Articles

Longer pieces on monitoring, and on the parts of it that are harder than they look.

Why certificates still lapse, twelve years after Let's Encrypt

Renewal is automated almost everywhere and certificates still expire in production. The failure has moved: it is no longer the renewal that breaks, it is everything between the renewal and the socket a browser actually connects to.

article 4 min read

Two nulls are not zero

A monitoring dashboard has three ways of not knowing something, and every one of them has been drawn as a confident zero at least once. Here is why that is the most expensive bug a status screen can have.

article 5 min read