Not all docker images are available for ARM architecture (hopefully this will improve over time). Right now I’m working on a project where images for ARM are not available. Emulation works ok (but slow) most of the time. Lately, I stumbled upon an interesting performance/startup issue when running a...

I have two GitLab accounts - "work account" and "personal account". One is for my professional work, it is registered to my work email. The second account is for my private/learning projects registered with my private email address. I want to keep those things separate and use two different identiti...

Using Gson in your e2e tests might result in tests passing even when contract is broken. Gson is quite imprecise when it comes to deserializing objects from json. Is there any difference between an enum and a string? Is there any difference between s string and a number? Using Java you might answer:...

The circuit breaker is a communication pattern that helps to avoid cascading failure of the system and gives dependent services time to recover. Along with fallback values defined by the developer, it gives a pretty wide safe net when communication channel is broken. Read more

Real-life OpenAPI specification files tend to go really big really fast. In this post, I’ll try to explore how we can split single specification file into multiple files and don’t get crazy while scrolling up and down like a mad man. Read more

Collections are an important part of every programming language. In python, there is a couple of built-in collections like list, set, dictionary but I’m not going to dig into them now. In this post, I’ll explore what it takes to implement collection like objects on your own using collections protoco...

Working with python is fun (as with any language you get hooked up on). You can write simple scripts with it, or complex programs and utilities. The most surprising thing for people coming from the java world might be that in this "scripting" language everything is an object. In this post, I’ll expl...

The simplest possible strategy that can help with communication issues is retrying to execute the request again. Maybe it was just a network glitch and it will work just fine when you try to call it again. Introducing retries is a relatively simple step that can improve the stability of your service...

At work, we are splitting the monolithic application into smaller services. From time to time we have some challenges in doing it the right way. Lately, most of the splitting is focused on cutting out frontends to be outside of the monolith. It gives solid results as we are getting logic and busines...

In this post, I’d like to show you how I’ve started with writing this blog. How the process evolved during 3 years of writing. How I’ve finally managed to set up everything in a way that works for me now. If you don’t blog yet this might help you out with technical details on how you can start easil...

When I’ve first learned that there is something more than printing things to console log4j was state of the art solution. Then SLF4J joined the party and improved where log4j was lacking. The new version of LOG4J is available for some time already and I didn’t have a chance to look at what if offers...

Sometimes it’s good to have an option to try something out on the live environment. Checking things against production like traffic is the most reliable way to gather real-life metrics. In this post, I’m going to try and set up spring cache with a toggle. It’ll be possible to turn it off and on duri...

On almost every job interview there are questions about frameworks, programming principles, maybe some coding or whiteboard architecting. On the other side, there is the way you work. Tools and skills you use on a daily basis which define how you work. No one really asks about those things but I fin...

At work, we are slowly breaking down the monolithic application into smaller manageable services. Some time ago we had a very interesting issue which proved that microservices are hard to implement. It’s especially true if you are not there yet but somewhere in the middle. When you need to introduce...

Some time ago we had a problem with performance caused by generating big reports for users. During one of the firehouse meetings, there was an idea to generate reports from the replica database. We’ve solved the issue differently but the idea got me interested. In this post, I’ll configure spring-bo...

You probably already know that by default in spring transactions are rolled back only for runtime exceptions. When a checked exception is thrown from your code and you don’t explicitly tell spring that it should rollback the transaction then it get’s committed. In this post, I’m going to create simp...

One thing that a lot of people hate to do is writing documentation. Usually, it’s postponed until development is finished and once it’s done there is rarely time to do it properly. If you get past the struggle of writing it down there is always a problem of keeping it up to date. To avoid those pain...

If you are not working with multithreading programming and don’t have to test any asynchronous code then this post will probably do you nothing good. But if you have ever struggled with testing some logic running in multiple threads and you don’t know Awaitility. A small library helps testing asynch...

Mocking library is an important tool in every developer toolbox. Sometimes you want to do things that at first glance look a bit more complex than returning number 42 from some method. Let’s see what stubbing techniques are available in Mockito out of the box and what they offer. Read more

We are improving cache in the project Im working on. In the code base I’ve found a method which accepted a collection of ids and returned collection of objects for those ids. My goal was to add cache on individual values returned by the method. Creation of items was IO heavy and time-consuming opera...

In the past, I’ve implemented couple of tests that aimed to verify naming conventions or some other practices team agreed upon. And presented a way how to ensure they are followed. When I’ve been writing those I was not aware that there is a library that aims to test architecture conventions - ArchU...

I’m learning python for some time now. I’ve made myself familiar with the syntax and then started looking into other ways to increase my knowledge about language and learn its quirks. I’ve found a very nice site that allows me to practice basics and strengthen different kind of muscles that I’m usin...

Recently I’ve found a very interesting project which allows to spin up docker containers for test purposes. Writing tests checking integration with external services is not an easy task. With testcontainers library it gets simpler because you can have external service up and running just for your te...

Recently I had to set up some extra logic to be executed before running tests. I had two options - create yet another abstract class with some behavior or somehow extend Spock and introduce extra logic to be executed just before actual test starts. As we already have enough of abstract classes I dec...

When the whole team agrees on coding standards we tend to be optimistic. We think that from now on everything will be exactly as we decided. The truth is that usually after a couple of months you’ll reinstall IDE or system and forget about configuration or new people join and it’s the Wild West all ...

Spring provides many easy to use abstractions and you use many of them without even knowing about them. You probably know that in order to have @Transactional or @Cacheable annotation work spring creates proxies for you (sometimes proxies on top of proxies…​), but have you ever wondered how it’s hap...

Version management in maven (especially in multi-module projects) was not pleasant and required multiple build steps, some magic commands and maybe bash script here and there. With version 3.5.0 new cool feature has been added to maven. From this version you can easily customize your build number fr...

In the past, I’ve been doing various things with maven. Some of them were standard, some were more complicated and a couple of them were complex. For those complex solutions, I felt like I needed a plugin but I’ve never had enough time to write it properly. In this post, I’m going to explore the bas...

How beans are registered in spring and what is the base of beans creation, how to extend spring’s context to our needs? In this post, I’m going to dig into the foundation of many mechanics in spring framework - bean definition. Read more

Some time ago I’ve faced a very interesting support issue. Long story short it turned out that one of our applications was not connecting to proper service and as a result, it’s been displaying invalid data to users. After a bit of investigation, I’ve noticed that spring’s configuration mechanism di...