Luiz Kowalski :: dev blog

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Luiz Kowalski

Taming complex Service Objects with dry-rb

As your Rails app grows, MVC feels inadequate. Should I put complex business rules in the models or in the controllers? Should I just put everything in concerns? At this point, most developers fall back to good'ol Service Objects: specialized classes with a single goal (register a user, send an

Using concurrent-ruby in a Rails application

Concurrency in Ruby is still a gray zone for many developers. If you know anything about concurrency, you probably know that Ruby is thread-safe by default because the Global VM Lock only uses one thread and you are bounded by it. But does that mean that Ruby can't scale? GVL

Validating Mandrill webhook signature on Ruby on Rails

I'm writing this post partially because I couldn't find anything exactly like this and to keep a log for me, in case I have to deal with this once again. Since Mandrill does not provide a way to authenticate their webhooks using, for example, a user/password combination, they came

Encapsulation in Ruby on Rails

In Object-Oriented Programming, encapsulation is one of the fundamentals concept. Understand encapsulation will help you write concise and easy to maintain code. But what exactly is encapsulation? If you search on the Internet you might find something like this: encapsulation is hide the internal representation or state of an object.

A simple solution to scalability problems: Event Sourcing

In the past months I've been playing around with Kotlin and Spring's event sourcing engine. To get to know it better, I build a really simple clone of Untappd. If you don't know Untappd, a tl;dr is: Foursquare for beers. You can checkin a beer, share it, rate the

Deploying Spring Cloud Netflix apps on Kubernetes

If you are deploying containers on production, Kubernetes is a no-brainer solution. It takes some time to get familiar with all concepts but once you understand it, piece of cake 🍰. So today I wanna show you how to deploy an Eureka server, a Hystrix dashboard with Turbine and a microservice.

Refactoring legacy Ruby on Rails apps

I have this idea: Chathub, an app that turns Github's organizations and/or repositories into chat rooms, pretty much like Gitter. I use this idea every time I want to build a new PoC. So I did it in Rails, in Java when I wanted to go deeper into Spring

Netflix OSS: A beginner's guide [pt4]

When a system grows, you need some kind of monitoring as well. If you have a monolithic app, that is not really a hard task, but when it comes to microservices word, things change. How to keep track of hundreds of instances? How do you know if one of them

Netflix OSS: A beginner's guide [pt3]

So far, we created an Eureka server, a microservice and registered it in Eureka. You can access this microservice directly through his IP, but later, when you service grow and you need to scale it, probably you'll want to load balance between two or more instances. So of course Spring

Netflix OSS: A beginner's guide [pt2]

In the last post, I showed how to create a Eureka server. Now we'll go through the process of creating microservice and register it on Eureka. To begin, you can create a simple project with one entity, for example, a contact list. I will not spend time on the process