

100% reliable logging (aka: version control)

all operations on the system are stream event-oriented: nothing happens before the event being committed

it is possible to rebuild all the views since the beginning of time

you can build new views using the same principle

events are immutable


CQRS

"It's a pattern" (Greg Young)

uses a different model to update (Command) and another to read (Query)

Command (accept/reject)Change stateEvents

Query (views)Are free of side effects


MotivationES, CQRS

Clients: Bank, TelecomAudit Log (query the past)InsightsMultiple views (Multi-Tenant)

E.g.: Catalog managerReliable logsOffers are immutableHigh requests rate (millions)Decoupled views


Real Wave Microservices

Command Api

Catalog Manager

Query Api

Catalog Search

Join Use Pay

query response

Catalog Processor

accept/reject

Offers


Catalog Search

Catalog Processor

Low write latency

High read latency

Catalog Manager


Code

Command Bus


DDD

Command Bus


❌✔Bounded Context


Command Bus

First Command

Nothing was replayed yet


DDD


Happens in the past

Just accept, no logic here


Command Bus ❌❌Not here yet!!!


Command Bus

Replay for all past events will start for this ID before this Command executes⚠


1 - Replay


2 - Accepts/Rejects

1 - Replay


3 - Accepted

1 - Replay

2 - Accepts/Rejects


Catalog Processor

Another team maybe?🤔


Catalog Search

Micro Services


A

B

CD

E

F Catalog Search

Catalog 1Catalog 2

Catalog 3Catalog n


😌Conclusion


🔥Burn down

Conclusion😌


🏗Replay

TODOsnapshotssagas

recoveryfix inconsistencybuild a new view

😌Conclusion

Motivation

KotlinEvents (immutable) (Axon)

Catalog v1Data class (boilerplate)Event Stream

lambdaModernEasy to learn…

4. Kotlin, DDD, ES & CQRS

Why should you try using Kotlin?



Events (Event Store Database)Smart Casts

Pattern Matching

Final

Sealed Class


Events (Event Store Database)


Value Objects - data classTypesafe

Primitive ObsessionInvalid ObjectsImmutability


Anemic Domain Model - kotlin extensionsOnly Getters / SettersServices Layers are OVER ABUSED!!!

😎

😖

5. Kotlin 102

Tests

5. Kotlin 102

Coroutines

asynchronous programming

we put the complications into libraries

experimental != unsecurity

5. Kotlin 102

Coroutines

What's the result?

5. Kotlin 102

Coroutines are light weight! 😱

5. Kotlin 102

Coroutines are light weight!

😱

😱

Coroutines - async/await

5. Kotlin 102

5. Kotlin 102

Kotlin is the path to Functional Programming. Functional Programming leads to Pure Functions, Pure Functions leads to Monad and Asynchronous Programming. Asynchronous Programming leads to Reactive Programming.

Master Yoda - Return of the Jedi

5. Kotlin 102

Functional ProgrammingPurity (no-side effect) Purity vs I/O

Exceptions propagationThread limits

Referential Transparency

5. Kotlin 102Monad/Either - zkotlinhttps://github.com/ZupIT/zkotlin

https://github.com/ZupIT/zkotlin

5. Kotlin 102Monad - Either -> Either -> Either

FOLD HELL

5. Kotlin 102

Either foldCompose

5. Kotlin 102

Either foldCompose ping-pong effectE.g. Payments Retry

😞

5. Kotlin 102

Either foldCompose ping-pong effect

😇

5. Kotlin 102

Either foldCompose ping-pong effect

😎

5. Kotlin 102

Either, Coroutines, Extensions, zkotlin all together

5. Kotlin 102

Wraps I/O problems with Either<L,R>

5. Kotlin 102

Wraps I/O problems with Either<L,R>

✔

❌

❌

Remote I/O

5. Kotlin 102

sync {}

async {}

5. Kotlin 102runBlocking

5. Kotlin 102zkotlin

Couroutines/Ext. Methods

5. Kotlin 102Conclusion

Kotlin & Functional ProgrammingPurity, Referential Transparency, Immutability

Higher-order functionsSugar syntax (it, ƛ as last parameter)

Less boilerplatea nicer syntax to compose Either pattern

Coroutines is easy to use

Ready for Spring Reactor

Catalog Reindex Process before Coroutines: +/- 30 m, after < 4 m

😌

Everything is final on Kotlin

6. Kotlin, Java & Legacy

Spock Mockito

SpringBoot - allopen


final


JPA


Spring Data QueryDSL - Plugins (modules)

Default Interface Java 8 (Kotlin 1.2.40)

Lambdas return - Unit

Mike Shigueru MatsumotoEmail: [email protected]

Augusto BranquinhoEmail: [email protected]

Conclusion

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