Todo List example application

The Todo List application is the hello world application for the Eventuate™ Platform. It illustrates how you can use the platform to write an application with a microservices architecture that uses Event Sourcing and Command Query Responsibility Segregation (CQRS). The Todo List application lets users maintain a todo list.

The Todo List application is a Java and Spring Boot application built using Eventuate™'s Event Sourcing based programming model. Todos are implemented by an Event Sourcing-based TodoAggregate. The aggregate's events are persisted in the Eventuate event store. The application also maintains a materialized view of the data in MySQL.

Don't forget to take a look at the other Eventuate example applications.

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Architecture

The Todo application has a microservice architecture. It is written using the Eventuate Client Framework for Java, which provides an event sourcing based programming model. The following diagram shows the Todo List application architecture:

The application consists of the following:

• Todo service - a Java and Spring Boot-based service that has a HATEOAS-style REST API for creating, updating and querying todo list items. It uses Eventuate to persist aggregates using event sourcing.
• Todo view service - a Java and Spring Boot-based service that provides a REST API for querying todos. It implements a Command Query Responsibility Segregation (CQRS) view of todos using MySQL. MySQL is kept up to date by subscribing to events produced by the Todo service.
• MySQL database - stores the CQRS view of todo list items.

Note: for simplicity, the Todo list application can be deployed as a monolithic application.

Two versions of the source code

There are two versions of the source code:

• single-module - a single module Gradle project for a monolithic version of the application. It is the easiest to get started with.
• multi-module - a multi-module Gradle project for the microservices-based version of the application.

Note: you do not need to install Gradle since it will be downloaded automatically. You just need to have Java 8 installed.

Building and running the application

The steps for building both versions of the application are identical.

Building and running using Eventuate Local

First, build the application

./gradlew assemble -P eventuateDriver=local

Next, launch the services using Docker Compose:

export DOCKER_HOST_IP=...
./gradlew <database-mode>ComposeBuild
./gradlew <database-mode>ComposeUp

Where database-mode is one of:

• mysqlbinlog - use MySQL with Binlog-based event publishing
• postgreswal - use Postgres with Postgres WAL-based event publishing
• postgrespolling - use Postgres with generic JDBC polling-based event publishing

Note: You need to set DOCKER_HOST_IP before running Docker Compose. This must be an IP address or resolvable hostname. It cannot be localhost. See this guide to setting DOCKER_HOST_IP for more information.

Using the application

Once the application has started, you can use the application via the Swagger UI.

If you are running the multi-module version:

• http://${DOCKER_HOST_IP}:8081/swagger-ui.html - the command-side service
• http://${DOCKER_HOST_IP}:8082/swagger-ui.html - the query-side service

If you are running the single-module version:

• http://${DOCKER_HOST_IP}:8080/swagger-ui.html - the monolithic application

Using the Eventuate Local console

You can also use the Eventuate Local console to view aggregates and watch the stream of events. Visit the URL http://${DOCKER_HOST_IP}:8085

Got questions?

Don't hesitate to create an issue or see

• Website
• Mailing list
• Slack. Get invite
• Contact us.