Welcome to our second article about Keycloak Server! Previously, we’ve learnt to setup the server and make use of it in a webapp – today, we’re going to create a matching backend API and also learn a little bit about the OAuth2/OpenID magic that powers our entire authn/authz mechanism. Let’s get started! Read more


In this article, we will take a closer look at the core of Akka in an attempt to improve its overall performance.

To begin with, we will provide a short overview of the Akka toolkit and the Actor system. Following that we will study the life cycle of a message in order to gain a better understanding of what makes the Akka’s actor implementation tick. We will continue with a brief review of one of the common types of Executor Services that are used in Akka, while exposing its implementation details. Read more

In this post I will try to present what is GraphStage in Akka Streams. My goal is to describe when it’s useful and how to use it correctly. I will start with outlining key terminology, then proceed with simple example and after that the main use case will be covered. For the latter the most upvoted issue of akka-http will serve.

At the end, I will show how to properly test GraphStage. Besides of learning API you’ll gain deeper understanding how backpressure works. Read more

A very common scenario in many kinds of software is when the input data is potentially unlimited and it can appear at arbitrary intervals. The common way of handling such cases is using the Observer pattern in it’s imperative form – callbacks.

But this approach creates what’s commonly called “Callback Hell”. It’s a concept basically identical to the more commonly known “GOTO Hell” as they both mean erratic jumps in flow of control that can be very hard to reason about and work with. When writing an application we need to analyze all the callbacks to be sure e.g. we’re not using a value that can be changed by a callback at a random point of time.

But there exists a declarative approach to solving this problem that let’s us reason about it in a much more predictable and less chaotic fashion – Streams. Read more

When operating an Akka cluster the developer must consider how to handle network partitions (Split Brain scenarios) and machine crashes. There are multiple strategies to handle such erratic behavior and, after a deeper explanation of the problem we are facing, I will try to present them along with their pros and cons using the Split Brain Resolver in Akka, which is a part of the Reactive Platform. Read more

If you’re looking for the best library to build concurrent and distributed applications, probably sooner than later you’ll come across Akka. It’s a very powerful open source library maintained by Typesafe for making such apps. Read more

Akka Streams is an exciting new technology from Typesafe that is an implementation of the Reactive Streams specification. To this point two other implementations have been declared (from the Reactor team and Netflix’s RxJava team) but only the Typesafe’s implementation is mature enough to do some experimenting with it. This blog covers the 0.3 version of Akka Streams. You can find the API here

RabbitMQ is a messaging broker implementing AMQP 0-9-1 protocol. It’s known for its reliability, speed and simplicity in everyday use.

These two technologies seem like a perfect fit, so in this post I’m going to explore some basic integration possibilities and example usage. Read more