This sample code helps get you started with a CQRS + Event Sourcing Patterns

To know about CQRS: https://martinfowler.com/bliki/CQRS.html

To know about Event Sourcing: https://martinfowler.com/eaaDev/EventSourcing.html

Related technologies:

• Kotlin: https://kotlinlang.org/docs/reference/
• Spring Boot: https://spring.io/projects/spring-boot#overview
• Axon Framework: https://axoniq.io/resources/architectural-concepts
• Docker: https://www.docker.com/resources/what-container
• Apache Kafka: https://kafka.apache.org/intro
• Zookeeper: https://zookeeper.apache.org/
• MongoDB: https://www.mongodb.com/what-is-mongodb

This sample includes:

• branch master - Normal spring boot application with servlet container.

• branch webflux (In progress) - Spring Boot Webflux with Netty server, more functional style (See https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html for details).

• branch distributed-command - This branch uses Netflix Eureka to distribute commands.

• README.md - this file

• docker-compose.yml - this file is used by Docker Compose (https://docs.docker.com/compose/) to running Kafka, Zookeeper and Mongo

• pom.xml - this file is the Maven Project Object Model for the web service

• command-server - this directory contains your Kotlin Service Command source files

• query-server - this directory contains your Kotlin Service Query source files

• sample-core - this directory contains the shared source code between modules, command-server and query-server

• service-discovery (branch distributed-command) - this directory contains your Service Discovery (Eureka) to enable distributed commands

To work on the sample code, you'll need to clone project's repository to your local computer. If you haven't, do that first.

1. Install maven. See https://maven.apache.org/install.html for details.

2. Install Docker (to run Kafka, Zookeeper and Mongo). See https://docs.docker.com/install/

3. Build the services.

    $ cd sample-cqrs
    $ mvn clean install
   

4. Run the Docker Compose.

    $ docker-compose up -d
   

5. Run the Eureka (if distributed-command branch)

    $ cd service-discovery 
    $ mvn spring-boot:run 
   

6. Run the Command Server

    $ cd command-server
    $ mvn spring-boot:run 
   

7. Run the Query Server

    $ cd query-server
    $ mvn spring-boot:run 
   

8. Send Command to create the sample data

   action types:

     CREATE
            
     CREATE_AND_CANCEL 
   

   The action (CREATE_AND_CANCEL) rollback status to CANCELED using Saga Pattern

    $ curl -v -X PUT \
        http://localhost:8084/command-sample/api/samples \
        -H 'Content-Type: application/json' \
        -d '{
        "id": 1234,
        "stuff": "Lorem Ipsum",
        "action": "CREATE"
      }'
   

9. Call the Query endpoint

    $ curl -v -X GET http://localhost:8085/query-sample/api/samples/1234