The domino tutorial

Purpose

This tutorial offers a way to learn Kotlin language, Neo4J graphDB and many other stuffs by following the development of a real project: domino.

Description of the domino project

The domino project is a processing manager. Its purpose is:

• gives a way to build a processing tree by connecting tasks
• launches processing in parallel
• manages errors and retries

Why is project named domino?

How do we manage a processing ? We run the first task and when it's done, we run the second one. Each task result leads to another until the last one. Sometimes, the end of a task leads to launch two or more tasks in parallel and other times a task waits for the result of many previous tasks. Take a look here.

Technical

Currently, the domino project is built on:

• Kotlin (a JVM language) http://kotlinlang.org/
• Neo4J graph database http://neo4j.com/
• Linux or OS X OS
• Bash scripts or Python

About the choice of the Neo4J database

The Neo4J database has been chosen because of:

• very good integration in JVM environment
• the Cypher query language
• the existence of a community edition of the database
• Isn't the best choice to save a tree representation into a graph DB ?
• Changes in the model are fast and easy.

About the choice of the Kotlin language

The main language is Kotlin because:

• It's well thought
• It offers some capabilities from dynamic languages like Python or Groovy while being a static language
• High-order functions
• Its null-safety system
• It's a JVM language (good integration with Java language and Java tools)

Domain Driven Design

The domino project will be developed following the domain driven design (https://en.wikipedia.org/wiki/Domain-driven_design). Often, use the domain driven design has an important time cost because changes are not easy with relational database. But this cost is reduced thanks to usage of Neo4J DB.

Who is behind the domino project?

I'm a French software architect and developer for more 15 years. I started with C/C++ and now I often develop with JVM languages as Java8 or Kotlin and I tried others as Groovy, Clojure. I like the functional paradigm (I discovered it with Clojure and Haskell) and I try to find the best compromise between functional and object programming. For me, nothing is bad: we have to use the best tool for a problem.

So?

Theses pages below will be update all along the development of this project.

1. What do we want domino to make ?
2. Entities definition
3. First development step: template management