Posts on Haim Gelfenbeyn's Blog

Duplicating HTTP status in the response body is an anti-pattern

Sun, 02 Apr 2023 00:00:00 +0000

In this blog post, I discuss the use of HTTP response status codes and the potential issues with duplicating them in the response body, as well as how RFC7807 provides a solution for conveying application-specific errors.

Sometimes, I see APIs where the error response looks like this (HTTP header and body):

HTTP/1.1 400 Bad Request
Content-Type: application/json

{
 "status": 400,
 "message": "Foo is blank"
}

The HTTP response status code is duplicated in the body of the response. There are different reasons why people think this is a good idea:

Programming in Go is surprisingly productive

Fri, 07 Oct 2022 00:00:00 +0000

In my work life I’m involved with projects in Ruby, Python, Swift, Rust, Javascript, Typescript. I don’t have strong programming language preferences and believe in the “right tool for the job” approach: the language should be a good fit for a problem domain, team expertise, time/budget constrains, etc. Rust is my go-to language when high-performance, strong type safety, rich ecosystem, compiled language is required.

Go is often suggested in similar circumstances, and I’ve read a couple Go books, but I could never understand why someone would prefer Go to Rust: Rust is much safer, much richer language; Rust’s strict and pedantic compile-time checks help avoid whole classes of bugs that could bite you in Go. Even when the features are quite similar (error checking), Rust approach (? operator) is elegant and makes the code so much easier to read.

Run-once Kubernetes DaemonSet pods

Sat, 01 Jan 2022 00:00:00 +0000

Sometimes there’s a need to run some code just once, but on each node in your Kubernetes cluster: collecting some immutable node information is a prime use case. For example, for my Floating IP controller I need to collect the Anchor IP address on every node. See my previous post for context.

Kubernetes does not support this out-of-the box: DaemonSet supports only RestartPolicy of Always, so any pod that stops will be started immediately again. There are workarounds documented only, but they all rotate around the idea of having something lightweight running all the time on the node, to satisfy Kubernetes restart policy. This strikes me as inelegant.

Integrating DigitalOcean floating IPs with Kubernetes

Thu, 30 Dec 2021 00:00:00 +0000

The problem

DigitalOcean Kubernetes platform is great. Its Load Balancer is well-integrated and works great, too, unless you need to expose UDP services in your cluster: UDP load balancing is not supported! So it’s not possible to load-balance DNS, HTTP/3 or any other UDP service.

How are we going to solve this?

DigitalOcean supports floating IPs: publicly-accessible static IP addresses that you can assign to Droplets and instantly remap between other Droplets in the same datacenter.

Redundant first-hop router with Raspberry Pi

Wed, 30 Dec 2020 00:00:00 +0000

In my house, I’m using a general-purpose Linux machine as router. This is a much more flexible setup than using a dedicated device, it provides numerous benefits comparing to using a dedicated router, but it did pose a unique challenge: my router is actually a VM, not a physical machine: the host’s LAN carries multiple VLANs and the router/firewall VM just passes traffic between them.

This works great, but introduces multiple additional points of failure, comparing to a dedicated hardware router, the VM host being the biggest one. It needs to be updated/patched from time to time, and I didn’t want to end up without Internet/DNS/DHCP at that time. And here comes the idea of using a Raspberry Pi as a “backup” router when my main one is down for whatever reason.

Linking Swift code into a Rust app

Thu, 10 Sep 2020 00:00:00 +0000

Why would you want to do that?

I initially wrote my “KVM replacement” display-switch application twice, in Rust and Swift. The primary reason was that there is no MacOS-compatible DDC/CI control library for Rust. However, as the app became somewhat popular, and I wanted to add new features and improvements, I realized that this is not sustainable: I would have to implement every new feature twice.

So I thought: what if I extract only the MacOS-compatible DDC control Swift code as a separate library, and statically link it into the main Rust application?

Signing and notarizing a Python MacOS UI application

Sat, 08 Aug 2020 00:00:00 +0000

Why write a MacOS application in Python?

