Misc

I always get tripped up by Docker’s different mount types and their syntax, whether I’m stringing together some CLI commands or writing a docker-compose file. Docker’s docs cover these, but for me, the confusion often comes from how “bind” is used in various contexts and how “volume” and “bind” sometimes get mixed up in the documentation. Here’s my attempt to disentangle some of my most-used mount commands. Volume mounts Volume mounts1 let you store data outside the container in a location managed by Docker. The data persists even after the container stops. On non-Linux systems, volume mounts are faster than bind mounts because data doesn’t need to cross the virtualization boundary. ...

I’m not really a fan of shims—code that automatically performs actions as a side effect or intercepts commands when you use the shell or when a prompt runs. That’s why, other than the occasional dabbling, I’ve mostly stayed away from tools like asdf or pyenv and instead stick to apt or brew for managing my binary installs, depending on the OS. Recently, though, I’ve started seeing many people I admire extolling direnv: ...

I spent the evening watching this incredibly grokkable talk on event-driven services by James Eastham at NDC London 2024. Below is a cleaned-up version of my notes. I highly recommend watching the full talk if you’re interested before reading this distillation. The curse of tightly coupled microservices Microservices often start with HTTP-based request-response communication, which seems straightforward but quickly becomes a pain as systems grow. Coupling—where one service depends on another—creates a few issues. Take the order processing service in a fictional Plant-Based Pizza company. It has to talk to the pickup service, delivery service, kitchen, and loyalty point service. They’re all tied together, so if one fails, the whole system could go down. ...

While going through a script at work today, I came across Bash’s nameref feature. It uses declare -n ref="$1" to set up a variable that allows you to reference another variable by name—kind of like pass-by-reference in C. I’m pretty sure I’ve seen it before, but I probably just skimmed over it. As I dug into the man page1, I realized there’s a gap in my understanding of how variable references actually work in Bash—probably because I never gave it proper attention and just got by cobbling together scripts. ...

When I started writing here about five years ago, I made a promise to myself that I wouldn’t give in to the trend of starting a blog, adding one overly enthusiastic entry about the stack behind it, and then vanishing into the ether. I was somewhat successful at that and wanted to write something I can link to when people are curious about the machinery that drives this site. The good thing is that the tech stack is simple and has remained stable over the years since I’ve only made changes when absolutely necessary. ...

I always struggle with the syntax for redirecting multiple streams to another command or a file. LLMs do help, but beyond the most obvious cases, it takes a few prompts to get the syntax right. When I know exactly what I’m after, scanning a quick post is much faster than wrestling with a non-deterministic kraken. So, here’s a list of the redirection and piping syntax I use the most, with real examples. ...

I learned this neat Bash trick today where you can make a raw HTTP request using the /dev/tcp file descriptor without using tools like curl or wget. This came in handy while writing a health check script that needed to make a TCP request to a service. The following script opens a TCP connection and makes a simple GET request to example.com: #!/bin/bash # Open a TCP connection to example.com on port 80 and assign file descriptor 3 # The exec command keeps /dev/fd/3 open throughout the lifetime of the script # 3<> enables bidirectional read-write exec 3<>/dev/tcp/example.com/80 # Send the HTTP GET request to the server # >& redirects stdout to /dev/fd/3 echo -e "GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n" >&3 # Read and print the server's response # <& redirects the output of /dev/fd/3 to cat cat <&3 # Close the file descriptor, terminating the TCP connection exec 3>&- Running this will print the response from the site to your console. ...

TIL about the install command on *nix systems. A quick GitHub search for the term brought up a ton of matches1. I’m surprised I just found out about it now. Often, in shell scripts I need to: Create a directory hierarchy Copy a config or binary file to the new directory Set permissions on the file It usually looks like this: # Create the directory hierarchy. The -p flag creates the parent directories # if they don't exist mkdir -p ~/.config/app # Copy the current config to the newly created directory. Here, conf already # exists in the current folder cp conf ~/.config/app/conf # Set the file permission chmod 755 ~/.config/app/conf Turns out, the install command in GNU coreutils2 can do all that in one line: ...

I was working on the deployment pipeline for a service that launches an app in a dedicated VM using GitHub Actions. In the last step of the workflow, the CI SSHs into the VM and runs several commands using a here document1 in bash. The simplified version looks like this: # SSH into the remote machine and run a bunch of commands to deploy the service ssh $SSH_USER@$SSH_HOST <<EOF # Go to the work directory cd $WORK_DIR # Make a git pull git pull # Export environment variables required for the service to run export AUTH_TOKEN=$APP_AUTH_TOKEN # Start the service docker compose up -d --build EOF The fully working version can be found on GitHub2. ...

One of the reasons why I’m a big advocate of rebasing and cleaning up feature branches, even when the changes get squash-merged to the mainline, is that it makes the PR reviewer’s life a little easier. I’ve written about my rebase workflow before1 and learned a few new things from the Hacker News discussion2 around it. While there’s been no shortage of text on why and how to craft atomic commits3, I often find those discussions focus too much on VCS hygiene, and the main benefit gets lost in the minutiae. When working in a team setup, I’ve discovered that individual commits matter much less than the final change list. ...

