Elastic Applications with Apache Kafka

Sample Implementation

The purpose of this repository is to provide a reference implementation for a sample application that demonstrates the usage of Apache Kafka. The detailed description for the application architecture and the styles underpinning it, please check my blog on Ghost.io

Architectural Styles

The implementation adapts the following architectural styles:

1. Domain Driven Design
2. Command Query Responsibility Segregation
3. Event Sourcing

Technology

The application uses the following set of light-weight technologies and frameworks:

1. Apache Kafka for Messaging
2. MongoDB for Persistence
3. Spring MVC for REST Services
4. Spring Data for Data Access Objects
5. Spring Boot for Bootstrapping and Boilerplates

Prerequisites

Before running the above application, you'll need to install the following on your machine:

1. Maven 3.0.3 or later
2. MongoDB, I used v3.2 at the time of this implementation
3. Apache Kafka v0.9 or later

If you have a Mac OS, you can install the above components using Homebrew. The following commands install the above:

$ brew install maven
$ brew install kafka
$ brew install mongodb

Run

Once you have the above software installed, you can run the application in the following order:

1. Go to the root directory of the application and type: mvn clean install
2. Start the application-api project which is the entry point for REST URL's of the commands. You can start it by navigating to its subdirectory and type: mvn spring-boot:run
3. Start the application project which contains the domain logic and event sourcing. You can start it by navigating to its subdirectory and type: mvn spring-boot:run
4. Start the query-api project which represents the query part subscribing to the published events. You can start it by navigating to its subdirectory and type: mvn spring:boot:run

Variations

The above steps assume the default settings for Mongo and Kafka. If you could like to change any of those settings, please navigate to application.properties file that you'll find under each of the three applications above and then change the proper values and re-run it again.

Interaction

The command part can be tested by POSTing a JSON message to the following REST endpoint: http://localhost:8080/profiles/registrations and the sample JSON request is:

{
    "username": "username",
    "email": "[email protected]",
    "password": "password"
}

As for the query part, you can test it by GET the following REST endpoint: http://localhost:9090/profiles

You can also check the messages as it passes through Kafka using the ./topic-console-consumer utility