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Broadcast devices' name on the local network
With years, I accumulated devices on my local network, which in general run on Linux. I meticulously added them to my /etc/hosts/ file, so as not to remember their IP. Something puzzled me, though: my Synology NAS was readily available as nas.local on the network, without doing anything. I have close to zero skills in system administration, so here are my findings. The .local domain We can learn more about .local domain from Wikipedia. The domain name .local is a special-use domain name r
Testing an OpenRewrite recipe
For the last two weeks, I’ve kicked the tires of OpenRewrite. At first, I created a recipe to move Kotlin source files as per the official recommendations with a set package name. I then improved the recipe to compute the root automatically. In both versions, I thoroughly tested the recipe. However, my testing approach was wrong. In this post, I want to describe my mistakes, and how I fixed them. The naive approach I originally approached the testing of the recipe in a very naive way, t
Improving my previous OpenRewrite recipe
I started discovering OpenRewrite last week by writing a Kotlin recipe that moves Kotlin files according to the official directory structure recommendation. I mentioned some future works, and here they are. In this post, I want to describe how to compute the root package instead of letting the user set it. Reminder I developed last week a recipe to follow the Kotlin recommendation regarding directory structure: In pure Kotlin projects, the recommended directory structure follows the packa
Authoring an OpenRewrite recipe
I’ve been eying OpenRewrite for some time, but I haven’t had time to play with it yet. In case you never heard about OpenRewrite, OpenRewrite takes care of refactoring your codebase to newer language, framework, and paradigm versions. OpenRewrite is an open-source automated refactoring ecosystem for source code, enabling developers to effectively eliminate technical debt within their repositories. It consists of an auto-refactoring engine that runs prepackaged, open-source refac
OpenRewrite recipes
I’ve been eying OpenRewrite for some time, but I haven’t had time to play with it yet. In case you never heard about OpenRewrite, OpenRewrite takes care of refactoring your codebase to newer language, framework, and paradigm versions. Using OpenRewrite is pretty straightforward. It already provides a large corpus of existing recipes, some of which are free. What I find amazingly powerful is the ability to author new recipes. I decided to learn about it and write my own in this serie
Authoring an OpenRewrite recipe
I’ve been eying OpenRewrite for some time, but I haven’t had time to play with it yet. In case you never heard about OpenRewrite, OpenRewrite takes care of refactoring your codebase to newer language, framework, and paradigm versions. OpenRewrite is an open-source automated refactoring ecosystem for source code, enabling developers to effectively eliminate technical debt within their repositories. It consists of an auto-refactoring engine that runs prepackaged, open-source refac
Runtime-initialized variables in Rust
Rust offers different ways to initialize compile time-initialized variables. Recently, I had to create a runtime-initialized variable: existing approaches don’t work in this case. I want to describe multiple ways to achieve it in this post. Constants The Rust language allows you to create constants. Two keywords are available: const and static. Sometimes a certain value is used many times throughout a program, and it can become inconvenient to copy it over and over. What’s more, it’
Writing for Developers
I started this blog as a hobby seventeen years ago, in April 2008. At the time, I had no clue about technical writing. I’m pretty sure it was not even a thing back then: the only content aimed at developers was technical documentation. Since then, the landscape has changed a lot, to the point that companies hire for technical writer positions. I was curious to compare what I learned by doing to the structured approach of a book. I ordered the book last year when it was still being written
Getting a single value from a device's state in Home Assistant
This is the 7th post in the My journey with Home Assistant focus series. I recently acquired Netatmo smart radiator valves to manage my rooms' temperature remotely. I’m not skilled at manual tasks, but I could easily replace the old thermo-static valves. I then registered the smart ones in the Netatmo app. Finally, I integrated them in my Home Assistant via the dedicated Netatmo integration. Everything was very straightforward. I noticed that each valve not only allows remote control but al
Getting my feet wet with Crossplane
In the early days of IT, we manually configured servers–each one a precious snowflake, lovingly maintained and documented. But the size of the infrastructure grew and this approach couldn’t scale. Chef and Puppet popularized the idea of Infrastructure-as-Code: engineers would define the state of the machine(s) in text files, stored in Git–hence the name. A global node would read these files to create a registry. Then, a local agent on each machine would check the desired state at regular in
The subtle art of waiting
Recently, while working on a workshop titled Testing Your Pull Request on Kubernetes with GKE, and GitHub Actions, I faced twice the same issue: service A needs service B, but service A starts faster than service B, and the system fails. In this post, I want to describe the context of these issues and how I solved them both with the same tool. Waiting in Kubernetes It might sound strange to wait in Kubernetes. The self-healing nature of the Kubernetes platform is one of its biggest benefits.
