Duct tape enough services together and you can cache APT packages

Due to the current job market, I’ve had a bit more free time on my hands than usual so I have been spending more time on personal projects. Putting more effort into those projects sitting forever on the "I'll fix that eventually" list. The small kind of things that come up enough to notice but not important enough to focus on. One of those things was the APT cache I’ve been running. It generally works, but every so often it just randomly starts returning HTTP 500 errors without any useful logs and usually fixed by restarting it. How hard could it be? While spending a couple hours looking into it, not making much progress, I saw that I am not the only person having reliability issues with apt-cacher-ng. Scrolling through the Debian bug tracker, the application having errors caused by race conditions, incomplete downloads, and corrupted files seems to have become a frequent issue¹²³⁴⁵ in the last couple years with similar sounding issues going back over a decade. There are a few other al