People tend to get pretty passionate about Git workflows on different online forums. Some like to rebase, while others prefer to keep the disorganized records. Some dislike the extra merge commit, while others love to preserve all the historical artifacts. There’s merit to both sides of the discussion. That being said, I kind of like rebasing because I’m a messy committer who: Usually doesn’t care for keeping atomic commits1. Creates a lot of short commits with messages like “fix” or “wip”. Likes to clean up the untidy commits before sending the branch for peer review. Prefers a linear history over a forked one so that git log --oneline --graph tells a nice story. Git rebase allows me to squash my disordered commits into a neat little one, which bundles all the changes with passing tests and documentation. Sure, a similar result can be emulated using git merge --squash feat_branch or GitHub’s squash-merge feature, but to me, rebasing feels cleaner. Plus, over time, I’ve subconsciously picked up the tricks to work my way around rebase-related gotchas. ...

People typically associate Google’s Protocol Buffer1 with gRPC2 services, and rightfully so. But things often get confusing when discussing protobufs because the term can mean different things: A binary protocol for efficiently serializing structured data. A language used to specify how this data should be structured. In gRPC services, you usually use both: the protobuf language in proto files defines the service interface, and then the clients use the same proto files to communicate with the services. ...

One neat use case for the HTTP ETag header is client-side HTTP caching for GET requests. Along with the ETag header, the caching workflow requires you to fiddle with other conditional HTTP headers like If-Match or If-None-Match. However, their interaction can feel a bit confusing at times. Every time I need to tackle this, I end up spending some time browsing through the relevant MDN docs123 to jog my memory. At this point, I’ve done it enough times to justify spending the time to write this. ...

Every once in a while, I find myself skimming through the MDN docs to jog my memory on how CORS1 works and which HTTP headers are associated with it. This is particularly true when a frontend app can’t talk to a backend service I manage due to a CORS error2. MDN’s CORS documentation is excellent but can be a bit verbose for someone just looking for a way to quickly troubleshoot and fix the issue at hand. ...

I love dynamically typed languages as much as the next person. They let us make ergonomic API calls like this: import httpx # Sync call for simplicity r = httpx.get("https://dummyjson.com/products/1").json() print(r["id"], r["title"], r["description"]) or this: fetch("https://dummyjson.com/products/1") .then((res) => res.json()) .then((json) => console.log(json.id, json.type, json.description)); In both cases, running the snippets will return: 1 'iPhone 9' 'An apple mobile which is nothing like apple' Unless you’ve worked with a statically typed language that enforces more constraints, it’s hard to appreciate how incredibly convenient it is to be able to call and use an API endpoint without having to deal with types or knowing anything about its payload structure. You can treat the API response as a black box and deal with everything in runtime. ...

I like writing custom scripts to automate stuff or fix repetitive headaches. Most of them are shell scripts, and a few of them are written in Python. Over the years, I’ve accumulated quite a few of them. I use Git and GNU stow1 to manage them across different machines, and the workflow2 is quite effective. However, as the list of scripts grows larger, invoking them becomes a pain because the tab completion results get cluttered with other system commands. Plus, often I even forget the initials of a script’s name and stare at my terminal while the blinking cursor facepalms at my stupidity. ...

I’m one of those people who will sit in front of a computer for hours, fiddling with algorithms or debugging performance issues, yet won’t spend 10 minutes to improve their workflows. While I usually get away with this, every now and then, my inertia slithers back to bite me. The latest episode was me realizing how tedious it is to move config files across multiple devices when I was configuring a new MacBook Air and Mac Mini at the same time. ...

This site1 is built with Hugo2 and served via GitHub pages3. Recently, I decided to change the font here to make things more consistent across different devices. However, I didn’t want to go with Google Fonts for a few reasons: CDN is another dependency. Hosting static assets on GitHub Pages has served me well. Google Fonts tracks users and violates4 GDPR in Germany. Google Analytics does that too. But since I’m using the latter anyway, this might come off a bit apocryphal. I wanted to get a few extra Lighthouse points. Turns out, it’s pretty easy to host the fonts yourself. ...

This morning, while browsing Hacker News, I came across a neat trick1 that allows you to share textual data by leveraging DNS TXT records. It can be useful for sharing a small amount of data in environments that restrict IP but allow DNS queries, or to bypass censorship. To test this out, I opened my domain registrar’s panel and created a new TXT type DNS entry with a base64 encoded message containing the poem A Poison Tree by William Blake. The message can now be queried and decoded with the following shell command: ...

This weekend, I was working on a fun project that required a fixed-time job scheduler to run a curl command at a future timestamp. I was aiming to find the simplest solution that could just get the job done. I’ve also been exploring Google Bard1 recently and wanted to see how it stacks up against other LLM tools like ChatGPT, BingChat, or Anthropic’s Claude in terms of resolving programming queries. ...