High-cardinality values for build flags in Rust
While working on my demo on WebAssembly and Kubernetes, I wanted to create three different binaries based on the same code: Native: compile the Rust code to regular native code as a baselineEmbed: compile to WebAssembly and use the WasmEdge runtime image as the base Docker imageRuntime: compile to WebAssembly, use a base scratch image as my base image, and set the runtime when running the code The code itself is an HTTP server that offers a single endpoint. For the sake of the demo, I wanted it
Even more OpenTelemetry - Kubernetes special
I have presented my OpenTelemetry demo many times, and I still do. Each time, the audience is different. To make no two presentations the same, I always ask attendees what stack they are more interested in. I also regularly add new features for the same reason. I was a victim of the IT crisis last summer, and my company fired me, so I no longer work on Apache APISIX. They say that the Chinese ideogram for crisis contains the ideogram for opportunity. I used this opportunity to join LoftLabs. Lo
Mutation Testing in Rust
I’ve been a big fan of Mutation Testing since I discovered PIT. As I dive deeper into Rust, I wanted to check the state of mutation testing in Rust. Starting with cargo-mutants I found two crates for mutation testing in Rust: cargo-mutantsand mutagen mutagen hasn’t been maintained for three years, while cargo-mutants is still under active development. I’ve ported the sample code from my previous Java code to Rust: struct LowPassPredicate { threshold: i32, } impl
Clean your Memory: From Finalize to Cleaner
Garbage collection in Java takes care of memory management, but it does not clean up non-memory resources like sockets or file handles. Resource leaks may occur without proper management, leading to performance degradation or crashes. Java’s Cleaner API, introduced in Java 9, provides a modern and efficient mechanism for resource cleanup when objects are no longer reachable. It addresses the shortcomings of the deprecated finalize() method, offering a predictable and efficient way to manage
One giant Kubernetes cluster for everything
The ideal size of your Kubernetes clusters is a day 0 question and demands a definite answer. You find one giant cluster on one end of the spectrum and many small-sized ones on the other, with every combination in between. This decision will impact your organization for years to come. Worse, if you decide to change your topology, you’re in for a time-wasting and expensive ride. I want to list each approach’s pros and cons in this post. Then, I’ll settle the discussion once a
Improving Maven's dependency:analyze... or not
Recently, my good friend Richard Fichtner advised using the mvn dependency:analyze command to get rid of declared but unused dependencies: There is another use case for mvn dependency:analyze It can show you the dependencies you use in your code but have not declared in your pom.xml. This works because you have a transitive dependency on your classpath. Either don't use the dependency or declare it.[image or embed]— Richard Fichtner 💻☕ (@richard.fichtner.dev) December 10, 2024 at 2:
WebAssembly on Kubernetes
Like a couple of innovative technologies, different people have different viewpoints on where WebAssembly fits the technology landscape. WebAssembly (also called Wasm) is certainly the subject of much hype right now. But what is it? Is it the JavaScript Killer? Is it a new programming language for the web? Is it (as we like to say) the next wave of cloud compute? We’ve heard it called many things: a better eBPF, the alternative to RISC V, a competitor to Java (or Flash), a performance booster
Pull request testing on Kubernetes: vCluster for isolation and costs control
This week’s post is the third and final in my series about running tests on Kubernetes for each pull request. In the first post, I described the app and how to test locally using Testcontainers and in a GitHub workflow. The second post focused on setting up the target environment and running end-to-end tests on Kubernetes. I concluded the latter by mentioning a significant quandary. Creating a dedicated cluster for each workflow significantly impacts the time it takes to run. On GKE, it t
Pull request testing on Kubernetes
Imagine an organization with the following practices: Commits code on GitHubRuns its CI/CD pipelines with GitHub ActionsRuns its production workload on KubernetesUses Google Cloud A new engineer manager arrives and asks for the following: On every PR, run integration tests in a Kubernetes cluster similar to the production one. It sounds reasonable. Engineering manager: I want #integrationtests to run on the app deployed on #Cloud infra for each #GitHub PR ✅ Me, thinking it's a no
Pull request testing on Kubernetes: testing locally and on GitHub workflows
