January 23, 2017

Kotlin vs Java: An Introduction

Kotlin is a statically typed programming language for the Java Virtual Machine (JVM), Android, and web browsers crafted by the makers of the famous IDE IntelliJ[1]

The Willhaben Android App relies on traditional Java code and a growing amount of Kotlin code. Right now, we are in a transition period of migrating our legacy Java code to Kotlin. As Java and Kotlin both work on the JVM, they can be used in conjunction within the same codebase.

During my work with Kotlin, I stumbled upon some pretty interesting language details and features, some of which I want to explain briefly in the next few lines and in an upcoming blog post. I’ll also give you a comparison of how the same results can be achieved in the Java world. In this post, I will focus on two features.

January 18, 2017

Building a 144 core Raspberry PI 3 Cluster

A couple of months ago, we built a cluster of 36 Raspberry PI 3 (4 cores each, so 144 cores in total), resulting in 2304 GB of storage and 36 GB of RAM. There are many tutorials about building small Raspberry PI clusters available online, but hardly any of them cover what you can do with them in a business environment. So, why did we spend a lot of time to get this thing to work?

144 Core Raspberry PI 3 Cluster
First, our cluster is like a data center in a box. It just has a network cable and a power cable, so it actually is “plug and play.” Everything else is contained in the cluster shown in the picture. We had to build the hardware, the electronics, and to create the networking, routing, etc. We asked a team of software engineers and operations specialists to work closely together on this project. Participating in a project like this gives each of the members insight into other areas that are usually not part of their daily work; software guys learned more about networking and how to set up the proper administration of servers, and operations guys learned more about the software side.

January 02, 2017

How to integrate Docker into your build process

In this blog post I want to show you how to install Docker on your system and integrate it into your build process. So that it will be easy for you to run your tests against a running Docker container, we will add a Postgres database to the Docker container. This will enable you to test them against a fresh and clean database every time you run tests.

Docker Installation

For general installation instructions you can visit the Docker homepage and follow the steps there. In my example I will install it on a computer running Linux Mint, which is a derivative of Ubuntu, so you can follow the Ubuntu installation steps.