Lightbend Activator

Reactive DDD with Akka

Activator will be EOL-ed on May 24, 2017.

We’re making it easier and simpler for developers to get started with Lightbend technologies. This unfortunately means that future releases of Play, Akka and Scala will no longer include Activator support, and Lightbend’s Activator server will be decommissioned by the end of 2017. Instead of supporting Activator to create and set up development projects, we'll be supporting standard Giter8 templates for sbt users and Maven archetypes for Maven users. So going forward,

To create new Lightbend projects

Instead of using the Activator command, make sure you have sbt 0.13.13 (or higher), and use the “sbt new” command, providing the name of the template. For example, “$ sbt new akka/hello-akka.g8”. You can find a list of templates here.

Also, as a convenience, the Lightbend Project Starter allows you to quickly create a variety of example projects that you just unzip and run.

To create new templates

If you want to create new templates, you can now do that in Giter8.

To migrate templates from Activator to Giter8

If you created Activator templates in the past, please consider migrating them to Giter8 with this simple process.

Reactive DDD with Akka

Paweł Kaczor
Source
January 3, 2018
akka akka-persistence cluster-sharding cluster cqrs event-sourced scala

Sample e-commerce application built on top of Akka and EventStore following CQRS/DDDD principles.

How to get "Reactive DDD with Akka" on your computer

There are several ways to get this template.

Option 1: Choose ddd-leaven-akka in the Lightbend Activator UI.

Already have Lightbend Activator (get it here)? Launch the UI then search for ddd-leaven-akka in the list of templates.

Option 2: Download the ddd-leaven-akka project as a zip archive

If you haven't installed Activator, you can get the code by downloading the template bundle for ddd-leaven-akka.

  1. Download the Template Bundle for "Reactive DDD with Akka"
  2. Extract the downloaded zip file to your system
  3. The bundle includes a small bootstrap script that can start Activator. To start Lightbend Activator's UI:

    In your File Explorer, navigate into the directory that the template was extracted to, right-click on the file named "activator.bat", then select "Open", and if prompted with a warning, click to continue:

    Or from a command line:

     C:\Users\typesafe\ddd-leaven-akka> activator ui 
    This will start Lightbend Activator and open this template in your browser.

Option 3: Create a ddd-leaven-akka project from the command line

If you have Lightbend Activator, use its command line mode to create a new project from this template. Type activator new PROJECTNAME ddd-leaven-akka on the command line.

Option 4: View the template source

The creator of this template maintains it at https://github.com/pawelkaczor/ddd-leaven-akka-v2.

Option 5: Preview the tutorial below

We've included the text of this template's tutorial below, but it may work better if you view it inside Activator on your computer. Activator tutorials are often designed to be interactive.

Preview the tutorial

ddd-leaven-akka-v2

Reactive DDD with Akka

Overview

This sample e-commerce system has unique set of properties. It is:

  • responsive, resilient, elastic,
  • incorporates a SOA, EDA, and Microservice architecture,
  • incorporates CQRS/DDDD architectural patterns,
  • supporting long-running business processes (eg. payment deadlines), and
  • developer-friendly (implemented in Scala, ~1500 lines of code).

All these capabilities are obviously supported by the underlying technology stack, which includes:

  • Akka - actor-based, reactive middleware implemented in Scala,

  • Akka HTTP - HTTP server build upon Akka Stream (Akka's implementation of Reactive Streams Specification),

  • Akka Persistence - infrastructure for building durable (event sourced) actors, which has a pluggable journal,

  • Event Store - scalable, highly available event store with akka-persistence journal implementation. Provides engine for running user-defined projections (javascript functions) over single or multiple event streams. Projections allow the system to group or combine events into new event streams that can represent domain-level journals such as office journals (events grouped by emitter (Aggregate Root) class) or business process journals (events related to concrete business process). Domain journals are topic of interest for services such as:

    • view updaters - responsible for updating the read side of the system
    • receptors - allow event-driven interaction between subsystems (event choreography), including long-running processes (sagas), and
  • Both view uppdaters and receptors are operating within non-blocking back-pressured event processing pipeline

  • Akka-DDD - framework containing glue-code and all building blocks

Subsystems

The system currently consists of the following subsystems:

  • Sales/Reservation - responsible for creating and confirming Reservations
  • Invoicing - responsible for the invoicing
  • Shipping - responsible for the goods delivery
  • Headquarters - executes the Ordering Process (see below)

Ordering Process

Applications

Each subsystem is divided into write and read side, each side containing back-end and front-end application:

write-back

Backend cluster node hosting Aggregate Roots, Receptors and Process Managers (Sagas).

write-front

HTTP server forwarding commands to backend cluster.

read-back

View update service that consumes events from event store and updates view store (PostgreSQL database).

read-front

HTTP server providing rest endpoint for accessing view store.