Imagine an organization with the following practices: Commits code on GitHubRuns its CI/CD pipelines with GitHub ActionsRuns its production workload on KubernetesUses Google Cloud A new engineer manager arrives and asks for the following: On every PR, run integration tests in a Kubernetes cluster similar to the production one. It sounds reasonable. Engineering manager: I want #integrationtests to run on the app deployed on #Cloud infra for each #GitHub PR ✅ Me, thinking it's a no
Pull Request testing on Kubernetes: working with GitHub Actions and GKE
I’m continuing my series on running the test suite for each Pull Request on Kubernetes. In the previous post, I laid the groundwork for our learning journey: I developed a basic JVM-based CRUD app, tested it locally using Testcontainers, and tested it in a GitHub workflow with a GitHub service container. This week, I will raise the ante to run the end-to-end test in the target Kubernetes environment. For this, I’ve identified gaps that I’ll implement in this blog post: Create
Remote Development made simple with DevPod
I come relatively late to the subject of Remote Development Environments (also known as Cloud Development Environments). The main reason is that I haven’t worked in a development team for over six years. However, I’m now working for Loft Labs, and we have a RDE product: DevPod. I wanted to understand our value proposition as I’ll be at FOSDEM operating the DevPod booth. The problem As a former developer, I vividly remember the pain of setting up each developer’s develo
On inheritance and subtyping
Java is the first language I learned in my career. Its structure is foundational in my early years of understanding programming concepts. After going through several other languages with very different approaches, I’ve widened my point of view. Today, I want to reflect on the idea of inheritance. Inheritance in Java In Java, the idea of inheritance is tightly coupled with the concept of subtyping. Subtyping is the implementation of a IS A relationship. For example, the Rabbit class is a
My first steps with Playwright
In my previous company, I developed a batch job that tracked metrics across social media, such as Twitter, LinkedIn, Mastodon, Bluesky, Reddit, etc. Then I realized I could duplicate it for my own 'persona'. The problem is that some media don’t provide an HTTP API for the metrics I want. Here are the metrics I want on LinkedIn: I searched for a long time but found no API access for the metrics above. I scraped the metrics manually every morning for a long time and finally decided to au
The Home Assistant companion app
Besides a regular webapp and a Mac app, which uses the same endpoints as the webapp, Home Assistant also provides mobile apps. In this post, I want to describe its advantages over the former. I’ll use iOS to do this: Samsung’s French partner to recycle used mobiles tricked me once, and I moved away from Samsung. I decided to buy Apple for better integration since I’ve had Mac computers for the last few years. Installing and configuring The companion app is readily available
2024 in retrospective
For the first post of 2025, I’m continuing my retrospective series. As last year, before diving in into the report proper, I’d like to remind you that Ukraine is still fighting for its survival after nearly 3 years and countless Russian war crimes. The civilized world can’t allow rewarding the invasion of a sovereign country, lest we see more invasions. Remember that in 1938, in Munich, European 'leaders' acknowledged Hitler’s annexation of Czechoslovakia’s Sudeten
An example of HACS: Adaptive Lighting
In the previous post of this focus, we replaced Philips Hue automation with the one from Home Assistant. One significant gap we noticed was that Home Assistant doesn’t automatically adjust the brightness according to the time of the day, a feature Philips Hue offers. In this post, we are going to address this gap. The first step when wanting to add a feature to Home Assistant is to browse through available integrations. While there was no out-of-the-box integration, I discovered an altern
A solution to the problem of cluster-wide CRDs
I’m an average Reddit user, scrolling much more than reading or interacting. Sometimes, however, a post rings a giant red bell. When I stumbled upon If you could add one feature to K8s, what would it be?, I knew the content would be worth it. The most voted answer is: Namespace scoped CRDs A short intro to CRDs Kubernetes comes packed with existing objects, such as Pod, Service, DaemonSet, etc., but you can create your own: the latter are called Custom Resource Definitions. Most o
Replace Philips Hue automation with Home Assistant's
This is the 3rd post in the My journey with Home Assistant focus series. I’m the happy owner of a couple of Philips Hue connected lights for a some years. Some of them are colored, some of them regular. In addition, I bought a sensor to go along with the light I installed in my toilets: it turns on automatically when its detects a movement there. In this post, I want to document how I replaced the proprietary automation with Home Assistant’s.
