Debugging

My deploy ran my tests, and my tests ran my deploy

My desktop ran out of memory five times in two days, once killing 29,082 processes at a stroke. Two files that were each sensible on their own had made a loop with no way out.

Wednesday, October 21, 2026 | 6 min read Read

A memory limit made Grafana hammer the disk

Grafana stalled for minutes while the host had more than 4 GB of memory available. The clue that it was starving for memory was the NVMe reading 1.7 GB a second.

Sunday, October 18, 2026 | 5 min read Read

A third of my request was the garbage collector

A slow grid in a Flask app I maintain had an obvious suspect. The biggest cost was Python re-checking 134,000 objects that would never be freed.

Friday, October 9, 2026 | 7 min read Read

The date that was yesterday until 3am

A one-line date bug that only existed between midnight and 03:00, in an app whose heaviest users work nights. Then my fix for it turned out to be wrong in two of the three places I applied it.

Friday, September 11, 2026 | 3 min read Read

The badge that said 21 for a count of 1

I added a small shield badge showing how many months someone had won a challenge. On my own profile, with one win, it said 21. The sample render I had checked it against said 1.

Monday, September 7, 2026 | 2 min read Read

Safari could not download the file

A download button in an app I maintain failed on a Mac with WebKitBlobResource error 1. The fix was to delete code: the server had been able to do the job by itself all along.

Wednesday, September 2, 2026 | 2 min read Read

The scanner that was never broken

The scan half of my HP OfficeJet had never worked from this machine, and I'd filed that under driver problems. No driver was needed. There was no scanner software installed at all, and the real mistakes started after I installed some.

Sunday, August 30, 2026 | 5 min read Read

The 144 Hz monitor that preferred 60

My 144 Hz panel ran at 60 from the day the machine was built, and again after a graphics card swap. Different cause each time, and nothing reported a problem.

Friday, August 28, 2026 | 7 min read Read

I wrote the lesson down. I broke it two days later.

My project keeps a lessons-learned file. Going back through my notes, I found the same pattern five times: the lesson gets written down, and the repeat comes anyway.

Wednesday, August 5, 2026 | 5 min read Read

Hugo's module.mounts quietly replaced my static directory

Every deploy was green, every page worked, and one file returned 404 in production. The cause was a Hugo module mount behaviour that is documented but easy to miss.

Thursday, July 23, 2026 | 3 min read Read

The particle fade that never faded

I wrote fade-out code for explosion particles in a Pygame project, and it looked fine to me for months. It never faded once, and the reason is a quiet rule about how Pygame draws.

Sunday, January 26, 2025 | 4 min read Read