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Publications

Testing Spark Streaming: Integration testing with Docker Compose

In the first post of this series, we saw how to unit test Spark Streaming operations using Spark Testing Base. Here we'll see how to do integration testing using Docker Compose. What is Integration testing We previously saw a discussion about unit and integration testing....


Testing Spark Streaming: Unit testing

There is enough evidence to prove the importance of automated testing. Projects in new fields often neglect automated testing, as the domain itself steals the attention of the developers. However, lack of testing implies 'laugh now, cry later'. Some of the tools around Big Data...


State in scalable architectures

Handling state is one of the cornerstones of software development. Most of business value derived from software relies on state. Depending on the level of abstraction, state, and the approach to handle it, looks like a completely different problem. In this post we'll see what...


Unit vs Integration Akka Testing

This is the sixth post in the series about integrating sync clients with async systems (1, 2, 3, 4, 5). Here we'll see how to test Akka actors with different testing styles. Unit vs Integration Testing Nowadays everybody agrees with the famous testing pyramid: Harder...


Coordination in Akka

This is the fifth post in the series about integrating sync clients with async systems (1, 2, 3, 4). Here we'll see how to manage the actor's lifecycle, so our service can use the available resources efficiently. Lifecycle Actors, threads, objects, resources... All of them...


Publish-subscribe model in Kafka

This is the fourth post in the series about integrating sync clients with async systems (1, 2, 3). Here we'll try to understand how Kafka works in order to correctly leverage its publish-subscribe implementation. Kafka concepts According to the official documentation: Kafka is a distributed,...


Finite state machines with Akka

As you could remember from previous posts, Part 1 and Part 2, we're implementing a solution that integrates a sync client with an async system. Today we'll see how to keep track of the async operations so we can provide a sync response to the...


Akka basics

As the previous post explained our system is based on Akka. Before going into more detail about our solution, I'd like to explain what Akka is about and why it is so awesome. Akka is a toolkit and not a framework, you can simply use...


Async systems with sync clients

As the Reactive Manifesto says Reactive systems are: Responsive Resilient Elastic Message Driven The last principle often goes together with non-blocking async protocols. This style of communication "allows recipients to only consume resources while staying active, leading to less system overhead". This fits perfectly with...


Sorted pagination in Cassandra

Cassandra is a fantastic database for different use cases. There are different situations when you need to twist Cassandra a little and studying one of those could be a helpful exercise to better understand what is Cassandra about. Databases are complex beasts, approaching them with...


Coupling in distributed systems

Coupling and cohesion are key quality indicators. We strive for systems highly cohesive and loosely coupled, but high doesn't mean pure. The same goes with functional programming, we aim for isolating and reducing side effects, but we need them unless we want a useless system....


Testing multithreaded code in Java

Testing multithreaded code is a tough challenge. The first advice that you get when trying to test concurrency is to isolate your concurrent concerns in the code as much as possible. This a general design advice but in this case it's even more important. Make...


Tips for a friendly open source experience

Open source has moved from being an important actor in software development to being central for plenty of people, especially thanks to Github. Most of us are simple users of OSS (Open-source software) but being brave and taking a step forward and becoming a contributor,...


Transcending REST and RPC

It seems that a new paradigm is coming. Facebook and Netflix have come up with different implementations for that idea. Some people are calling it Demand-Driven Architecture, but before I show you some solutions, let's go over some history to understand the problem. I will...


CQRS and Event Sourcing for dummies

CQRS (Command and Query Responsibility Segregation) and Event Sourcing are concepts that are not new at all. Alongside NoSql, Functional Programming and Microservices, these revival concepts are getting traction because of their ability to deal with modern software challenges. Assuming that you're building a product...


Side effects and Java 8 streams

There is a lot of excitement in the Java community since Java 8 was released. Lambdas and Streams are a massive improvement and nobody wants to go back to the old days. Today, however, I want to talk about the caveats of some use of...


Dangerous Words

Ludwig Wittgenstein was one the greatest philosophers of 20th century. His book Tractatus Logico-Philosophicus addresses the limits of language and its relationship with reality. A friend of mine, great polemicist, suggested me to read it some years ago to understand one of his favourites conversational...