io.github.crabzilla:crabzilla-kotlin-example1

Yet another Event Sourcing experiment

License	MIT License
Categories	Kotlin Languages
GroupId	io.github.crabzilla
ArtifactId	crabzilla-kotlin-example1
Last Version	0.0.5
Release Date	Aug 21, 2017
Type	pom
Description	Yet another Event Sourcing experiment

Download crabzilla-kotlin-example1

Filename	Size
crabzilla-kotlin-example1-0.0.5.pom	2 KB

How to add to project

Apache Maven

<!-- https://jarcasting.com/artifacts/io.github.crabzilla/crabzilla-kotlin-example1/ -->
<dependency>
    <groupId>io.github.crabzilla</groupId>
    <artifactId>crabzilla-kotlin-example1</artifactId>
    <version>0.0.5</version>
    <type>pom</type>
</dependency>

Gradle Groovy

// https://jarcasting.com/artifacts/io.github.crabzilla/crabzilla-kotlin-example1/
implementation 'io.github.crabzilla:crabzilla-kotlin-example1:0.0.5'

Gradle Kotlin

// https://jarcasting.com/artifacts/io.github.crabzilla/crabzilla-kotlin-example1/
implementation ("io.github.crabzilla:crabzilla-kotlin-example1:0.0.5")

Apache Buildr

'io.github.crabzilla:crabzilla-kotlin-example1:pom:0.0.5'

Apache Ivy

<dependency org="io.github.crabzilla" name="crabzilla-kotlin-example1" rev="0.0.5">
  <artifact name="crabzilla-kotlin-example1" type="pom" />
</dependency>

Groovy Grape

@Grapes(
@Grab(group='io.github.crabzilla', module='crabzilla-kotlin-example1', version='0.0.5')
)

Scala SBT

libraryDependencies += "io.github.crabzilla" % "crabzilla-kotlin-example1" % "0.0.5"

Leiningen

[io.github.crabzilla/crabzilla-kotlin-example1 "0.0.5"]

Dependencies

compile (2)

Group / Artifact	Type	Version
javax.inject : javax.inject	jar	1
org.slf4j : slf4j-api	jar	1.7.8

provided (1)

Group / Artifact	Type	Version
org.projectlombok : lombok	jar	1.16.18

test (4)

Group / Artifact	Type	Version
org.junit.vintage : junit-vintage-engine	jar	4.12.0-RC2
org.junit.jupiter : junit-jupiter-api	jar	5.0.0-RC2
org.mockito : mockito-core	jar	2.7.4
org.assertj : assertj-core	jar	3.5.0

Project Modules

• crabzilla-kotlin-example1-core
• crabzilla-kotlin-example1-database
• crabzilla-kotlin-example1-service

crabzilla

Update: February 2021

After many months, I'm back active working on this project. I just got a job working with Kotlin so I'm motivated again. These are some plans:

• Dependencies upgrade (Vert.x, Kotlin, etc)
• Refactor unit of work table: splitting it into 2 tables: 1 for events and another for commands - The current model doesn't have a true event store. Also: the events table will have only one event per row instead of a json with N events given a command. The command table will have reference to the respective events. This will allow to correct events within the event store.
• I will keep with Kotlin Serialization but still wondering about an approach I've used before: https://einarwh.wordpress.com/2020/05/08/on-the-complexity-of-json-serialization/
• I will avoid trying integrations with RabbitMq, Hazelcast, etc like I did before: it isn't within the scope of Crabzilla.
• I will rewrite Accounts example app with Quarkus (I'm just waiting Quarkus to reach Vertx 4
• May be the adoption of some parts of https://arrow-kt.io/ Using optics instead of plain Kotlin copy for aggregates, for example.

Goal for version 1.0.0

To help writing CQRS and Event Sourcing applications with Vert.x

Status

It's still in very early development stage. Do not use release 0.0.5, master branch is very different from that.

Example

• Accounts Example

Building

Requirements

• Java 8
• Maven (tested with 3.5.0+)
• Docker compose (tested with 1.18.0)
• Kotlin plugin for your IDE

Steps

1. Clone it:

git clone https://github.com/crabzilla/crabzilla
cd crabzilla

2. Start docker-compose running a Postgres database (port 5432 will be used):

docker-compose up

3. Open another terminal and build it, running both unit and integration tests:

mvn clean install -DskipTests=false

Random notes

1. Crabzilla tries to provide a chassis for wiring and running your domain by using plain verticles.
2. If your command handling functions are pure, all side effects will occurs within:
   • core.UnitOfWorkJournal: to save the events to a database using optimistic concurrency control
   • pgc.PgcUnitOfWorkProjector: to project events to a read model using a PostgreSql database using vertx-pg-client
   • jooq.JooqUowProjector: to project events to a read model using vertx-jooq-classic-reactive
3. So far events from all entities are written as an UnitOfWork in Json format into a single partitioned append only table.

Versions

Version
0.0.5 Aug 21, 2017