The Home Assistant model
Home Assistant is a massive beast. It can be overwhelming for a newcomer; it was for me. In this post, I want to describe the underlying model of Home Assistant, which is a good entry point for your home automation journey. The biggest issue in describing the Home Assistant is the number of conflicting sources for this model: The helpers package of the GitHub repositoryThe database; disclaimer: I didn’t find the schema generation in the code, and I wasn’t bold enough to check the d
Why Home Assistant?
This is the 1st post in the My journey with Home Assistant focus series. Last June, I spoke at Berlin Buzzwords. In all honesty, I rarely attend others' talks for a variety of reasons: lack of time, lack of energy, no interest in the proposed subjects, etc. When I do, I go either for subjects I know and want to deepen my understanding of or for subjects I know nothing about to get a foot in the door. This time, I attended Monitoring your home, with DevOps observability tools. I thought it would b
Pseudo-Random Number Generators: From the Origins to Modern Algorithms
How can we generate a uniform sequence of random numbers? The randomness so beautifully and abundantly generated by nature has not always been easy for humans to extract and quantify. Pseudo-Random Number Generators are fundamental tools in many areas of software development: PRNGs do not produce truly random numbers but rather deterministic sequences that simulate randomness. The quality of a PRNG is determined by its ability to produce sequences that are statistically indistinguishable from t
Langchain4J musings
I’m coming relatively late to the LLM party, but I rarely come very early in the hype cycle. For example, I never bought into blockchain, the solution still searching for problems to solve, nor in microservices, the latest in the cargo cult IT trends. Despite my late arrival at the LLM party, I have been a regular user of LLMs. I use OpenAI for non-controversial questions outside my cone of knowledge, e.g., linguistics or legal; I use GitHub Copilot in my IDE to improve my code. Th
DuckDB in Action
The book was sent to me by Michael Simons. He asked for my feedback: I changed my reading schedule, took a few months, and here it is. Facts 10 chapters288 pages$33.59 (eBook) Note that MotherDuck, a company providing an online service that builds upon DuckDB, offers a free PDF copy. Chapters An introduction to DuckDBGetting started with DuckDBExecuting SQL queriesAdvanced aggregation and analysis of dataExploring data without persistenceIntegrating with the Python ecosystemDuckDB in the
Digital Twins: A digital counterpart for a new concept of Product
Digital Twins, are digital replicas of physical assets, processes, or systems used to simulate, monitor, and optimize their real-world counterparts. Through real-time data exchange and advanced analytics, digital twins provide a virtual environment for testing scenarios, predicting outcomes, and enhancing decision-making. This concept, first introduced by Michael Grieves in 2002, has rapidly evolved and now plays a crucial role in various sectors, including manufacturing, healthcare, smart cities
Summary of the AJAX frameworks comparison
In previous weeks, I’ve analyzed several libraries and frameworks that augment the client with AJAX capabilities. Vue.jsAlpine.jsHTMXVaadin In this post, I’ll compare them across several axes. Analysis Frontend skills Remember that I started this series from the point of view of a backend developer. In this section, I grade how much you need to know about client technologies to complete the job. Team organization In the introduction, I hinted that the decoupling of frontend
Vaadin, the battery-included server-side AJAX framework
I’ve written a lot about Vaadin. I was so enthusiastic that I wrote the first book about it (besides the Book of Vaadin), its updated edition for Vaadin 7, and a companion website. Still, I’m amazed that so many people in the JVM world never heard of it. In this post, I’d like to introduce Vaadin in the context of AJAX and SSR. Short introduction to Vaadin The beauty of Vaadin lies in its simplicity - you only write backend code. You read that well. A Vaadin developer only