Tag: code

Rescuing broken MariaDB

May 8, 2026
valeblog
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As usual, my cluster is limited in resources (what you get for using the cheapest VPS available, I guess). Recently for whatever reason, one of my nodes has been constantly getting high IO and CPU warnings. As usual, this was caused by high swap activity due to memory exhaustion. The thing is, I didn’t really understand why that would suddenly start to happen.

Things (which may or may not be detailed in a later post) happened and I ended up wanting to migrate the MariaDB powering this blog to a different node. This is when all hell broke loose.

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Fixed my TLS

shallow focus photography of padlocks in steel cable
June 17, 2025
valeblog
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Usually there was no problem. Stuff worked just fine. Certificates were generated and renewed automatically. https:// links opened without ugly browser warnings about how you’re about to get hacked and it’s the end of the known universe.

But when it wasn’t “usually”, when Traefik just happened to restart for whatever reason, then all of that was obliterated. Since Traefik was running on ephemeral storage, eg nothing was really persisted, innocently tweaking some configuration (that resulted in a restart) could be catastrophic. You know, self-signed certificates and ugly browser warnings.

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Upgrading the argo-cd Helm chart from 5.x to 8.x

three sail boats on water during daytime
May 19, 2025
valeblog
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I’ve been using Argo CD for GitOps automation for a very long time. I have it manage itself too! The other day I noticed that there was a new major version of Argo CD, so I decided to upgrade my stuff too. It did not go smoothly, though it wasn’t an issue with Argo CD itself.

It was the usual problem of Helm charts renaming and moving around stuff in their values.yaml, which results in significant breakage for (from an user perspective) no good reason. I summed up what I learned so others don’t have to play around with it so much.

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The mythical modular monolith

Trees and snow are seen from above.
March 23, 2025
valeblog
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So often I see people giving talks about how the microservice architecture is a failure. You end up losing transactional protections, you’ll have to “join” data across a network boundary, and that network boundary is “always” flaky. Wouldn’t it be much better if everything was in one process, where you could enjoy the benefits of transactions, neighboring data is just a method call away and the only network you have to worry about is the database connection?

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Tricking the JVM JIT into speed

December 12, 2024
valeblog
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On the Clojurians Slack, PEZ brought some delicious Fibonacci performance tuning from the “languages” repo. While I don’t think that benchmark is as useful as mesmerizing the moving circles are in the animated graphs, I had a few very confusing and interesting discoveries.

Step 1: watch Alex Miller’s talk about Clojure’s interop performance. Step 2: learn how to actually do all that stuff. Step 3: notice that recursion does things. Step 4: magic.

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Untyped JS objects in ClojureScript

December 10, 2024
valeblog
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Working on a Chrome plugin I got to use ClojureScript in yet another new environment. After the usual browser setup, Node, Deno and Github Actions, this time it was the Chrome plugin system. While it was mostly a very smooth ride, I had a little trouble figuring out how to deal with a “Cannot infer target type in expression” warning.

It showed up while dealing with a HAR entry object passed in to my callback from devtools.network.onRequestFinished. The HAR object, while its shape is well defined, is not typed in a strict sense (though I guess there may be some type definition for it somewhere out there if I looked hard enough). That’s why when I tried to access its fields like (-> entry .-request .-url) the ClojureScript compiler (through Shadow CLJS) would complain about inferring the “target type” as above.

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ClojureDartで自前でwidget作ろうとするときの注意点

December 9, 2024
valeblog
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やりたかったことは多言語対応の一環だった。flutter_localizationsの生成コードでBuildContextからAppLocalizationは取得できるが、それと別にOSの言語設定を監視したかった。そのために他のウィジェットを包むだけのものを用意して、ミドルウェア的な挙動でOSの言語設定をアプリのDBに保管したかった。でもなぜかそれを適応すると、今度はgo_routerのStatefulShellRouteを使った遷移が機能しなくなってしまった。

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extend-protocolでClass/forName怒られるワケ

December 7, 2024
valeblog
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Clojureでプロトコルをよく使う。defprotocolで作ってextend-protocolで各種の型に実装すると、いろんな入力値にスムーズに対応できる。例えば暗号化周りで、ハッシュや署名の算出のためにバイト配列が必要な際、プロトコルを活かしていい感じのAPIが提供できる。

(defprotocol Byteish
  (->bytes ^bytes [input]))

(extend-protocol Byteish
  String
  (->bytes [input] (.getBytes input)))
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Some notes on iOS BLE

March 24, 2024
valeblog
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Dealing with Bluetooth Low Energy (BLE) through Swift can be pretty tricky. The interfaces and delegation are straightforward, but there is an implicit “right way” of doing things that (as far as I could find) is not documented anywhere.

I don’t know if the way you have to hold on to references to things or they get immediately discarded and cleaned up was surprising only for me with zero Swift background, but it took some time to get used to. For example CBPeripheral and CBL2CAPChannel objects require that you keep a reference to them, or the connection will be terminated, resulting in interesting behaviors.

Another thing is that I couldn’t find any details about error patterns in the documentation, but I figured out the following:

  • the input and output streams that come with a CBL2CAPChannel are not opened when you get your hands on them, and result in a pretty obscure 0x0122 failure if you try to use them without opening them first
  • you have to read/write those streams from the same DispatchQueue where they are scheduled, or the operations will silently just do nothing. Logging Thread.current can help debugging this.
  • error 436 means the local (you) severed the connection. This usually happens when you forget to hold on to the CBPeripheral instance
  • error 431 means the remote peer severed the connection. I’m not entirely sure what triggers this, since usually the disconnect is very graceful with a delegate callback. Maybe sometimes closing the streams doesn’t make it in time and this error gets logged first?
  • error 582 means the PSM used to initiate the CBL2CAPChannel is incorrect.

Longhorn trash weighing me down

December 8, 2023
valeblog
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Last year I gave Longhorn a try. It was a nice proposition for me: I was using local storage anyway, so the idea that pods would be independent of the nodes sounded delicious. Except the price was way too much.

At the time I thought that the only problem was Prometheus, which in itself is pretty heavy on disk IO, but it turns out the issue was with Longhorn itself. Also, as I found out, I wasn’t thorough enough deleting Longhorn stuff, which resulted in quite a few headaches this year.

white cow statue beside brown tree
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