Invention, mother of necessity

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The Milk Watcher: a Platonic Ideal for Operational Software
Sep 24, 2020

Recently I learned about the milk watcher, a nifty little device that helps you prevent overboils when you’re scalding milk (if you’ve ever heated up milk on a stovetop, you’ve no doubt experienced that terrifying moment when you leave it on the heat just a smidge too long and it foams up over the sides of the pan and cascades onto the burner).

The milk watcher is just a specially shaped disk of metal, glass, or ceramic, that you put at the bottom of the pan of milk you’re heating, where it serves two purposes:

  1. As the milk starts to boil, the milk watcher rattles around against the bottom of the pan, alerting you to that fact so you can come tend to it
  2. The special shape of the milk watcher traps gas and releases it as a large bubble, and these larger bubbles can break the tension at the surface of the milk (which smaller, naturally-occurring bubbles cannot) and prevent catastrophic boil-over

I love everything about this device, and it seems to me to be a kind of Platonic ideal for operational software to attain to, in that it has all the following qualities:

  • It’s cheap
  • It’s robust—it basically can’t break
  • It’s simple—it’s nearly impossible to mis-use
  • It does only one job, and its design and purpose resist any increase in responsibilities
  • It both monitors for / alerts on brewing problems, and attempts to prevent / mitigate those problems

If I ever start or work at a DevOps company, I’m totally handing out branded milk watchers as swag.

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