Python has an amazingly rich ecosystem of libraries, tools and frameworks. It is a clean, modern language, it allows for rapid prototyping and quick development cycles. UI was not the central, focal point of my app, so it made a lot of sense for me to do it in Python: I thought I’d write the core functionality first, and add the UI afterwards.

Dual-monitor 4K@60hz KVM switch for $30

Tue, 28 Jul 2020 00:00:00 +0000

The need for KVM

I like my two big hi-res monitors. I love my keyboard and my mouse. And I connect them to my stationary “main” PC and to several other Windows and Mac laptops, alternatively. I’d like to easily switch where these peripheral devices are connected to, and that’s the traditional role of a KVM switch.

Unfortunately for me, KVM switches that support 4K/60hz resolutions cost hundreds of dollars, there are no KVM switches that support USB-C, and I couldn’t find KVM switches that support multiple high-res monitors either.

Fresh air with ESP8266 and Home Assistant (part 2)

Sun, 26 Apr 2020 00:00:00 +0000

This is the second post about hooking up Heat Recovery Ventilator to Home Assistant. Previously, I wrote about the hardware aspect and here I’ll discuss the software that is needed to make it all work.

ESP8266 Firmware

There are several IoT frameworks available for ESP8266. I’ve decided to build my solution on top of Homie for ESP8266.

Homie is a thin and simple MQTT convention for the IoT, it integrates very well with Home Assistant and supports advanced features like initial setup of devices and OTA firmware updates. Homie implementation for ESP8266 is well-designed and is a pleasure to work with.

Fresh air with ESP8266 and Home Assistant (part 1)

Sat, 25 Apr 2020 00:00:00 +0000

This is the first post in a series about how I implemented MQTT controller for a Heat Recovery Ventilator (HRV) in my house, and hooked it up to my home automation system.

What is HRV?

Our house is quite new, and therefore pretty well sealed. In order to maintain a healthy interior climate and not lose too much energy in a cold Canadian climate, we have a Heat Recovery Ventilator system, which is a system that brings in fresh outdoor air and heats (or cools) it with an interior air it exhausts, thus reducing energy costs.

Automating "lunch" Slack status

Sat, 18 Apr 2020 00:00:00 +0000

Why?

My work is 100% remote, I work from home most of the time. Although I usually have a stable schedule and try to have meals at the same time every day, sometimes meetings get into way, and I eat earlier or later than usual. To let my co-workers know that I’m currently away, I prefer to set a Slack status (and do not send messages saying “going to lunch” and “back”).

Wall-mounted Dashboards (part 3)

Mon, 13 Apr 2020 00:00:00 +0000

This is the third article in a series about my DIY approach to wall-mounted home automation dashboards.

Choosing the dashboard platform

The “heart” of my home automation system is Home Assistant, an open source home automation platform written in Python. Its built-in web frontend is suitable for a dashboard, but only if the only thing you want to control is Home Assistant. I knew from the start that there were going to be several custom components in my dashboard, so my primary requirement was ease of development and personal familiarity.

Wall-mounted Dashboards (part 2)

Sat, 14 Mar 2020 00:00:00 +0000

This is the second article in a series of articles about my DIY approach to wall-mounted home automation dashboards. See the first part for initial planning, hardware, mounting and power supplies.

A big disappointment

My initial idea was to build an intercom system with these tablets. This turned out to be a bad idea, for two reasons:

Tablet’s microphone and speaker quality: They were pretty bad! I did some initial testing with various open-source Android softphones, and you had to stand pretty close to the tablet for the mike to pick up anything reliably, and the speakers were pretty weak! The fact that they are on the back of the tablet, facing the wall, didn’t help at all.

Wall-mounted Dashboards (part 1)

Sat, 07 Mar 2020 00:00:00 +0000

This is the first article in a series of articles about my DIY approach to wall-mounted home automation dashboards. This is a bit old news for us, as I completed this project 2 years ago. I didn’t want to write about it immediately after completion, I wasn’t sure how reliable the whole system is. However, today, two years later, it’s still 100% operational, so it’s time!

The objective

After we moved to a new house, I mentioned in passing to my wife that I would like to be able to control the various aspects of our house from a wall-mounted touch panel. To my surprise, this idea was well-received, and in fact the scope of the project become much larger than I initially planned. So we wanted: