Random musings of a software engineer.
When metrics aren't the whole story In the previous post , we set up metrics collection with Prometheus. We can now see what is happening on our devices — a sensor is failing, the WiFi signal is degrading, or the main loop is running slow. But metrics alone don't tell us why . When a device reboots, the uptime metric resets — but what caused the reboot? When an entity fails, the _failed…
What is observability and why does it matter? ESPHome is an amazing tool. Devices you build with it are very useful. But how do you notice when they don't work? You would eventually notice if a temperature sensor stopped working and your climate control automations aren't working as intended. While that's not ideal, it gets worse: what about a sensor part of an alarm system,…
When serving files with Ktor , there might be times when you need to alter those files. For example, you might want to inject a script in every served HTML file. For this purpose, we can leverage plugins . Plugins can hook at different stages of the request/response pipeline: graph LR Request --> Plugin1[Plugin] Plugin1 --> Handler Handler --> Plugin2[Plugin] Plugin2 --> Response Ktor…
Serving static files with Ktor for a static website seems easy enough: fun main () { embeddedServer (Netty, port = 8080 ) { routing { static { files ( "static-data" ) } } }. start (wait = true ) } Done? Not quite. Opening http://localhost:8080 will only get you a 404, even if you have an index.html file in the static-data folder. You have to let Ktor know you want to opt-in serving a…
This post will cover two things: How to run an arbitrary tool with Bazel (in this case, PlantUML , a tool to generate diagrams), by writing a rule set How to test this rule set. It should be mentioned that while I was working on this rule set, it became more and more apparent PlantUML is not a great candidate for this kind of integration, as its output is platform-dependent (the font rendering).…
This post will describe how to compile a small application written in Kotlin using Bazel , tests, as well as how to use static analyzers. Phosphorus Phosphorus is the application that this post will cover. It's a small utility that I wrote to check if an image matches a reference. If it doesn't, Phosphorus generates an image highlighting the differences. The goal is to be able to check…
In this post, we'll cover what Bazel is, how to use it, and why I chose to use it. What is Bazel? Bazel is a build-system released by Google in 2015. It actually is derived from the internal build-system Google uses internally for most of its own code-base, called Blaze . Building at scale Bazel has a huge focus on hermetic builds, and reproducibility. Every build step is, from a really broad…
This blog has been inactive for a long time. I tried to at least post an article yearly, and next thing you know, two years and a half fly by… Halloween seemed like a good time to resurrect it. I wanted to start writing again recently, and faced an issue: this blog was using Octopress 2. Well, Octopress has apparently been dead for even longer than this blog . So I wanted to switch to another…
Compat libraries are great. They allow us to work with the newest Android APIs, without thinking (much) about your minimum API level. Instead of thousands of devices, you can reach billions. With nearly no changes in your code. But sometimes, they're not so great…
What is Android Things? Android Things is an alternative Android version, announced at Google I/O 2015, and released as a first developer preview in December 2016. Its purpose is to develop embedded IoT devices, with a known and widely documented Android ecosystem basis. It's currently running on three different boards: the Intel Edison, the NXP Pico i.MX6UL, and the Raspberry Pi 3. Some…
With the Android M SDK (API 23), Google removed the Apache HTTP Client library. It was deprecated since API 22, and Google recommended to use HttpURLConnection instead since API 9. While the classes are still bundled in Android 6 ROMs, it won't be long until we see them completely go away. Some applications are still relying on this library, and need to be updated to use the SDK 23, without…
When writing an application, you probably want it to run on most platforms possible. Having a game on Android is great, but what about this weird friend with his iPhone? It would be nice to be able to play with him. Of course there are cross-platforms technologies like Cordova or Titanium . But sadly, you can't achieve both a perfect user experience and great performances with this kind of…
Introduction to RecyclerView RecyclerView has been introduced with Android 5, in the support-v7 package. It allows to display a collection of items in an arbitrary disposition (think of a ListView , but much more flexible). As the name of the support package indicates, it's available from the API level 7 (Android 2.1). Its name comes from the way it works: when an item is hidden, instead of…
Engine what? Nginx (engine-x) is a web server and reverse proxy for web and mail protocols (HTTP, HTTPS, SMTP, POP3 and IMAP). It has been first released in 2004, and its usage keeps growing ever since (according to Netcraft , it was hosting 14.47% of active sites in August 2014). It's capable of hosting many kinds of applications: static HTML pages PHP, using PHP-FPM Ruby on Rails and any…
A lot of websites are generating data which could be really useful outside a web browser. Having the weather shown on your smartphone's lock-screen, the delay until your next bus… How can we use this from an application? This article will explain what's behind these hidden data flows, and how to use them. For this purpose, I'll use Trakt.tv as an example. If you don't know it:…
When you have to manipulate audio or video on Android, being used to open-source software, you have a single name which comes directly to you: FFmpeg. However, FFmpeg is a C software, meant to be used as an executable, and not officially supporting Android. There are a lot of partial and/or out-of-date how-to out there on how to get FFmpeg running on Android, like halfninja's build .…
The Leonardo has a simple keyboard API . I needed a way to emulate a keyboard (from a joystick and arcade buttons - you see where I'm going now). Here's how I did it.
Issue When you want to display a dialog, you don't only need a context, you need an activity context. From an activity, displaying a dialog is pretty straightforward: Display a dialog from an activity new AlertDialog . Builder ( MyActivity . this ) . setTitle (" Dialog title ") . setMessage (" Dialog message ") . setPositiveButton ( android . R . string . yes , new DialogInterface .…